Maintaining Alkali Bees

Alcalfa Seed Production

by W. P. Stephen

Station Bulletin 568 January 1959

Agricultural Experiment Station Oregon State College Corvallis Maintaining Alkali Bees ,Jaëja Seed Pwdeeioe

Pages '7,'e9àt Oeei The alkali bee is found primarily in the desert areas west of the Rocky Mountains. With the specialization in alfalfa seed production in this area, the bee has increased in numbers, and has assumed a major role for maintaining high seed yields-----3-4 4ieQtt The alkali bee has one generation per year. it spends the winter as a prepupae, emerging in spring. Females begin constructing new tunnels for next year's brood during the summer, securing pollen and nectar primarily from nearby alfalfa fields. 4-11

Availability of suitable nesting sites restricts widespread bee expansion. Bees depend on soils with specific texture and moisture, so subsoil water is able to rise and maintain a moist, compact soil surface. Farmers can help maintain and even cre- ate acceptable bee nesting sites. 11-15 T#taeee4ede O4Uei9... Greatest alkali bee loss has been indiscriminate use of highly toxic organic insecticides. 16

The bee fly, conopid fly, phorid fly, and tiger beetles have attacked and reduced alkali bee populations. 16-20

g'4eeeea amd i4ea4e4 Several bacteria and fungi have been noted to reduce immature bee populations. 21

Birds probably are the primary cause of high adult bee losses, particularly (luring emergence. Skunks and mice dig into bee sites, can consume large numbers of immature bees.-.21-22

2 by W. P. Stephen Assistant Entonwlo gist

The alkalibee, Nomia melanderiaverage for alfalfa seed produced per CkIL, is found from the Rocky Moun-acre was 181 pounds in 1956 and 179 tains and west, but abounds only in re-pounds in1957. Yields of 1,000 to stricted areas of each state. The spe-1,500 pounds per acre have been re- cies has been recorded inall of theported from several areas of North western states north of Mexico but ap-America. In the few areas of Oregon parently reaches large population den-and Washington where alkali bees are sities only in the northern half of themost abundant, yields of 1,200 pounds Great Basin. It has been found as farof clean seed per acre are not uncom- north as the Wenatchee area of Wash- mon. ington, but the limits of its range likely The alkali bee has been the principal include the southern parts of the in-contributor to the high seed yields re- terior valleys of British Columbia. ported in Utah (Bohart 1950)* and is Large numbers have been recordedthe main reason for better-than-aver- from many areas in the Great Basinage seed yields in the Yakima area of during the past 20 years. Their abun-Washington (Menke 1954) and South- dance in each case appears to haveern Idaho. In the past decade the high been associated with intensive alfalfaaverages of seed yield in Utah have de- seed production. The increase of al-clined steadily, as has the total acreage falfa seed production on a large scalein seed production. The causes of this basis in areas where the bee was nativedecline are many, but reflect primarily seems to have provided sufficient pol-the loss of the previous high popula- len for the bee to reach its peak intions of the bee through poor bee man- numbers. The combination of ampleagement practices and the haphazard or excessive food supplies associatedapplicationsofinsecticides(Bohart with adequatesites in which to nest1958). has resulted in production of enormous A knowledge of the habits and the local populations. Abundance ofthelife history of the alkali bee by seed bee in areas to which it is adapted ap-producers in areas to which the bee is pears to be limited solely by the avail-adapted is essential, for the future of ability of food, suitable soil conditionsthe alfalfa seed industry rests with the in which to nest, and the absence ofability to maintain or increase their frost during its flying period. numbers. The bee is one of the most effective The brief outline of the life history alfalfa pollinators, considering num- * Name and date in parentheses refer to bers and seasonal activity. The national literature citations, page 22.

3 and activities of the alkali bee that fol- 1955.It is possiblein fact, to be ex- lows is directly applicable to popula-pectedthat minor deviations from the tions studied in Oregon and the near-comments in this bulletin will be found by areas of Nevada, Idaho, and Wash-as more data are accumulated from ington. These studies were initiated in other regions.

4ie i4td Alkali bee nesting sites are foundyear for a variety of causes, many of mostly in silt-loam areas in which sub-which are still unknown. Bee studies irrigation by ground water has pro-in Oregon are continuing, with the ceeded for a varying number of years.hope of eventually stabilizing the bee Size of the nesting site and the amountpopulations and their nesting areas. of bee activity Ouctuate from year to

Emergence The bee overwinters as a prepupa, Observations made in both Malheur similar in shape and size to the larva.and Umatilla Counties indicatethat In the spring the prepupa transformsthe amount of soil moisture available to a "propupa" anft then to a whitein the spring also exerts a striking ef- early pupal stage (Figure 1). Afterfect on the beginning andrateof this, the pupa darkens. Wings, bodyemergence. Those beds in which the bands, and hair soon are evident. Beesamount ofsoilmoisture was above begin to emerge in a few clays after30%in June did not emerge until the tie pupa dlarkens. Rate of develop- moisture level had fallen to below25%. ment from the overwintering stage toOther beds located in better drained the adult depends primarily on soilareas had bees emerging three weeks moisture and soil temperature. earlier than the wetter beds. Even dur- Prepupae appear to have a restinging a single season, as in1958,the be- stage of several months, when theyginning of emergence in a single area cannot be induced to emerge even withwill vary by as much as three or four high temperatures. Once this period, weeks. called a diapause, has been satisfied, If the spring prior to emergence is transformation into a propupa and cle-extremely damp a great deal more heat velopment proceeds at a rate governedis required to raise the soil temperature by soil temperature. Laboratory studiesin the bee bed and emergence is de- reveal that the development and trans-layecl. Greenhouse studies on the effect formation from the overwintering pre-of soil moisture on emergence indicate pupa to the adult occur within nine that with a constant soil temperature of days when the prepupae are heldat80° F. in the level of the cells, emer- 90° F., to32days when the prepupaegence in a core of bees held above 20% are held at65° F.In these studies themoisture level proceeded much more temperature was the only factor varied.slowly than a core of bees held at6%. Temperature ranges from65° F.toAs most bee beds lie in naturally low 90° F.can be closely correlatedwith areas and are difficult to drain, partial the emergence rate. control of the soil moisture condition

