Daniel K. Miller JY84 -

SIMON FRIGER IJN I'JEKSTTY

A11 rights reserved. 7h-is thesis inay not be reproduced in whole or in part, by photocopy or other means, without pet-lnizs'iqn of thc ;~tithor. Approval

Name : Daniel R. Miller

Degree : Master of Pest Management

Title of The life-history and biology of the bark , Professional Paper Ips latidens (LeConte) (Co1eoptera:~colytidae)

Examining Committee

Chairman: Dr. L. D. Druehl

Dr. ~&nH. Borden, senlor supervisor

UL. A. T. Beckenbach

-- n, Associate Professor, r'aculty estry, University of British Columbia, Public Examiner

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I hereby grant to Simon Fraser University the right to lend my thesis, project or extended essay (the title of which is shown below) to users of the Simon Fraser University L i brary, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. I further agree that permission for multiple copying of this work for scholarly purposes may be granted by me or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without my written permission.

The life-history and biology of the , -Ips latidens (LeConte!

(Col eoptera :Scolytidae) .

Author: (signature)

(name

(date) iii

The I ife-history and biology of --Ips .--latidens -- (LeConte) were investigated using bark-sandwich and whole-log rearing ~ethods. In contrast to other .- Ips spy., some fen~alesinitiated gai 1 eri es under female-biased sex ratio conditions, and sometimes 2 ou. more ma1 as Here present in a gal 1 ery. In general , however, I. .. laticlens.-.- exhj bited

and achieved a mean fecundity uf 54.4 eggs. The larvai stage conipriscd 1 807, of the generation ,lime (egg to tenera7 adult) and the diskribution of headcapsul e widths di~closcd 3 larval ins tars. The muan ~tirvivor- ship within brouds wds 56.02 after 70 days; the reprvductive success

Singl c

hence, hartrrri

4l 1.tit - iiu~ili~tlOC DEDICATION

To those who study biology, and dLl.empt to (1 issolve tr:~~nyth-rrc~ i distinction betideen pure and appl I ed researc!?, ACKNOWLEDGEMENTS-

I am very grateful to Dr. J.H. Borden for his continual support and encouragement during the course of this research, and his guidance in my professional training. Drs. A.T. Beckenbach, L.M. Dill, J.A. McLean and

B.D. Roitberg offerred constructive criticisms of my manuscript. Dr. D.E.

Bright, Jr., Biosystematics Research Institute, verified my identification of Qs -. --:at-idens and --I. pin-i. Mr. F.G. Long provided expertise in photography and is credited with the frontispiece of -I. -latidens and Fig, 1.

I thank I. Borden, T. Ebata, D.W.A. Hunt, and particularly L.J. Chong, for their field and laboratory assistance. During my studies I received financial support from the H.R. MacMillan Family Fund and research support from NSERC Operating Grant A- 3881 to Dr. J.H. Borden. TABLE OF CONTENTS

Page

Exa1n.i niny Co~~in~-itteeApproval ...... ii Abstract ...... ii i Dedication ...... iv ~cknowiedgernents ...... v

Table of Contents ...... fs...... l.,l-*r.. v i

List of 'Tables v -I ii

List of Figures ...... j ,.

.-.-.-.. .-.-.-.. 1 NTROOUCllON ...... ll..*I.*...... OP..A.SS..L.l

..-----MM'ERlilLS AND METtiOOS ...... COLLECTION OF AND HOST MATERIAL ...... REARING METHODS ...... Colonies ......

-----Pi1 l -c*su'l e technique ......

Bark-sandwich------technique ...... SkX Dl FFtRENTSI\TION ......

REARING EXPERIMENTS .7.s...... l..LI.

-Brood survivorship ...... RESULTS AN11 DISCUSSION --.- --,-.. - ...... SEX DIFFERENTIATTON ......

