June, 1948 Mosquito News 61

STUDIES ON THE FLIGHT RANGE OF CERTAIN CULEX MOSQUITOES, USING A FLUORESCENT-DYE MARKER, WITH NOTES ON CULISETA AND ANOPHELES 1

W. C. REEVES, B. BROOKMAN, 2 and W. McD. HAMMON

George Williams Hooper Foundation, University of California, San Francisco

The problem of the flight range of of these and other related infections by Anopheles mosquitoes has been investi- the Hooper Foundation, Neurotropic gated rather extensively because of their Virus Research Unit. known relationship to malaria. These

studies have been well summarized re- Methods cently by Eyles. 1 However, few reports A review of the literature convinced us are to be found which concern the flight that none of the methods in common use range of the culicine mosquitoes, and we for marking, and later identifying the are acquainted with but one having to do same marked specimens among collections, 2 with Culex (Clarke ). Certain species was quite suited to our over-all fieid re- of Culex now are known to serve as search problem. If the large numbers of vectors of some of the important virus mosquitoes collected in the flight-range encephalitides of man and horse, in addi- studies could also be subjected to tests tion to their well-known role as carriers for the presence of viruses or to dissec- of human filariasis and the avian malarias. tion to determine sporozoite and oocyst Furthermore, their importance as pests rates in avian malaria surveys, we could cannot be minimized. accomplish more from the use of a limited With the increased appreciation of the group of trained field collectors. The use public health significance of Culex mos- of aniline dyes, commonly employed by quitoes and with the beginning in Cali- other investigators, required the moisten- fornia of extensive control programs di- ing of specimens with a solvent such as rected particularly against Culex tarsalis alcohol or acetone, thus rendering the Coquillett, it became necessary to acquire specimens useless for other studies. It was knowledge of the distances traveled by felt that the use of the alternative, metallic some of the commoner species of this dusts, would necessitate such elaborate genus in California. The studies herein precautions in preventing contamination reported were carried out during the sum- of clothing and laboratory equipment as mers of 1946 and in Kern County, 1947 to render field operations highly unwieldy. California, an area in which the Western It was also recognized that the type of equine and St. Louis types of encephalitis meticulous examination required for iden- are endemic. This same area has been tifying specimens so marked was very time a center for other epidemiological studies consuming. Therefore, a marker with the following characteristics was sought: 1 This investigation was carried out in collabo- ration with the Communicable Disease Center, (1) small amounts would be visible with- U.S.P.H.S..; and the Commission on Virus and out the use of a solvent; (2) it could be Rickettsial Diseases, Army Epidemiological Board, handled easily with a minimum chance of Office of the Surgeon General, U. S. Army, Wash- contamination of equipment, contact with ington, D. C; and under a contract with the California State Department of Public Health. which might contaminate unmarked mos- 2 Assigned to the George Williams Hooper quitoes; and (3) close microscopic exami- Foundation through the California State Depart- nation of individual specimens would not ment of Public Health by the Communicable Dis- be required for its detection. The fluores- ease Center, U.S.P.H.S. cent dyes seemed best to fit the above Read at 1947 Annual meeting of the American Society of Tropical Medicine. characteristics. 62 Mosquito News Vol. 8, No. 2

Beginning in San Francisco in May 1945 irradiated with the dark light, a brilliant the following dyes were tested: * rhoda- red fluorescence was observed. The temale mine, anthracene, fluorescein, uranium mosquito retained this fluorescence for salts, uranin, riboflavine and fluorescent at least 7 days in the laboratory, even purple. Before the findings of these labo- following a blood meal and the subse- ratory studies could be applied to field quent formation of eggs. It also has 3 tests, Zukel reported tne findings of been noted that the dye is still visible

laboratory studies of a somewhat similar after death of the mosquito for at least 4 nature. Following this Chang published 19 days. Although in field tests, several a report on laboratory studies of fluores- recoveries were made of mosquitoes which