4 can be obtained by supplying surfaceprepupa has begun, emergence will drainage to the site immediately aroundoccur within the next 14 to 25 days, the bee bed during the early part ofdepending upon the stage of develop- the spring. ment. If the pupae are black and their abdominal bands are evident, emer- Soil moisture indicates gence will be soon, although cool, damp emergence time weather may cause delay for several Soil moisture in natural sites pri-days. In 1956 and 1957 the bees began marily results from subirrigation. emerging late in June and did not reach Amount of rain and snow in alfalfaa peak until the middle of July. First seed areas during the early spring willcutting for hay would have been ad- indicate about when emergence can bevised during these years, since second anticipated. If the precipitation (luringgrowth would have reached full bloom March and April, for example, is highabout the time of peak bee emergence. or above normal, a late peak cmer-However, in1958 emergence began gence can be expected. If the precipi-(luring the last week of May, coming tation during these months is normalto peak about the middle of June. Cut- or below normal, as in 1958, an earlyting the first crop for hay under these emergence can be expected. conditions proved disastrous, for by Time of the emergence of alkali beesthe time alfalfa reachedfull bloom is important for the alfalfa seed pro-many bees had died and others had es- ducer. It determines whether first ortablished flight patterns to other fields. second cutting should be retained forWhen emergence occurs shortly after seed. Once development beyond thehay is cut, the benefit of the bees is

Figure 1.Stages in the development of the alkali bee. Upper left, egg on pollen ball. Upper right, mature prepupa. Lower left, early pupal stage. Lower right, adult female.

5 lost for most, if not all, of that season. some of the observation sites many of Peak emergence does not imply athe early females had died before the sudden appearance of great numberslater bees emerged. Table 1 indicates of bees. It indicates the date on whichthe gradually diminishing numbers of thetotal number of bees emergingalkali bees during August and early from caged plots was greatest. Follow-September, 1957, and July and August, ing the peak, the number of emerging1958. These counts were obtained by bees declines steadily. Thus, during afilling emergence holes in the evening cool, wet year, bees will continue toand recording how many had been emerge over a two-month period. Inopened by bees the following morning.

Table 1.New Entrance-exit Holes Cleared in Square Yard Plots

Site 1 Site 2 Site 1 Site 2 1957 Plot 1Plot 2Plot 1Plot 2 1958 Plot 1Plot 2Plot 1Plot 2

8/20 165 179 140 141 7/23 122 149 130 108

8/21 42 34 42 19 7/25 107 123 122 100

8/22 23 16 36 17 7/30 87 108 116 105

8/23 23 12 27 21 8/ 4 87 95 109 86

8/24 18 13 23 16 8/ 8 63 73 81 67

8/25 14 10 20 17 8/ 9 41 44 72 52

8/26 13 9 20 20 8/10 40 43 55 43

8/27 10 9 21 13 8/12 44 39 73 60

8/28 8 S 18 13 8/13 29 25 I 42 37

8/29 6 6 20 12 8/14 27 18 41 33

* * * * 8/30 8/15 21 16 24 I 27

8/31 5 5 17 7 8/16 19 14 25 19

9/ 1 3 5 14 5 8/17 16 14 23 17

9/ 2 2 4 11 5 8/19 12 8 19 18

9/ 3 2 3 9 5 8/20 12 9 15 13

9/ 4 2 3 7 5 8/22 5 3 10 I 9

9/ 5 2 3 8 3 8/23 4 3 10 8

9/ 6 2 3 5 2 8/25 4 3 7 3

8/26 2 2 6 2 * Rain washed out and covered holes.

6 Bee Populations Within Nesting Sites Number of prepupac per square foot prepupae will emerge, since there are of bee bedwill vary depending onmany and varied causes of mortality the population of adult bees workingduring the early spring. The average that bed during the previous season.emergence from one square foot of The populations of prepupae will varysoil in an excellent bee site will be well from bedto bed, and will even varyover 300 individuals. Half of these arc greatly within a single bed. Squaremales, yet each square foot of soil will foot samples taken from a number ofaccommodate about 50 tunnels at a max- beds in the Pacific Northwest indicateimum, and usually only 30 to 40. The that the number of prepupae per squareother bees from such a site must be foot will number as high as 468 in theaccommodated elsewhere and ifsuit- most populous bed, but even in thisable sites are not available they un- bed the numbers varied, some samples (lOUbtedlV perish. yielding only 40 to 45. Not all of these

Seasonal Emergence Males begin to emerge slightly be-use exit-entrance tunnels of a previous fore the females, but males continueseason. Apparently, however, they will to emerge throughout the season. use such emergence holes, if they dig The emergence of both males andinto them, in preference to digging females in the Pacific Northwest is re- their own; numbers of bees have been stricted primarily to midmorning hours.taken in emergence ti-aps from a urn- Occasionally, a few Specimens will be ted number of tunnels. Upon emer- noted as early as 8 am., but normallygence the bee is not immediately active the daily peak occurs between 9 :30 andbut rests near the nesting site for a 11 am. Few bees have been found tofew minutes before taking flight, flex- emerge in the afternoon. ing its wings and combing itself, giv- The bees emerge by digging outing the wings an opportunity to dry. through the soil and do not necessarily