GALLERY CHARACTERISTICS AND KEIiAV JOR ...... RE~UI-TSAND DISCUSSION icont . ) __CX-II--C------DEVELOPMtN T ...... 26

----Number of larval --.--instars ...... 26

---Durdtion of I i Fe stages.- ...... 2 6 Brood survivorshii ...... 30 EMERGENCE PATTERNS ...... 3 5

--.--Sex ratio ...... I...... s.. 3 5 Annual fl ipt periods *...... *...... 3 5 -.. -p ..... Emergence synchrony ...... 3 6

IMPLICATIONS TO FOREST PEST MANAGEMENT ...... 3 Y

---.----LlTERATURE CITED ...... 4 1 Page

Accuracy in differentiating the sexes of the basis of secondary sexual characters declivity...... 1I

Mean number of eqq tunnels constructed w thin 65 separate 1~ itidens monogarnous -- --I gal eries in ---Pinus --. contorta var. -latifo? la...... 2 3 Mean headcapsul e widths of 7 Q (n=749). ..a..aa,s..--. h. 4 Figure Page

1. Plexiglass-styrofoam bark sandwiches...... 6 2. Copulatory position of I. latidens in -P, ---contorta var. lati fol- ia bark sandwich%, ...... 3.5 3-4. Rate of niche construction and oviposition by ips in P, contorta var. latifolia at 25-35 'c. Fig. 3, I, 1atiJens. p-. ..------.-- -- Fig. 4, -I. ~"in?...... 18 5-7. Spac-ing of niches in egg tunnels by female ips at 25-35 'c. Fig. 5, -I, .---pin1 in P. ----contorta var. latifol ia. Tjg. 5, Ls .-dm- --- latidens in P. ------contzrtd vdr. Satifolia.- Fig. 7, _i. ---men's in -7. pnderosa. --- ...... 8. Frequency d i stri buti on of hcadcapsul e widths of /49 l arval latidens. '7 7 -I. --- ...... L I

9. Duration of developmental periods of 1. ...------latidens .. and 1. pini .P. ...-- laliio?id bark 25-3x ~n contorta var. ---" sandwiches at or-""' (sampl e sizes given below each bar). ..s.....l...... L.. 3 1 10. Survivorship within broods of -1. --latidens in -P. contorla var. latifolia at 25-35 C...... 3 3 "0. 11-12. Enlergcnce patterns f I. latidens From P. contorta var. Iatifolia at 25-35 8C.- ~rlr~ieid-ynfestedlogs. Fig. 12, L.abor;dtory-infested bolts...... 3 7 1 Tne bark beet1 e, -Ips --1 atidens (I.e(;onte) (Col eoptera :Scolytidae) , generally attacks the tops and limbs of dead, dying or weakened coniferous trees and/or slash, particular ly lodgepole and ponderosa pines, Pinus contorta var. lati fol ia Engelm . and -P. ponderosa Dougl. -ex Laws., in C__-- -- British Columbia (Bright 1976) Under favorable conditions adults may kill trees; during outbreaks of the mountain pine beetle, Dendroctonus ~derosae ---pa------

~opk., populations of -I. latidens may increase to such numbers in the crowns and slash of trees ki'l led by D. ponderosae------that they can successfu1ly attack and kill many small trees (Furniss and Carolin 1977).

In British Columbia I have found -I. latidens infesting boles of large- diameter pines. Within the area of a -D. ponderos~e-- infestation, some trees of substantial size may also be infested with I. pilli - --latidens or -.I. - (Say) 2 (J.H. Borden , pers. comm. ). -If mortality due to IJS- spp. has been mistakenly attributed to -D. ponderosae,- then damage caused to mature pines by ips should be reassessed to gain a real istic knowledge of their impact on the forest resource. As intensive forest management practices are implemented, operations such as thinning and spacing may result in large numbers of --I. latidens emerging from slash and attacking the remaining trees in plantations. - 1 Formerly ----Orthotomicus --latidens (LeConte) --sensu Hopping; Ips girildi Rlackman; lomicus -s@ifer -- Eichhoff; & longidens Swaine; -Ips ----latidens (LeConte) * sensu Swaine; Tomicus latidens LeConte (Bright and Stark 1973; Wood 1982). --.------m---- 2 Centre for Pest Management, Department of Biological Sciences, Simon Fraser University, Burnaby, B.C. V5A 156. 2