cent materials as markers for mosquitoes. had fed thus on the dye solution, this

However, the above authors did not point method is not too well suited to flight out that fluorescent particles frequently range studies, principally because of the are to be found on field-caught mosquitoes, difficulty in getting a large proportion of and occasionally even on laboratory-reared specimens to feed on the solution. How- specimens. In examinations under ultra- ever, it would appear that this method violet radiation of over 78,0:0 freshly killed does offer certain advantages for use in field-collected mosquitoes in Kern County, tagging mosquitoes for other biological numerous specimens have been observed studies, since there is a minimal chance to have minute fluorescent blue, purple, of damaging specimens or of contaminat- green, white, yellow or orange particles ing unmarked ones. on their bodies. However, we did not The application of fluorescent dyes to observe on these mosquitoes any naturally the bodies of mosquitoes as dusts has been occurring red-fluorescent materials. There- found to be the method of choice. Zukefs 8 fore, rhodamine-B (National Aniline Divi- method of preparing and applying the sion, Allied Chemical and Dye Corpora- fluorescent materials was used. Briefly, tion), a water-soluble dye producing red this consists of mixing one part of the fluorescence under ultra-violet light was dye with 6 parts of gum arabic, adding finally selected for use in all of the field water until the mixture is of a pasty studies herein reported. consistency, allowing this to dry, and then In the laboratory, attempts to obtain grinding it to a fine powder in a mortar. adequately marked adults from larvae The powder is applied to adult mos- reared in 1:1,000 to 1:10,000 solutions of quitoes in the holding cage, by means of rhodamine-B in water were unsuccessful, a hand-operated powder blower (DeVil- either because of high mortality among biss, #118), after which the humidity in larvae or of failure of the dye to carry the cage is raised nearly to saturation. The over into the adult stage. Similar unsatis- dye-gum arabic particles, absorbing mois- 4 factory results were reported by Chang. ture, adhere readily to the mosquitoes' It was found, however, that 25 to 50% bodies, and apparently are not lost after of adults feed readily on 1:1,000 to drying. The minimum amount of dust 1:10,000 solutions of rhodamine-B in necessary to clearly mark the mosquitoes sugar water. No toxic effects were noted should be used. An excess will result in on comparison with controls fed on sugar increased mortality and decrease in flight water alone. Adults which had fed on power. To determine the proper amount such a solution retained a characteristic requires some preliminary experience. carmine-red coloration of the abdomen All mosquitoes used in the flight-range readily visible in ordinary light. When experiments were reared in the laboratory from field-collected larvae and pupae. Dur-

51 We are greatly indebted to Dr. Louis A. ing the first year's study, adults, as they Strait, of the University of California Medical emerged, were transferred by means of Center, for valuable advice and assistance in select- a sucking tube from the emergence ing these dyes and a proper source of ultra violet cages light of suitable wave length. to a wooden, screen-topped, holding and June, 1948 Mosquito News 63

release cage. At this time they were ing in the water at this time were counted counted. Since pure cultures of any one to determine the actual number of adults species of mosquitoes ordinarily were not emerged. Following this, the rhodamine-B available, a sample of adults from the gum arabic dust was introduced in the emergence cages was identified. By this same manner as previously described arid means the approximate number of each wet towels were placed over the top of species was estimated. During the entire the can to maintain a high humidity. holding period the adults were offered Then, the cans were transported from the solutions of rhodamine-B in sugar water laboratory to the release point, a distance on cotton pads. Within 48 hours after of about 20 miles. After release all adults emergence, the adults were transported remaining in the cans were identified, to the point of release in the holding cage, counted and checked for presence of the which was wrapped in wet burlap sacks fluorescent marker. in order to maintain a humid atmosphere. The center of the experimental area

In spite of all precautions, however, it was selected as the release point. was found that the mortality of mosquitoes For recoveries mosquities were collected in the holding cage was about 25%. Ten from preselected stations by means of suck minutes before release the mosqukoss were ing tubes. Those from each collecting sta- dusted with the gum arabic-dye particles. tion were placed in separate small carrying Several modifications were made in the cages. As far as possible, collections were procedure for the second year's studies. made in all directions from the release Larval and pupal stages of mosquitoes, point at distances varying from 0.2 miles principally of the species Culex tarsalis up to 3 miles. Upon return to the labora- but including small numbers of Culiseta tory the mosquitoes were lightly chloro- mcidens Thomson and Anopheles pseudo- formed, and examined immediately in a punctipennis franciscanus MacCracken dark-room under a low power dissecting were collected simultaneously in a prolific microscope for the presence of rhodamine breeding area. The proportion of each particles. For a source of ultra violet species was determined by the identifica- light an H4 Mercury lamp (Keese Engi- tion of samples of larvae and adults from neering Company, Shannon No. 92-LS) the cultures. These were held in the equipped with two Corning heat resisting laboratory in white enamel pans. As the glass filters, a blue and a red-purple, was pupae appeared they were transferred in used. This lamp produced light with an accurately counted lots of approximately average wave length of 3400 A and a 500 into 50-pound shortening cans which range of 3100 to 4000 A. Detailed exami- had been modified by replacing the centers nation and handling of individual speci- of the covers with bobbinet and by brazing mens was not necessary. The rhodamine short copper tubes into the bases of the particles adhering to marked mosquitoes cans as water outlets (Fig. 1). Adults were readily visible as brilliant red pin were permitted to emerge in these cans points of light. Marked specimens were and were offered a solution of rhoda- separated and identified. Using this tech- mine-B and sugar as food. Specimens nique it was possible to examine over were held in the cans for from 3 to 7 1,000 specimens per hour. The short days before release. It was found that the period of exposure to this intensity and mortality in pupae and adults amounted wave length of ultra violet apparently doe? to less than 5%, probably because of the not inactivate virus in the mosquitoes for relatively small numbers of insects for the numerous virus isolations were made in available space and also because a high both 1946 and 1947 from mosquitoes humidity was maintained. In preparing which had been examined for fluorescence for the release of the mosquitoes, the water in flight range studies. in the bottom of the rearing cans was The 28 square-mile experimental area drained. The dead or live pupae remain- is level and consists of farmyards and 64 Mosquito News Vol. 8, No. 2