Matings During this period of relative inac-tivity, they immediately seek a nectar tivity, mating occurs. Males hoveringsource. They return to the nesting site abovethesoilsurfaceduringthe(luring the afternoon of the day they morning imniecliately pounce upon andemerge and begin digging a nesting mate with any of a number of females.burrow by the middle of the same af- The females will take flight as SoOn asternoon. Males rarely, if ever, bother they are able. Those emerging in themated females actively engaged in con- morning take flightand if greenhousestructing nesting burrows. observations are indicative of field ac-

7 Nesting Females dig rapidly once they haveexisting clay hardpan. In a number of selectedsuitablesitesfor burrows.areas where thereisa shallow clay Within three to ten minutes they havehardpan at five inches, cells were all dug themselves under the surface. Evi-constructedabovethehardpan.In dence of their digging can be seen byother areas of the same bed where the the amount of loose dirt around tunnelharclpan ran deeper, nesting areas ex- entrances.Diggingapparentlypro-tended to the six-inch level. In some of gresses during the entire first evening.these areas which were highly popu- Mounds were removed from the tun-lated, nesting bands were found at the nel entrance in the late evening butsix- and ten-inch levels. new ones were there thefollowing A nest of the alkali bee consists of morning. By exposing several nestsa vertical tunnel of varying depth. In started the previous afternoon, it wasmost areas bee cells are constructed foundthat all of the bees hadpro-from five to seven inches below the gressecl to the five- or six-inch level bysoil surface. A vertical shaft of vary- the following morning and two hading contour leads from the soil surface begun excavation of the first cell. to the nesting sites. Figure 2 illustrates some ofthe forms of exit-entrance Beds built above hardpan tunnels bees construct. hi most beds a The depth to which the bees dig be-single layer of cellsis constructed at fore constructing the nesting layer ap-about the six-inch level. In areas where pears to depend on soil texture andthe bee population is extremely high, moisture as well as the level of anyand a suitable soil texture exists below

Fgure 2.Variations in construction of alkali bee exit-entrance tunnels. Note pollen balls and soil plugs in cells at tube ends. Typical nest is from 6 to 10 inches deep.

8 the six-inch level, often there will beand the appearance of the overwinter- two layers of brood. The second layering prepupa is about 10 to 12 days. may be constructed by later bes emer- Observations on the excavatedsoil ging from the same nesting- site or byat the surface of the exit-entrance tun- a single bee that has found its lateral nelsupport thefindingsofBohart expansion of the brood chamber re- (1955) that on each day during opti- stricted by the brood of other bees inmum weather conditions the bee lays the same area. Normally the verticalone egg, fills one cell with a pollen ball, exit-entrance chamber divergesjustand then excavates another to be filled above the brood chamber where a ser-the following (lay. These patterns ap- ies of two to five branch burrows leadpear to hold true throughout the life away. The structure ofthe verticalof the adult female. Bohart concludes shaft and of the number and form ofthat the pattern of preparing the pol- the branch burrows is nowhere con-len ball on one clay and laying an egg stant in appearance or depth. Where aon it the next was the rule during the second series of cellsis found belowthree weeks of his excavations on a the top level, invariably they are con- number of nests in Utah during 1952. structed after thefirstlevel of cells has been provisioned. A number of factors have been observed to inuence the rate of cell con- Cell build begins early struction by the female bee during the Cell construction normally begins onseason. These includetexture of the the second or thirdday after emer-soil, presence of a loose soil surface, gence. Each cell is excavated to formand the distance the bee must fly to the an oval cavity. The cells are then care- food source. Under ideal conditions the fully packed until the inside is smooth.bee will first lay an egg on a pollen The bee completes the cell excavationball that was furnished the previous by forming the sides and top of theclay, plug the cell after the egg is laid, oval, leaving a hole large enough forprovision a prepared cell with a pollen her to enter and leave. Once this hasball, and prepare a new cell for the fol- been done she lines the cell with a verylowing (lay. A single female does not thin film of clear waxy material whichcontinue this process for the four to is secreted through and applied by thesix weeks of her adult life, since each end of her tongue. The cell is then par-female is capable of laying only from tially filled with a pollen ball on which24 to 26 eggs. During a good season islaidalarge, banana-shaped egg.a single bee nest will contain an aver- (Figure 1). Following this the cell isage of 18 to 23 cells. Bohart reports a sealed by a soil plug and work pro-nest with as many as 24 cells with gresses on the next cell. brood but indicates the average in Utah After the egg is laid and the cell iswas from 15 to 20. sealed, there is an incubation period of two days,following which the egg Only one generation per year hatches and the larva begins to feed In thePacific Northwest there is and grow. The larva eats rapidly andonly a single generation of the bee per achieves full larval size by the end ofyear, but there is some evidence that a a week. It requires approximately three partial second generation does occur, niore days to change into the prepupa. particularlyin those years in which The total time between the egg layingbee emergence has been early. Several