Relatively little is known about the life history or basic biology of

-1. latidens-. Blackman (1919) examined over 100 engravings made by I.- latidens in eastern white pine, -P. --Strobus L. Males are polygamous; each excavating a nuptial chamber in the phloem of a tree frorn which femles in his harerrl construct egg tunnels resulting in a characteristic star-shaped gallery in the bark, and sometimes engraved in the sapwood (Chamberlin 1958; Bright and stark 1973; Bright 1976; Furniss and Carolin 1977; Wood 1982).

Lanier [1966) and Lanier and Oliver (1966) have described a 'sex-ratio"

(SR) phenomenon in which females transmit a factor to their offspring . resulting in all-female broods. Several authors (Wood --et -al. 1967; Lanier and Wood 1975; Furniss and Livingston 1979) have observed -I. ---latidens responding to terpene alcohol pheromones being tested for other Ips spp.

Without basic information on the life history and population dynamics of -I. latidens, it is very difficult to assess either the direct irrrpact of

-I. latidens upon forested ecosystems or its interactions with other bark beetles. In the southern United States there was a 27X increase in attack density of -I. --avulsus (Eichhoff) on loblolly pines, -P. taeda L., treated with inhibitors against the southern pine beetle, -D. frontal is Zimmerman; all but one of the treatment trees died (~atterson--et al. 1982). As -I. latidens is sympatric with the aggressive bark beetles, -D. ponderosae-- and -I.

---pini , it is imperative that the biology of -I. latidens be known in order to develop successful pest management practices in lodgepole and ponderosa

Pine forests in British Columbia.

My objectives were to:

1. describe the gallery characteristics of --I. -.latidens in detail,

2. describe the behavior of adult and larval -1. --latidens within phloern tissue,

3. determine the number of larval instars, 3 4. estimate the duration of each stage, the generation time, and the interval

between fiight periods,

5. deterrrline the reproductive potenl;lal of -I, ---.-latidens, and

6. examine the irnpl ications of -1. latidens biology an forest pest management.

--.--.--MATERIALS AND METHODS-

COLLtCTlON OF BEETLES AND HOST MATERIAL

Uninfested bolts of lodgepolc and ponderosa pines, and ludgupolc pine bolts infested with either -1, --latidens or -I. pini were col!ected in 1982-

1983 from various locations between Manning Park and Princeton, B.C. Within

3 days the exposed ends of all bolts were sealed with hot, melted parafin wax. Infested bolts not imn~ediatelyused for rearing were stored at 4-12 ('c dnd 20-30% R.H. Uninfested bolts were stored outside in a roofed enclosure.

---Co lonies

Colonies to produce large numbers of I,- latidens---" and --I. 12ini were maintdined in sepdrate rearing cages at. 25-35 OT, and appro~imately43% i?.U.

Colonies were started by allowing 50-150 beetles reared Jrom ffeid-jnfestea bol ts to attack 2-4 iininfested bolts; attack usually occurred ~ith~ri a d~ly.

Whenever beetles seemed more inclined tn fly than altack, rile cages nc?inE covered w~thdarK pl ast~c. Emergent b~et1 es froiri mature broods wt'c collected dally from the cage wall s and stored on r;~oisterred tissue paper in glass jars at 4-8 0 C. capsules (No. 00, Parkc, Davis and Co., Ltd., Brockville, Ontario) were used

to restr~ctbeet1 e activity 'to a smal l area on a bolt. Beet1 es were placed witnin tj-mm-diameter holes made through the bark and phloem with a cork

borer. Each hole was covered with the long portion (8x20 mm) of a separated capsule, held in place with masking tape. Capsules were removed

to allow introduction of additional beetles and replaced with new capsules.