cultivated fields. No communities are in- female at 1 mile from the release point. cluded in the area. The principal crops are Of approximately 26,700 Culex quinque- cotton, potatoes, tomatoes, alfalfa, cereals jasciatus released and 18,244 specimens and deciduous fruits, chiefly peaches. All collected, 58 marked specimens were re- crops are constantly irrigated during the covered. The distances at which recap- summer months, and normally there are tures were made are summarized in present large numbers of the mosquito Table 2. Twenty females and 27 males species included in this study. The area is characterized by high summer tempera- Table 2. Summary of Recoveries of Marked tures and low relative humidities. During Culex qiunquejascuitui, 1946 the time of these studies daily maximum temperature ranged from 81 to 105 F. Distance in miles Females Males and relative humidity ranged from 8-73% from release point recovered recovered with the mean below 40%. The entire area had been carefully 0.2 20 27 0.5 mapped during preceding years for other "•75 2 studies, and complete records of the distri- 1 .0 3 2 bution of buildings were available. Also, 2-5 1 the preferred adult mosquito resting places Totals 28 30 were well known. The collection stations were determined by the occurrence of pre- ferred resting places for adult Culex. All were recovered at 0.2 mile, 2 females and stations were man-made shelters, such as: 1 male at 0.5 mile, and the maximum porches, chicken houses, pump houses, distance at which a recovery was made out-door privies and garages. was 1 female at 2.5 miles. Although detailed records of direction 1946 Study and Results and intensity of air movement are not From May 20 to June 28, 1946, five available for the period during which releases were made totaling approximately the studies were made, it was noted at 47,700 mosquitoes belonging to the species the release point that in the early evening Culex tarsahs, Culex stigmatosoma Dyar there was usually a light to heavy north- and Culex quinquefasciatus Say, with ap- west breeze which died down by 10:00 proximately equal ratios of males to p.m. United States Weather Bureau re- females. These releases were all made ports from Bakersfield, about 20 miles between the hours of 5 and 7 p.m. Be- south of the study area, recorded a pre- tween May 21 and July 2, collections vailing air movement from the northwest were made on 13 days in an attempt to with daily maximum velocities ranging recover marked specimens. The distances from 13 to 31 miles per hour during the at which all recaptures were made are study period. The two releases of Culex summarized in Table 1. quinquefasciatus were made on relatively

A total of 11,800 marked Culex tarsalis quiet evenings. Two releases of Culex tar- were released. Of* 14,873 specimens of this salis and Culex stigmatosoma were made species collected after the releases only on evenings when a strong northwest 5 marked females were recaptured. Two breeze was blowing; the third was made of these were taken at a distance of quiet on a evening. Only 13 of the 73 0.5 mile and 3 at 0.2 mile from the point recoveries were made to the north or west of release (Fig. 2). of the release point. The greatest distance About 7,500 marked Culex stigmato- at which recoveries were made in the soma were released, and 3,048 specimens direction against the prevailing wind were of this species collected subsequently. Ten as follows: C. quinquefasciatus, 2 females marked specimens were recaptured: 6 at 1 mile and 2 males at 54 mile; C. tarsalis, females and 3 males at 0.2 mile, and 1 2 females at 54 mile. 1

June, 1948 Mosquito News 65

Table i. Summary f Marked Mosquitoes Released and Specimens Recovered in 1946

Total No. Marked Specimens Coll jctecl Approx. Date of Mos- Date of Species No. of Col- quitoes Distance Release Released Released lection Collected Species Number Travelled

5--21 432 C. tarsalis 1 . 2 mi.