9 clark pupae have been found latein were discovered within three days after the season in a nest constructed duringfinding- the (lark pupae. It is assumed that summer. These pupae undoubtedlythat these were second generation bees would have emerged that fall if left un-rather than late emergent first genera- disturbed. Several fresh burrows alsotion. Adult Habits Males ping the florets in the process of se- The alkali bee males have a singlecuring nectar. purpose--the fertilization of females. Females iViales are abundant, flying about the nesting- sites in the morning of each Once nesting has begun females en- day of emergence. During the after-gage solely in the collection of nectar noons and evenings they seek foodand pollen for the construction of pol- for their own survival and spend thelen balls in their brood chamber. They rest of the time in the fields, restingprefer alfalfa to most other wild and on flowers, under clods of dirt near thecultivated plants. There are some ex- nesting site, or under sticks, refuse, orceptions to this rule. Spearmint in the in furrows in the field. They never re-Yakima area appears tobe one of turn to the burrow from which theythem. Although great numbers of fe- emerged and apparently die in the field.males often can be found on sweet The males appeartoprefer sweetclover and onions, few, if any, have clover, corn, onion, and spearmint nec- been noted collecting pollen, and the tar over alfalfa and can commonly beexaminationof hundredsofpollen seen in numbers on these plants dur- balls in various nesting sites through- ing warm afternoons. In areas whereout Oregon reveals that alfalfa is the the above plants are scarce or absent,principal pollen source for these bees. males get their food from alfalfa, trip-In fact, no evidence of either onion or corn was seen in any of the pollen halls examined. Flight Range Females of a nesting area appear to Range of the adult bees away from workthenearestbloomingalfalfathe nesting site depends on several fac- available at their time of emergence.tors. Perhaps the greatest influence on When they have worked plants closesttheir range is the amount of alfalfa to the nesting site, the females expandavailable to the bee near the nest. If their range in increasingly larger cir-there are several hundred acres close cles. Often it appears that a new, pre-by, bees will have sufficient bloom to viously unworked alfalfa field has been work without extending more than a tripped "overnight," for the bees moveshort distance from the site. If the al- in large numbers and work rapidly. Itfalfa extends away from the nesting appears that they rarely, if ever, stop atsite along a restricted narrow area, the fields that come into bloom after theirbees appear to work two or three miles patterns have been established, evenbefore the season ends. Where alfalfa though these fields are closer to theis sparse and the acreage islimited, nesting Site. evidence indicates a large population of bees may extend four or five miles.fort must be made by seed producers The two last-mentioned situations areto have bee emergence peaks coincide rare. Usually thereis much more al-with available alfalfa blooms. falfa in a given area than there are bees Information available on the behav- to work it. ior of the alkali bee isstill fragmen- Adult females are relatively short-tary because of the difficulty in tracing lived, usually living not more than sixand observing marked bees in an area weeks in a good season. Thus every ef- populated with nesting sites.

1tedt.t9 £ae4-

Soil Texture and Moisture Major limitation to expansion of thenever above 8% and usually falls be- alkali bee is due to lack of availabletween 4% and 6%. In the poorer sites, nesting sites. Adult bees limit them-the amount of clay size particlesis selves to the selection of sites wherehigher,beds becoming progressively adequate soil moisture is obvious atpoorer with increasedclaycontent. the soil surface. This gives a compactAmount of clay size particles governs plane through which to burrow. Manythe rate at which the subsurface mois- times nests are noted where soil sur-tore can be transmitted by capillary ac- face is loose and fluffy, and the beestion to the soil surface. Transportation continue to work as long as the loose,of subsurface moisture to the soil sur- soft, topsoil does not restrict their ac-face is slowed by the increasing amount tivities. But even these sites normallyof clay. Evaporation from the soil sur- are firm and compact during the earlyface in these soils is greater than the summer, and it is merely the shortagerate at which the moisture can be re- of subsoil water during the latter partplenished. Thus, as thesoil surface of the season that causes the surface to dries,it becomes loose and powdery, become dry, loose, and poorly work-and bees spendthe greater part of able to the bee. their time attempting to keep the exit- Examination of over 70 bee bedsentrance tunnel free of soil that has during the past three years indicates fallen in. that soil moisture and soil texture de- termine the acceptability of a particu- Soil moisture must be maintained lar site. Only where subsoil moisture In soils with a low clay content but is high and the soil structure permits ithigh sand andsiltcontent, upward to rise to the surface is a site accepta-transportation of subsoil moisture by ble to the bee. capillary action is rapid, equaling or exceeding that of water loss through Mechanical soil analysis reported evaporation at the soil surface. Thus a Mechanical analyses of soils fromcompact surfaceismaintained and several excellent and several poor al-bees have continued free access to the kali bee beds are listed in Table 2. Inbrood. In soil that has either too much all of the excellent nesting sites thesand or clay, and where soil moisture percentage ofclaysizeparticlesisfluctuates greatly through a single sea-

11 Table 2.Soil Texture Analysis't of Alkali Bee Beds

Site No. Condition of bed Depth Sand Silt Clay Percent Perceni Percent Excellent, deep brood 0- 6" 31.50 62.20 6.30 6-12" 31.94 64.18 3.88

2 Excellent, deep brood 0- 6" 25.26 70.40 4.34 6-12" 26.33 70.60 3.07

3 Excellent, shallow brood 0- 6" 25.46 71.61 2.93 6-12" 23.53 58.38 18.09 4 Excellent, shallow brood 0- 6" 35.82 60.19 3.99 6-12" 29.90 56.00 14.10

5 Excellent, shallow brood 0- 6" 27.54 68.12 4.34 6-12" 21.96 61.76 16.28

6 Fair-Poor 0- 6" 27.24 61.18 11.58 6-12" 16.99 70.03 12.98

7 Poor 0- 6" 23.46 61.78 14.76 6-12" 31.09 56.89 12.02

8 Poor 0- 6" 33.91 53.88 12.21 6-12" 33.98 55.56 10.46 * Aggregate analysis following organic m-gter removal. son, larvae niay dry out when moisturenesting sites was recordedat weekly at the brood levelfalls below 10%.intervals throughout the season and is TvIany beds, which were started in whatcited in Table 3. In the spring, the appeared to be suitablesites duringmoisture level may be as high as 30% the early sutnmer, die out because ofto 35%,particularlyinseasonsin the shortage of soil moisture later inwhich a great deal of early precipita- the season. tion has occurred. By the time emer- Soil moisture in the natural beds isgence begins, moisture level drops to maintained by the underground move-20% to 25% and usually remains at ment of water and its accumulation in the 20% level in the good beds through- certain areas where the soil textureout the season. permits it to rise to the surface through Thus, the physical nature of the soil capillary action. Underground water with a texture as indicated above- may move great distances, continuallyplus a high salt content, appears to leaching out salts as it progresses, be-have a high water retention capacity fore it is able to reach the surface andand resists changes in soil moisture. form the moist alkali spots that areIf this high level of soil moisture is found in the arid regions of the Greatretained at the soil surface, bees appear Basin. to be able to establish and maintain Moisture in the excellent and poor them selves.