~rena-bolt-- techn~yue

Since pill capsules were ineffective in restraining -I. latidens, a

petri dish enclosure technique (Hosking 1972; Zanuricio 1981) was used, and modified to permit beetles to bore their own entrance holes through the bark. Holes (1 cm diameter) were made through the tops and bottoms of pldstic

petri plates (35x10 mm or 60x15 mm) using a hot spike. I he separated portions of the plates were affixed with ~y~lar~model1 ing paste (M.

Grumbacher, Inc., New York, N.Y.) to part~ally-debarked bolts with the open

side facing the bark surface. Beetles were jntroduced through the hole of each arena, and the holes were sealed with transparent tape.

-Bark-sandwich --technique A variet,y of bark "sandwich" preparations have been used to observe

scolytid behavior --in situ (Reid 1955; Hopping 1961; Thomas 1961; Beanlands

1966; Balogun 1969; Borden 1969; Schmitz 1972; Gouger --et --al. 1975). The basic design consists of: (1) a viewing surface of glass or plexiglass,

against which is pressed (2) a bark section with the phloem tissue inward, (3) a glass, wood or plexigldss scction on the outside of the hark sectisvl torminq the "sandwich", (4) bolts, clamps or tape to hold the prepardtion together, and sonrutimes (5) hot pardfin wax or tape to seal the expbsed edges of the bark section.

Iwo major drawbacks of existing sandwich designs are: (1) local isat.ion of pressure along the per iphcry of the sandwch rather than the cent-rdl portloti, thereby allowing small beetles to leave the phloern tissue without boring through tho bark, and (2) rupturing of corripressed phloem tissue directly beneath clamps or adjacent to bo1 ts holding sandwiches together.

Therefore, I modified the technique by piacing the bark section in a plex~ylassbox with a styrofoam pad on the outside (Fig. 1). The inward bow of the plexiglass top of the sandwich caused by the sides 9f the box acting as fulcra, and the spongy nature of the styrofoam, resulted iti most of the pressure fro^ 4 cldmps being everlly distributed over the entire bark ~urfri~e.

Ihis method rcsult.ed in a bark pi-eparatlon w-ith rnini!nal damage to phloem

4 ;rc.. ~+h>ueand tnax5111~tiiol~laci between tnc phiocm dad viewinq surfaces, thereby ensuring reliaSle observations of beetle activities -in ----situ. Sandwiches were rliade in boxes of 2 sizes; intern;: dirnens ions of 13-3x

20.U cm ana 20.0~30.1cm. Bark sections corresponding l,o these (1 irnensior~s were removed with kn~feand chisel from un~rtfestedaild part~ally-debarked bolts, and placed into each box with the phloem against the bottom. A styrofoam pad and plex~glasstop were then added, arid the sandwich clampeu shut and sealed with acrylic-latex caulk.

Beet I es were introduced through 8-mm-diameter holes [in the yl exiglass top of each box) that extended Lht-auyh the styrofoam layer to the hark surface. Small sandwiches had either I entry hole in the center of the prepar~itionor 3 $paced s cm apart in a V-confiquration. Large ~dndwichcs Fiy. I. Plexiglass-sLyrofoam bark sandwiches. had 5 entry holes approximately / cm apart in a W-conf iyuraLion.