1 C. stigmatosoma . 2 mi.

5-22 584 C. stigmatosoma 2

tarsalis 5-20 C. 2,800 5-23 274 C. stigmatosoma 1 0.2 mi.

C. stigmatosoma 5,800 C. stigmatosoma 1 1.0 mi.

5-24 943 C. stigmatosoma 1 0.2 mi. C. tarsalis 1 0.5 mi.

5-28 8.5 C. tarsalis 1 , 2 rni.

C. stigmatosoma 4 . 2 mi. C. tarsalis 1 0.5 mi.

6~i 1 C. tarsalis

C. stigmatosoma 3,400 6-12 1,976 C. quinquefasciatus 1 0.2 mi. C. quinquefasciatus 1,200 C. quinquefasciatus 1 1 , mi.

C. quinquefasciatus 6 , 2 mi. 6-13 C. quinquefasciatus 6,500 6-14 C. quinquefasciatus 1 . 2 rni.

C. quinquefasciatus 1 . 5 mi.

6-18 3.964 C. quinquefasciatus 1 0.2 mi. C. quinquefasciatus 6 0.2 mi. C. quinquefasciatus 3 1 . im, C. quinquefasciatus 1 . mi. C. quinquefasciatus 1 0.5 mi.

C. quinquefasciatus . 1 0.75 mi. 6-18 C. quinquefasciatus 19,000 C. quinquefasciatus 1 . 5 mi.

6-19 4,165 C. quinquefasciatus 11 0.2 mi.

C. quinquefasciatus 1 1 . mi.

C. quinquefasciatus 1 2.5 mi.

6-20 5.968 C. quinquefasciatus 9 0,2 mi. C. quinquefasciatus 2 0.2 mi.

6-29 2,490 C. tarsalis 1 0.2 mi.

6-28 C. tarsalis 9,000 7-i 5,616 no recoveries

7-2 3.719 no recoveries

1947 Study and Results Table 3. Number of Mosquitoes Released in Each Week of the 1947 Study This study was conducted between June 15 and July 23, 1947. During this period Week Total Specimens Released a total of 23,021 mosquitoes consisting of * 93.6% Culex tarsalis, 4.5% Anopheles June 15-21 3. 6n 22-28 pseudopunctipennis jranciscanus and 1.9% June 4.522 June 29-July 5 4.675 Culiseta incidens were released on 8 dif- * July 6-12 6,251 ferent occasions (Table 3). Approxi- July 13-19 3,962 mately equal ratios of males and females Total 23,021 of each species were included in the re- leases. Collections were made on each of * Two releases made this week. 66 Mosquito News Vol. 8, No. 2

26 days, and a total of 42,783 mosquitoes were partially engorged and gravid, and of all species were collected in an attempt 2 were freshly engorged. to recover marked specimens. Thirty-two marked mosquitoes were recovered. These Discussion and Interpretation of Data

included 18 female and 10 male C. tarsails In these studies it soon became obvious

(Table 4 and Fig. 1), 2 female and 1 male that the number of marked specimens re-

Table 4 . Summary of Mosquito Collections Made in 1947 for Rcco\ ery of Marked Specimens: Results for Culex tarsalis Onh

No. C. tarsalis No. marked C. N ->. mosquitoes collected tarsalis recovered Study No. No. collect- No. collec- all species A f Ring sq. mi. ing stations tions made collected F M Total F M Total

o-Vi mi. .8 32 2623 667 2 55 922 7 6 13

Vi—j mi. 34 lb 126 13906 900 3216 9 3 12

1-1 Vi mi. j-9 2(15 17183 1868 540 2408 1 1 2

1 14-2 mi. 5-5 9 40 2255 137 21 158

2-3 mi. 15-7 6 64 7042 923 133 1056 1 << 1

Total 28.3 59 467 43009 59" 1849 7660 18 1U 23

A. pseudopunctipennis, and 1 male Culi- leased represented but a very small part seta incident. The maximum range at of the relatively enormous mosquito popu- which these species were recovered was: lation naturally present in the 28 square C. tarsalis female 2.5 miles, male 1.1 miles; miles of the study area, and that with the A. pseudopunctipennis female 0.9 mile, personnel available and territory to be cov- male 0.9 mile; and C. ineidens male 0.6 ered, the number of recoveries would be mile. relatively small. In 1946, of approximately As in 1946 detailed records of direction 47,000 marked mosquitoes released, only and intensity of air movements are not 73 were recovered, or less than one out available for the study area. United States of 650 released; and in 1947 only one mos- Weather Bureau reports from Bakersfield quito was recovered out of 720 released. recorded a prevailing northwest wind dur- In Table 5 the collection data for 1947 ing the study period with daily maximum have been presented on the basis of samples velocities ranging from 12 to 29 miles per hour. Of the 8 releases two were made