12 Soil Alkalinity The alkali bee is found in so-calledsoil texture and moisture conditions. 'black alkali" patches in the desert areaand in itselfis not a prime requisite of the Gi-eat Basin. The common namefor the establishment of new bee nest- of the insect has been derived from the ing sites. habit of establishing itself in such soil Alkalisoilhas beneficialqualities conditions. Alkalinity in itselfis notwhich help in maintaining moisture at essential to the maintenance of the bed the surface and throughout the vertical or attractiveness to the adult female.horizon. Alkali soil appears to have a Greenhouse experiments have showngreater water retention capacity than that the female will select any soil plotnonalkaline soils, and thus evaporation as long as the moisture is maintainedproceeds at a much slower rate. In ad- at a suitable level and the texture per- dition, through capillarity (the rise of mits her to work freely. Soil alkalinitywater from the lower soil levels to the is a secondary expression of suitableupper levels) there is a high accumula-

Table 3.Proportion of Moisture by Weight in Soil at Different Depths Depth Site and Condition Date 6 inches 12 inches 18 inches Percent Percent Percent Excellent, deep brood 6/27/57 22.09 23.62 2 1.30 7/ 5/57 24.67 29.94 7/ 5/57 24.86 33.04 7/ 5/57 26.96 25.18 7/10/57 22.56 26.27 26.70 7/15/5 7 25.23 32.29 30.69 7/24/57 27.46 30.85 26.44 7/29/57 25.62 29.78 27.77 8/ 6/57 26.84 30.82 31.01 8/15/5 7 25.39 32.62 32.69 8/21/57 20.24 25.80 31.81 8/29/57 20.43 27.57 30.01 Excellent, deep brood 7/24/57 25.49 30.06 30.94 7/29/57 27.55 30.78 30.76 8/ 6/57 23.23 30.87 32.65 8/15/5 7 24.72 28.49 27.73 8/21/57 22.70 25.62 24.55 8/2g/57 24.23 30.49 26.77 Good, deep brood 5/ 5/57 23.54 25.95 27.20 7/10/5 7 23.90 25.42 29.17 7/16/5 7 22.73 23.47 23.92 7/29/57 22.12 24.72 29.68 8/ 6/57 24.04 23.94 27.20 8/15/5 7 23.30 23.67 28.35 8/21/57 19.55 22.67 27.57 8/29/57 21.38 23.52 28.66 Poor 8/ 7/57 8.41 14.19 16.09

13 tionofsaltsatthesurface.Thissoluble salts. With the loss of mois- greater concentration of surface salttureit becomes extremely crusty or helps "pull" the water up from the sub-powdery. This loose surfacesoilis soil and keeps the soil surface moisthighly undesirable and very rarely, if and compact. An unconfirmed possi- ever, isvorkecl by the alkali bee. How- bility does exist that high salt concen-ever, the amount of sodium carried by trations at the surface absorb waterthe water is in excess of the total of from the air during the evenings andthe other salts mentioned, the soil sur- contribute to the maintenance of soilface becoming dense and compact. The moisture. excess of sodium leads to nearly an Alkali conditions of a soil are manyideal situation for the establishment of and varied. Great areas are termedthe alkali bee nest. Soils with this ex- 'white alkali'' and ''black alkali" soilcess of sodium are generally referred to types. "White alkali" has an excess ofas "black alkali."

Ground Cover There aredifferencesofopinion in the season prior to bee emergence. about the value of ground cover in beeBut thesoilsurface should not be nesting sites.If the nesting site ap-scraped unless the depth of suitable pears to be marginal and the amount of nesting soil texture is known. Several subsurface moistureislimited,itis excellent bedsin Oregon would be best to remove the vegetation throughruined if more than three inches of any one of several methods. Loss of soiltopsoil were removed. In these sites the moisture through plant transpiration ishardpan is shallow or the soil texture many times greater than the moisturechanges at about the seven-inch level. loss through soil surface evaporation.If the soil surface is sufficiently com- Small amounts fsparse growthpact, any commercial weed killer or rarely impede bee activity. However,soil sterilant can be used prior to bee in the counts made on over 40 excel-emergence. If the soil surface is loose lent nesting sites in the Pacific North-and has a tendency to powder, the use west, the population (as determined byof a sodium-base weed killer, such as the number of exit-entrance tunnelssodium chlorate is recommended. Ad- per squarefoot)was many timesdition of sodium to the surface tends greaterinthe vegetation-free areasto compact the soil surface particles. than in sites where ground cover cx-In sites having more than 20,000 parts isteci. If ground cover is not removedper million of salts, the addition of where it spreads over a good bee nest-sodium chloride in the form of fine ing site, there is danger that the colonyhay salt, and its watering-in has a sim- may not survive. ilar sterilizing- effect, since there is a Ground cover can be killed by alevel of salt above which even the most weeclicide or by shallow scraping earlysalt-tolerant plants cannot survive.