SEX DlFFERENTIA I 1011

Determination of the sex of adutt -1. latidens using seconddry sexual characters described by Lanier and Cameron t19b9) proved di tficult and unreliable; the kars ...----...stridens on the frons was rarely detected. Therefore the el ytra l decl ivities of 378 adult beetles were examined for sex-specif ic, characters in order to develop soiiie re1 idS-11ity in experl~~~euts.[he sex (,f each beetle was then determined by examination of the dissected genitalia, and the specimen mounted for reference. Thereafter, mounted bectlcs were reviewed before live beetles were examined and separated into 3 categories: males,'fernales and unhnowns. Beetles in the unknown category were not used in rearing experiments. In addition to reviewing mounted beetles, I also examined 15 groups of 10-12 live beetles during the first month of experiments in which sex was a controlled .factor. [he declivity of each beetle was exami~red for sex-speci fic ~hdr;i~tt?r.s~nd the djsscctcd 5c:;S t;? ia ex;nii;;cd for verification of sex.

-Gdll ery characteristics---- and behavior

I attempted to rear broods or' --1. --latiderls ------#any times: 7 times a<, mass colonies, US times In 50 bark sandwiches, dnd 254 times OH 44 arend bolts with 1-15 arenas per bolt. A total of 342 separate galleries was dsed to estimate various population parameters, such as fecund l ty and sex rat ius, determine gallery characteristics, and observe the behavior of --I, latidcrls.,--"- ---.-

For comparative purposes 1 reared broods of -1. ----pini: 5 times as mss colonies, 7 times in sandwiches and 24 times in 3 arena bolts For a total of

31 separate gall eries. Daily col 1ections OF emrnergent beet'l es from colonies of both species were used to determine emergence patterns from field- ana laboratory-infested logs. Sex ratios amongst emergent beetles were obtai ned by examination of dissected genitalia.

Harem size was estimated by the number of females a1 lowed into each nuptial chamber. Individual males were localised at 29 sites on 2 ponderosd pine bolts by the pi1 I-capsule technique, and restrained within 23 drenas on

2 arena bolts of lodgepole pine. tach male received 1 female/day or every secotld day after evidence of boring was visible, for a total of 4-8 females per ma le. The sex of all beetles was verified by exarn ination of dissected geni tal ia.

Oeve I opinent

The number of instars was determined by measuring headcapsul e widths of

749 1. '!at;dens larvae exc:'scd from 79 broods, reared on 10 Icidgepole pi;;? .- - bolts, at ~ntcrvalsrdnging from 15 to 104 days after infestation. The greatest wldth of each capsu le, perpendicular to the body axis and along the median plane, was measured with an ocular rnic~ometer.

I exainined 17 ga l 1 eries of .-J. iatidens-- - -- in bark sandwiches to estimate ger~eration and deve lopt!:ental ti!oes for each stage of the life-cycle at 25-

35 OC. In 15 sandwiches i~~onogainouspairs were used, while in 3 sandwiches 2' females and 1 male were introduced into each entry hole. Comparisons were made with 6 galler.ic?s of -1. pini in bark sandwiches at 25-25 % Mnnogamoils pairs were used in 5 sdndwiches, while the sixth had 2 females with a maie.

Da~lyobservations were made unti l a1 l viable larvae had developed to tertera 1 adults or until excessive fungal growth or lack of visibil ity precluded any observations. Sandwiches were then dismantled and the sex of brood adults determined by examination of dissected genitalia.

-- -- Brood survivors~

Brood surv~vorsh~pwas determined from 101 galleries on 8 arena halts and 63 galleries in 33 sandwiches, for a total of 164. In a71 rearings monogamous pairs were introduced into each arena or sandwich entry hole.

Single, monogamous pairs of -I. -----latidens were introduced into each of 22 o arena-bolts, and kept in separate rearing cages at 25-35 C, ir~order to drtcrmine the rSeproductive success of ~ndividtrdl Females. The sex of a13 brood Lidults wers dotermined by exdrninatidn of disseiteJ senital ia.

SkX Dl FFtKENTIAT1ClN

Consistent! y high accuracy 1;:;th;n xal c and fc;;s?c categories 2s determined by exaii~Snadion of cli ssc?cti!d genif.al is (T(7bl e 1), permi tted re1 iable use of individual -.I. iatStiens of kmwn sex -in rear-ing expcriinents.