on quiet evenings, 3 during gusty inter- mittent breezes, 2 during strong breezes, and for one, observations regarding the wind were not recorded. The majority of the recoveries of marked Culex tarsalis (22 of 28) were made to the north or west of the release point (Fig. 1). The opposite was true in 1946 when only a small proportion of all re- coveries (13 of 73) were made upwind. It is interesting to note that 7 of 18 Culex tarsalis females recovered had suc- ceeded in obtaining a blood meal subse- quent to their release; 3 were gravid, 2 Fig. 1. Mosquito rearing cans used in 1947 study 1

June, 1948 Mosquito News 67

Table 5. Average Collection Figures per Square Mile of Study Area 1947

Average No. Average No. Recoveries Average No. Average No. moscjuitoes C. tarsalis collected marked

Study No. stations collections collected C. tarsali? Ring sq. mi. per sq. mi per sq. mi. per sq. mi. F M Total sq. mi

mi. 0.8 o-Vi 7-5 40.0 3279 834 33i 1 1 65 16.25

54-i mi. 2.4 7o 52-5 5794 965 375 1340 5.0

1-1 Yi mi. 3-9 5.6 52.6 4406 479 138 617 0.50

1 V1-2 mi. 5^5 1.6 7-3 410 25 4 29 0.0

2-3 mi. '5-7 0.4 4.1 59 9 68 0.06

Total 28.3 2. 16.5 1520 209 65 271 0.99

and recoveries per square mile of study point. However, even with limited sam- area. The authors do not feel that these pling beyond one mile, one recovery- data should be submitted to extensive each of Culex tarsalis and Culex quinque- statistical analysis. The numbers of re- fascicttus was made at 2% miles distance coveries made were too small to suggest from the release point. We cannot say their use for derivation of estimates of that these species will not travel longer the natural mosquito populations in the distances. It can be seen even from these experimental area as was carried out by relatively limited studies that an extensive Eyles and Cox with Anopheles quadri- breeding ground of C. tarsalis, C. quinque- maculatus Say; or analysis of flight distri- fasciatus and possibly C. stigmatosoma bution patterns as was carried out by although located a mile or more outside 6 Pvussell et al. with Anopheles culicijacies of the boundaries of a mosquito control 7 Giles; Gilmour et al. with blowflies ; or district or municipality could serve as an 8 Jackson with tsetse flies. The above important source of infestation. Thus we authors found large standard errors in can not consider infestations with these their data and encountered many difficul- species solely as a backyard or neighbor- ties in interpretation even though their hood problem with regard to either their numbers of specimens released, and num- pest or disease vector activity. As a result bers recovered were much larger than of the findings of this survey, although those in the present study; and their the data are admittedly inadequate, we* methods of sampling were much better feel that as a tentative practical limit for standardized than was possible in the control measures they should be carried present study. out in a zone not less than one and one- The present studies were not designed half miles beyond the human or equine to determine maximum range of flight, hosts to be protected. It could very well but rather were designed to estimate what be that under different conditions of tem- 6 Russell et a/. have termed "the effective perature, humidity, wind or topography flight range." * The bulk of the recoveries this species would have a longer life or an were made within a mile of the release inclination to travel longer distances. If

this is demonstrated by future studies the above recommendations will have * The effective flight range of a species being to be the maximum distance from its breeding places revised. that a species normally is able to fly in effective The fact that recoveries of Anopheles numbers. By effective numbers these authors pseudopunctipennis jranciscanus, and Cult- meant in numbers sufficient to propagate a mos- seta inadens were to quito borne disease or to constitute a mosquito made up 0.9 and nuisance. 0.6 mile respectively means that these 68 Mosquito News Vol. 8, No. 2

species will travel at least that far, and it of a dust, or as a solution in sugar water may be that they will travel further. The by feeding has definite advantages under information obtained on these was inci- some circumstances over liquid dyes used dental to the main study, and they were as sprays, or over metallic dusts. However,

included only because of the impractica- it must be emphasized that in certain areas bility of separating the immature stages at least, naturally occurring fluorescent from those of C. tarsalis at the time of materials may be found in or on mos- rearing for marking and release. quitoes. Such fluorescence may lead to The new technique of marking mos- false results and confusion unless the dye

quitoes with a fluorescent dye in the form selected for use in an experiment is distinc- DISTRIBUTION OF COLLECTING STATIONS AND RECOVERIES OF CULEX TARSALIS IN 1146-1<34T PREVAILING WIND