Reclamation Many bee nesting sites have beenor removing irrigation from afield lost because of changes in farm prac-near a nesting site which has served tices. Cutting in new drainage ditchesas a source of subirrigated water for

14 Figure 3.A method of reclaiming an area in which the subsoil moisture supply was insuficient. The proposed site has been scraped and shallow ditches bearing the necessary water have been placed at intervals through it. the bee bed are examples. In addition,isting subsoil water and maintaining a there are many areas in which soilsmoist upper soil. If the existing sub- of suitable texture occur but wheresoil moisture is very low the construc- there is insumcient soil water to keeption of auxiliary ditches spaced from the surface moist. It is possible to re-15 to 25 feet apart may be necessary claim or foster the establishment of(Figure 3). alkali bees in areas similar to those Care should be used when providing described above if water can be added.supplementary water. None should es- The success of such a program dependscape over the surface of the bee bed primarily upon whether a soilis of(luring the flight season. The bee bed suitable texture to transport water rap-can withstand large quantities of sur- idly in both lateral and vertical direc-face flooding during the fall and win- tions. ter months when the holes have been It is advisable to have the soil an-sealed, but very little summer surface alyzed for texture to be certain of themoisture can be tolerated. A sudden lowclayconcentration.Ifgroundsummer deluge of more than one-half cover is dense it should be removed byinch (luring an evening has eliminated shallow scraping or by the use of soilthe entire adult population of a bee sterilants. Shallow ditches--not morenesting site. Some protection against than 18 inches deepshould be dugaccidentalflooding can be given low around or above the proposed site andlyingbeebeds.Shallowdrainage filled with water. If the soil is of suit-ditches should be provided around the able texture, lateral and vertical waterbed or a slight slope to the soil sur- transportationcanproceedthrough face supplied. capillary action supplementing the cx-

15 Teeececede 4ei# Greatest cause of alkali bee loss has The alfalfa seed industry depends been the indiscriminate use of highlyupon cooperative efforts of growers toxic organic insecticides. The alkaliand an awareness of alkali bee habits bee, unlike the honey bee, cannot beand activities. Insecticides must be ap- moved out of areas when such chenii- pliedto alfalfa to control the destruc- cals are applied. The decline of the al-tive insects found on that crop. But falfa seed industry in Utah can be at-only those insecticides recoin in ended tributecl primarily to the improper useby the local County Agents should be of insecticides (Bohart, 1958). Care-used during the bioomng period. These lessness in the type of insecticide usedshould be apphcd only in thc late eve- on blooming alfalfa or drift of insecti-ning or early morning hours before cide over a bee site can all but elim- bees become active. Insecticides should inate the bee population within a clay.never be permitted to drift over nest- Unlike honey bees- -whose populations ing sites, and nesting sites should be can be rebuilt by the next seasontheclearly marked so applicators are aware alkali bees require more time tore- of their locations. Carelessness by a build. In several instances in easternsingle grower or applicatorislikely Oregon and Idaho, severely poisonedto cause serious consequences not only bee populations required four years toon the treated field but on the bees reach the population they had had priorworking the entire area. to poisoning.

eV44ed. The Bee Fly Heterostylum robustum (OS.) The principal parasite of the alkalilocated at its front. When the upper beeisa medium sizedfly,slightlyhalf of the pupa is above the soil, the larger than the bee itself. The adult flypupal skin splits along the midline and is a robust, fast flier with a yellow,the large, delicate fly emerges (Figure black, and white, hairy abdomen and a4). The fly begins to emerge from the long black Snout or sucking tube usedpupal stage approximately a week be- in feeding on nectar from blossomingfore the initial emergence of the alkali plants. Adults feed primarily on nec-bee, the date of emergence depending tar of alfalfa florets and are commonupon the environmental conditions of in fields near bee beds. Although at-that particular year. The flies continue tractive,itis most destructive to theto emerge during most of the period of natural populations of the alkali bee, bee emergence. reducing the population by as much as 90% in some areas. Fly, bees emerge at same time During the late spring the bee fly After emergence the flies rest on the changes to a pupa and pulls its way toground or hang from short vegetation, the surface by means of cui-ved spinespermitting their wings to dry so they

16 Figure 4. Stages in the development of the bee fly, H. robustum. Upper left, semimature larva of he bee fly sucking body juices from the prepupa of the alkali bee. Upper right, mature larva of the bee fly with the drained prepupa of the alkali bee. Lower left, pupal skin of the fly, showing slit along the back from which the adult has emerged. Lower right, adult bee fly female on stem of alkali weed shortly after emergence. may take flight. The daily emergencedornen. Their accuracy and discrimina- of flies corresponds closely to that oftion are poor, for many eggs miss thebee. New ernergents rarely arethe nesting tunnel or are deposited in found before 10 am, or after noon.crevices or on dark salt spots that re- During this interval of the day newsemble the alkali bee hole. The bee emergents can be easily noticed whereappearsto have no defense against parasitism is heavy. As many as 15 perthe fly and its egg-laying activity. The square yard have been recordedin anumber of eggs each female fly pro- single bed. duces is enormous. One female caught Fertilization by the males usuallyand dissected had over 400 mature eggs occurs after the females have begunin her ovary. An egg either falls (lown their flight. Copulating pairs have beenthe tunnelris carried down by the observed in the air or hanging fromactive female bee. Careful excavation plants. has revealed numbers of eggs in nooks The females begin their egg layingor curves of the tunnel. acti\'ity shortly after fertilization and are most prevalent over a bee site fromFly larvae sucks bee body juices 10 am, until 1 p.m. each day. Bee The fly egg hatches and the young, flies never light on a nesting site whileactive larva apparently seeks its way depositing eggs. They hover over thcinto a cell containing a prepupa. The soil surface and throw their eggs downparasite then embeds its mouthparts in the bee tunnel by a flick of the ab-the body wall of the immature bee

17 entlytheflylarvae,which beconie much less active as they mature, must find their host while still in the active stage.Itisdoubtfulwhetherthe plumper, rather inactive larvae can do much searching.