Males tended t.o have larger becl ivi tal spines than f'ernales, pdrticular1.y the third one. In males the third spine was usually Song and cyl indrical , so~wtiincstapered, rarely t.r isngular, and parallel to ur divergent from thc bocly axis; in fernc)les the third spine ranged from triangular to tony and tapered, rarely c~yl -indrical , and parallel to or convergent with the body axis. Beetles were categorised as unknowns if deciivital spines were intermediate in size ~ildif the third spine was parallel Lo the body axis, but not triangular or cylindrical.

Single, qua1 itative traits, efficient for Gal ifornian populations ApriI-Mdy L983 Sep t 1!K1 Ca tegr~ry ------Z 2 1 Dctei ;1r i rlecl(:,) Det~rm-inrd! ?') Observed - --. 0 b s e r v e d I ------Ma 1 e FF~1 e Fla t e Fcn~I u

Unknowns 17 43. .2 58.8 87 43.7 56.3

I bdscd on se~cildarjsexua l characters cf el ytral decl rvi tics. 2 bdsed on exdmiridt Sons or di ss~cted qenit a1 i3. 12

(Lanier and Cameron 1969; Bright X9i6; W~od1982), are not easily used by

persons unfamiliar with -I. ----latidens -- nor are they adequate for differentiatinq

the sexes of a s-iqn~ficantportion of beetle populations in British Coltrrnhin;

the sex of 23% of adults examined could not be determined on the bdsis cil

dec1 ivita3 characteristics. Hence for Brit-ish Columb.ian populations of

latidens,- sex should be determined on the basis of rnultiple cieclivital

characteristics, at least some of which should be quantitative and normal

to body i~iedsure~wr~ts.

GALLERY CI-IAKACIERISTICS AND BEHAVIOR

3.I randicoll - ..- --- -. .- -- is- (Eichhoff)JAll and Anderson 1972), --1, -latidens galleries may be initiated 5y either sex, Ma-IPS initiate most galleries, excavating

female-constructed egg tunnels radiate outwi~rd, F'e~na'lesmay initiate

galleries in female-biased ?ex rdt~os-ituat.iiins; of" 178 fcii3ait:s introdwceri

into 27 s?nyIc-wlc arcrlds ciri iodyepule and pol der'osd pine, IZ in]tidtecd

galleries, were .joined by the r~sidet~trndle, and oviposited. The males did

not construct nuptial chambers in female-ini tiated galleries, and left

behind galleries containing oviporit~ngfemales to join females in female-

iriitidteii galleries.

Seventy-one s~ngiefemales constructed tunnels, possibly in preparation

for mates or as a consequence of feeding. In 3 arenas, 3 ovipositing

females were found alone in fernale-initiated egg tunnels, Since mating is

necessary before oviposition can occur, even in SK females, (Lanier and J 3

Oliver 1~661,either males ana/or reillales travelled freely between galleries, or temal es mated prior to int,roduct ion i nto arenas. Pre-emergerice mat i ny

does occur in I.-I. qrandicollis---- (A11 and Anderson 197.2; Witanachct-,i 198U), the proportion of mated females increasing with titiis spent as adults under the

bark to as high as 89%.

Males in sandwiches blocked gallery entrances with their duclivitics,

presumably defending their harems. Males in bolts appeared inefficient in

preventing entry by ott~ermales 7nto galleries; in 7 of 15 multip2e-male

arerias, up to 3 rndlcs were found in the same gal lery. Males seemed more

efficient in preventing entry by females; 48% of Females did not enter a male's gallery, and initiated their own. In -1. --..------.-pdraconfusus Lanier male gliarcllng behavior does limit tne numbcr of fftriralcs accepted ir?t,o a gal lcry

to 3 (Borden 1967).