X Release point. • Collecting station O Number females recoveped 1WT A Number- males recovered l^T G3 Numbe-P females recovered. 1^46 June, 1948 Mosquito News 69

tive in color. Thus, a large series of nor- a half miles from any population it is mal field-collected mosquitoes from any necessary to protect. study area must be examined prior to selection of the dye, in order to rule out Acknowledgment the possibility of a naturally occurring We are especially indebted to Mr. A. F. fluorescent material being mistaken for the Geib, Manager of the Dr. Morris Mosquito dye used. Abatement District, and the personnel of Summary this organization for the extensive coopera- The fluorescent dye rhodamine-B has tion and assistance given in this study. been proven satisfactory for the marking of mosquitoes in flight range studies. Use References

this its of dye and recognition by ultra 1. Eyles, D. E., A critical review of the litera- violet light after recapture leaves the ture relating to the flight and dispersion specimens in suitable condition for other habits of anophelme mosquitoes. U. S. Public Health Service, Public Health Bull. studies, including virus isolation or dissec- No. 287, 1944. tion for Plasmodia. Details are given of 2. Clarke, J. L., Flight range and longevity of the methods of applying and recognizing mosquitoes dusted with aniline dye. Proc. 30th the dye found most satisfactory for field Ann. Meeting, New Jersey Mosq. Exterm. Assn. 227-235, 1943. studies. pp. 3. Zukel, J. W., Marking Anopheles mosquitoes In Culex quinquefasciatus, 1946 Culex with fluorescent compounds. Science, W2: tarsalis and Culex stigmatosoma were 157. 1945. demonstrated to have a flight range of 4. Chang, H. T., Studies on the use of fluores- cent dyes for marking Anopheles quadri- at least 2.5, 0.5 and 1.0 miles respectively. maculatus Say. Mosquito News, 6:122- In studies, observation of the 1947 125, 1946. flight range for Culex tarsalis was extended 5. Eyles, D. E., and Cox, W. W., The measure- to 2.5 miles, and Culiseta incident and ment of a population of Anopheles qtiadri- maculatus Say. Natl. Mai. Soc, 2:71-83, Anopheles pseudopunctipennis francis- J. 1943. canus were found at distances of 0.6, and 6. Rdssell, P. R, Knipe, F. W., Rao, T. R., and 0.9 mile respectively from the release point. Putnam, P., Some experiments on flight range culicifacies, It is concluded that in Kern County, of Anopheles ]. Exp, Zoo., 97:135-163, California, under the conditions of these 1944. 7. Gilmouk, D., Waterhouse, D. F., and experiments the effective flight range of McIntyre, G. A., An account of experi- Culex tarsalis, Culex quinquefasciatus and ments undertaken to determine the natural possibly Culex stigmatosoma is at least 1 population density of the sheep blowfly. mile, For protection against disease bear- Council Sci. and Ind. Res., Commonwealth Australia, Bull. No. 195, 1-39, 1946. ing or pest activities of these three species, 8. Jackson, C. H. N., On the true density of mosquito control activities should be car- tsetse flies. J. Anim. EcoL, 2:204-209, ried out for a radius of at least one and 1933^

KING HONORS DR. BISHOPP

Dr. F. C. Bishopp of our Bureau of who will hold it until Dr. Bishopp can

Entomology and Plant Quarantine was legally receive it. Because of material recently awarded His British Majesty's shortage in the United Kingdom, it will Medal for Service in the Cause of Free- be some months before , the insignia be- dom, in recognition of his valuable services comes available, but the ribbon will be to the Allied war effort in various fields sent the Department of State in the near of scientific research and development. future. This is a signal honor for a Lord Inverchapel, the British Ambassador, worker.™(From Vol. 8, No. 6. of conveyed his personal congratulations as USDA well. The decoration will be tendered the USDA, a government publication for Chief of Protocol, Department of State, Agriculture employees.)