Fly survival low The fly survival percentage is relatively low. While it is claimed that the fly can totally eliminate a bed of alkali bees, these claims have not been confirmed by studies of this author. It appears only one bee prepupa isre- qLliredfortheflylarvato mature. However, itis possible that fly larvae may damage several bee prepupae on the way to the surface or may open one or more bee cells, permitting the entrance of fungus or bacterial disease which may eventually cause the Figure 5.A bee nestingsitewith two over- death of the prepupae. While the fly wintering flylarvaenear thesoilsurface and two levels of bee brood below them. larva actively destroys only a single bee larva, it may contribute to the death of several more.

(Figure 4), and begins sucking the Ground cover reduces parasite body fluids. The parasite continues to The number of parasites usually is grow as it ingests the bee contents andgreater in bee beds that are completely finally appears to reach maturity on afree of plant cover. Short, sparse al- single prepupa. The fly larvanowkali weed or a light grass cover usually rubbery. in skin texture and yellow-does not slow adult fly activity. Once brown in colormoves toward the soilthe ground cover is about four inches surface after it has reached maturity.high, however, rate of parasitism drops This is particularly true of those larvae sharply. These observations have led that mature early in the season. A fewsome growers to consider keeping some of the later maturing larvae will win-ground cover as a deterrent to bee at- ter in the original bee cell if caught bytack. Counts of bee burrows and counts lowfalltemperatures.Larvaethatof mature prepupae in thefall taken move toward the surface remain fromfrom weedy and clear areas of the same two and one-half to four inches belowbeds indicate that a heavy weed cover the soil surface where they spend theexerts an even greater restriction on winter (Figure 5). bee activity. Numbers of bees in a clean The young fly larvae feed only onbed is so many times greater than in a the fully developed prepupae of thepartially overgrown area of the same bee and have never been found in cellsbed that differences in rate of parasit- containing smaller bee larvae. Appar- ism are of little significance.

18 The Conopid Fly Zodion oblique fa.sciatum Macq. Another serious parasite is a conopid fly, small in size and with a pecul- jar!)' shaped abdomen (Figure 6). The fly has a unique habit of parasitizing only adult bees. The female is a rapid flier. She darts out at a passing alkali bee and quickly deposits an egg on the body. The exact mechanism by which the larva enters the abdomen of the bee is unconfirmed, but the larva reaches the interior of the abdomen and begins to mature by consuming the internal tissues. The fly larva continues to grow in the abdomen and during these early stages it does not appear to slow the basic activities of the bee. It soon takes its toll on the bee through sterilization by the prog- ressive starvation of the ovaries and theireventualdisplacement bythe steadily growing larva. During this period the parasitized Figure 7.Two pupae of the conopid fly. One bee continues to construct cells, collect specimen (above) has outer bee skin aroundit, as it appears in soil. Bee skin has been removed, pollen, and attempts to lay eggs on the exposing smooth brown pupae (below).

pollenballs. Eggs laid after the fly lai-va reaches half its normal size are nonfertile or so poorly nourished the)' are not able to hatch. Presence of many parasitic flies is indicated when a number of sealed cells in a bee bed contain pollen balls but lack developing larvae, especially when there is a series of such cells in the same nest. The weak- ened bee dies while in the nest before the fly larva matures. The mature larva occupies the entire interior of the ab- (lomen where it pupates. Man)' pupae can be observed (luring Figure 6.Adult female conopid fly.Note pe- the late fall or early spring in an in- culiar curved tipof abdomen.Flyis slightly fested bee site, with the pupa still en- more than half the size of alkali bee. closed by the abdominal skin of the bee

19 (Figure 7). Removal of the abdominal The conopid fly is not a serious pest segments exposes a smooth, brownin Oregon or western Idaho, but it has pupal case. The fly emerges from thebeen reported by Frick(1958)that pupal case during the period of beethe incidence of parasitismin some emergence the following spring andWashington beds is severe. Similar re- makes its way to the surface, where itports have been made by Bohart for mates and begins its parasitic job again.some sections of Utah.

Other Pests Several other species of insects areof the bee. The entrance to them is a parasites or predators on the alkali bee.uniform funnel shape so smaller in- In the Pacific Northwest they are notsects passing too close to the burrow as important as the bee fly or conopidwill fallinto the waiting jaws of the fly. larva. These burrows differ strikingly from Phorid Fly those of the bee, which either termi- A tiny fly belonging to the familynate flush with the soil surface or have Phoridae has been observed in severala mound of excavated soil at the sur- nests in Idaho and in three sitesin face. Observations in Oregon confirm Oregon. The phorid is smallaboutthe earlier reports of Frick(1957) the size of a large fruit fly. It may bethat the larvae or adults rarely attack overlookedwhennotabundant.Itthe alkali bee. The tiger beetle isa crawls down the exit-entrance tunnelpredator of minor importance in the and deposits an egg upon a pollen ballNorthwest and control usually is not before the cellis sealed. The egg of necessary. the phorid hatches shortly after itis laid. If the phorid larva reaches the Mites bee egg before hatching, it is capable of At leasttwo common speciesof destroying the egg. Bohart(1958) is mites are found in close association of the opinion, however, that the beewith the alkali bee larvae andrepupae. normally hatches first and in the pro-One, a small red mite appears to be a cess of consuming the pollen ball de-scavenger, feeding on the castoff larval stroys the fly larva. This species hasskins or on larval feca] material in the not been reported as a serious pest inbottom of the cell. Occasionally great any area where the alkali bee has been numbers of these mites will be noted studied. crawling about on the mature larvae and prepupae, particularly during late Tiger Beetles summer. Neither species of mites is Many tiger beetles often are seen inbelieved to be of any serious conse- bee nesting sites.Beetle larvalholes quence to the bee. Unless one species often are interspersed among the al-may possibly transmit a bacterial dis- kali bee burrows. These larval holes ofease from one larva to another, their the common species of tiger beetle inrole as parasites, predators, or disease the Northwest are smaller than thosetransmittors is minor.