Frass (boring dust and fecal pellets) prodaced by fernales in

constructing egg tunnels was scooped behind them, ptiqhed with their elytral

drc?ivit:zs ta the iiirptia: chamber , and rxmjved Lo Lhe outside by the

resident male. IF the male was absent, frass accumulated in the nuptial

chamber, preventing passage by females between egg tunnels and the bdrk

sau'f ace.

Ventilation holes as used by ---Scolytus ----ra tzebuM Jans (Me1 'ni kovd i964) to regulate humidity withan gdlleries were common in --I. -- pini gal leries,

but rare in -I. ------latidcns gallerlcs. Possibly -1. laticlens--.- breeds in materr'al that rclrely has an excezs level of moisture. In the laboratory, adults

swwd lo prefer the drier sectiotls of phloem in the outer barb and ar, the

ertcls of bolts. Mating and oviposition

Frequent shoving matches occurred between females and the resident male at the junction of egg tunnels and the nuptial chamber, particularly preceeding mating and oviposition.

As in many other scolytids (Kirkendall l983), --I. -latidens mated repeatedly; in all 12 matings I observed, females had previously oviposited in their respective egg tunnels, and 4 matinys involved the same pair of adults. Mating lasted 20-120 sec; comparable to -I. ---avul sus (Gouger -et --a1 .

19751, -I. pini (Thomas 1961; Schmitz 6972) and -I. cembrae- Heer (Balogun .l97O).

The copulatory position of -I. latidens was similar to -.T. avulsus but di Fferred from -1. pini and -I. cembrae, with the body axes perpendicular to each other rather than parallel .(Fiq. 2).

Oviposition was only observed once in a bark sandwich, and was similar to -1. pini- (Schmitz 11172) and -I. ---avulsus (Gouger --et a1 . 1975). The female excavated a niche in the wall of an egg tunnel, pushing most of the boring dust into the nuptial chamber. Once the niche was complete, she backed into the nuptial chamber, turned 180•‹, re-entered backwards, and then attempted to oviposit -In the niche. Following 3 oviposition attempts she laid d single egg, qu'ickly withdrew from the egg tunnel, re-entered head-first, and packed the egg into the niche with some of the boring dust remaining after niche construction. Between attempts the female withdrew into the nuptial chamber, re-entered head-first, and "inspected" the niche, making minor alterations.

Pushing occurred between the female and the resident male every time the

female tried to enter the nuptial chamber to turn around.

Niches were excavated in both walls of an egg tunnel, and sometimes in the top and bottom if the phloem was thick enough as in ponderosa pine, at a

rate of 1.95 egg nicheslday; O.78X slower than -I. --pini (t test, p< 0.1) Fig, 2. Uopulatory position af -I. -..-----.latidens in -P, ...--contorta -. - var. latifolia--- bark sandwiches.

17

(Figs. 3-41. The distribution of niches ranged from even along both sides of an egg tunnel to all on one side.

In lodgepole pine, the smaller eggs of -I. latidens- were laid singly in niches, spaced closer together than egg niches in -I. pini-- egg tunnels; 0.95 and 0.54 egg niches/rnm of egg tunnel, respectively (t test, p < O.Ol)(Figs.

5-6). In jackpine, -P. --banksiana Lamb., and eastern white pine, -I. pini constructed U.29-0.32 and U.5U egg niches/mm of egg tunnel, respectively

(Thomas 1361). Niches made by --I. latidens were spaced farther apart in ponderosa pine (0.51 egg niches/mm of egg tunnel )(Fig. 7) than in lodgepole pine (t test, p< 0.01). Kirkendall (1983) suggests that niche spacing by female scol ytids is a function of phloem quality; in Pityathorus lautus- E~chhoff,niche spacing was strongly correlated with nitrogen content and total avai lablc carbohydr;ltes in phloem of the smooth sumac, Rhus glabra L.

lntraspecitic competition is the most important mortality factor in broods of -I. pini (Schenk and Benjamin 1969) and scolytids in general (Cole

1973, 1975; Ogibin 1973, 1974; Birch 1978; Berryman 1982). Female scolytlds sucn as 1. latidens may be able to assess resource quality of phloem and space their eggs along egg tunnels in order to minimise intrabrood mortality.