20 &cte'i41 Dideaded

inallthenests observed inthe somewhere on the integument (outer Northwest there occurs a low degreeskin) followed by a rapid spread of of larval infestation by one or more the discoloration, eventually turning a unidentified bacterial species. Bacteria(larkchocolate brown.This widely cause the prepupa to discolor shortlyspread but relatively rare disease in the afteiit has reached this stage. Pre-Pacific Northwest is a minor cause of pupae first show a pale brownish spotmortality among immature alkali bees.

94i4e44e. Examination of many bee beds re-of prepupae have been taken in which veals varying intensities of infestation fungalgro\vth was foundemitting by the fungi, Aspergillus ustus and A. from an integumental rupture. Infected terreus, among the prepupae. For thebees appear to be healthy except for most part, the incidence of the disease thelocalappearance ofAspergilius islow, rarely exceeding 5% in any which soon spreads, eventually causing core sample. However, one bee bed lo- a total displacement of the prepupa by cated on the Oregon-Washington bor-a fungal ball. The fungus deteriorates der continued to have a high frequency (luring the winter, and by spring the of fungal disease among mature pre- lossis evident by empty cells and a pupae. Samples taken during 1957 and thin white film of mycelia and spores 1958 indicate that the rate of parasit-on the base and walls of the cell. The ism by the fungus is as high as 53%. fungus is common to all soils in much Neither of these species has been re- of western America but apparently acts corded previously as primary parasites,as a serious pathogen only in restricted but both have been noted as secondaryareas. Its general distribution through- parasites, entering weak, damaged, orout the soil makes it an extremely di- diseased organisms. However, numbers cult organism to control.

edato'd,

Birds Severe losses of the alkali bee haveinatelv selecting emerging and flying been attributed to blackbirds, English alkali bees, bee flies, tiger beetles, etc. sparrows, magpies, and meadowlarks Thereisadifference of opinion during emergence periods. Usually itabout the importance of bird damage. is easy to locate alkali bee nesting sites Undoubtedly birds can consume great during emergence merely by observingnumbers of bees in a short time, par- a concentration of bird activity on theticularly if the bird population is high. ground. The birds rest on the nesting But they also contribute to the control site and move about freely, indiscrim- of the bee fly by their general feeding

21 habits. The author believes that in Ore-during emergence of both the bees and gon and partsof Washington andthe flies, for itis at this period that Idaho adult losses attributable to birdsthe bees and flies are sluggish. It is are greater than the combined losseseasy for birds to pick up the insects at caused by all other insect parasites andthis stage; thousands can be rapidly predators. Yet, observations on severalconsumed. sites over the past four years indicate Magpies and blackbirds in particular that in spite of a high bird populationwill open or claw at a tunnel where during emergence, a moderately strongthe female is actively removing soil, bee colony was able to expand into aand many such females are extracted newly prepared adjacent area and com-by the birds. pletely populate the new site equal to The case against the birds has not the size of the old area. In other words,been proved but they definitely con- the size of the bed doubled in spite oftribute to a depletion of bees. The use the presence of many birds. The isola-of firecracker strings and bird traps tion of this bed from other known beehas helped reduce the high population beds ruled out the possibility of occu-of birds particularly during the emer- pation of the new area by bees fromgence period when they are most abun- another site. dant and destructive, but neitheris Bird populations always are greatest completely effective.

Skunks In restricted areas of the Northwest,eradicated sonic beds. skunks also present a serious problem. Various methods of excluding skunks They dig through the soil rapidly andhave been tried in Washington and expose the prepupae in the bed. Suchit appears that chicken wire screen or diggings are rewarding, for the pre-other wire screens of similar dimen- pupa population is high in better nest- sion mounted on 2'x2' or 2'x4' board ing sites, arid the animals are well fedframes and placed over the bed will re- for their work. In the Yakima andduce serious damage. Wapato areas,skunkshavealmost

Mice Mice,too, have damaged existingconsiderable losses. High mouse. popu- beds in Oregon and Idaho. Unless thelations such as those experienced dur- population is high, the damage usuallying the last two years in Oregon and is minor. During the past two years,Washington are unusual. Over an cx- the mouse population growth in thetended time the mouse probably is a Maiheur area of eastern Oregon hasminor limiting factor in the restriction been rapid, and certain beds sufferedof the alkali bee.

22 'ejewice4...

Bohart, G. E. 1950.The alkali bee iVoniia melanderi Ckll., a native pollinator of alfalfa. Report of 12th Alfalfa Improvement Conference, Lethbridge, Canada, Bohart, G. E.1958.Personal communication, Bohart, G. E. and Cross, E. A.1955.Time relationships in the nest construction and life cycle of the alkali bee. Annals of Entomological Society of Amer. 48: 403-406. Frick, K. E. 1957. Biology and control of tiger beetles in alkali bee nesting sites. Journal of Economic Entomology 50: 503-504. Prick, K. E.1958.Personal communication. Menke, H. F.1954.Insect pollination in relation to alfalfa seed production in Washington. Washington State College, Bulletin 555.