Cannibal ism amongst larval -I. --- latidens, consistent with observations on other scolytids (Schenk and Benjamin 1969; Berryman and Pienaar 1973; Berryrnan

1974), did occur and suggests that intra brood competition may occur amongst 1 arvae.

Linearity of regression lines (chiC test, pc o.Ol)(Figs. 5-7) suggests that niche spacing is constant regardless of egg tunnei length for both -I.

---latidens and -I. pini for a given qua 1ity of phloem resource. Linear relationships between the numbers of eggs and egg tunnel lengths are known for -I. cembrae (~alogun1970) and -I. .PL-'ni (Thomas 1961). A constant spacing Figs. 3-4, Rate of niche construction and oviposition by ips in -P.

----contorts var. lat~folia-- at 25-35 'c. Fig. 3, -I. --latidens. Fig. 4, -1. e. REARING PERIOD (Days after infestation) Figs. 5-7. bpaciny of niches In egg tunnels by feinale ips at 25-3Pk.

Fig. 5, -1.@ in --P. --eontorta bar, ---latifol ia. Fig. 6, i. -1atjdelis in -P. contorta var. ----latifolia. Fig. 7, --1. latidens in -P. pndcrosa.--- 1 latidens on P ponderosa y=506+051x r 0 761

EGG TUNNEL LENGTH (mm) 2 2 of egg niches, rather than a variable ovipos~tingstrategy along an egg tunnel (i.e. spacing niches in the middle of an egg tunnel farther apart), may be an optimisation strategy where toss due to ~ntrabroodcompetition is offset by tho risk of dying before a full complement of eggs 1s laid,

Fecundity of --I. latidens was 64.4 eggs/female (S~=16.26; n=17), not significantly different from that of -I. .-pin1 (66.6 eggsifema le; SD=31 .39; nz9)(t test, p) 0.5), and comparable to other ips, -I. ---arnitinus (Cichhoff) (Ziiir~rarid Soldan IYSI 1, -I.

------..a.vu1sus (Gouger et -al, .--. 1975), and --I. ----cernbrae (Balogun 1970).

--ttslrcm slze and egg tunnels

the number of egg tunnels constructed within monogamous -I. ------latidens galleries increased over time, with mature galleries havinq 3-4 egg tunnels

(Table 2). Newly-laid eggs were usually found In only one egg tunnel of a gal 1 ery, the other, older tunnels having only larvae. Semaies generdl iy constructed only one egg tunnei at a t-irne, h~ti~uuyhd few a?ternated between tunnels. Egg tunnels had a mean length of 29.8 mrn (SD=9,77; n-45) and contained an average of 27.4 egg niches each (SD=11,45; ~~59).

Since female -1. ---latidens, ---Pityophthorus ------.iautus (Kirkendall 19831, and

-1, -- paraconfusus- (~arr1969) may construct more than one egg tunnel per gallery, harem size in scolytid specie5 cannot always be i!ifeu'rerl from the number of egg tunnel s in each gal lery. Cook ct a I, (4983) iinde the same observat.ion for -I. .-avu 1 :;[is,-- but siiggest that mu-l tip'l e egg tunne'ls per gal lery are a consequence of multiple monogamous pairs of beetles us.ing the sam nuptial chamber rather than single females constructing multiple egg t.unne1 s. Hence cxarnination of scolytic! gal 1 cries in the field to ddetemine productivities of individual females should be verified by laboratory Table 2. Mean number of egg tunnels constructed within 65 separate

Egg tunnels Days after N~imber of ---- infestation gal leries Total ~ean/femal e' I

J. sigrlificant differences amongst means, Kruskal-Wall .is test, p C 0.01 experiments. Bark beetle attacks are uniformly distributed over bark surfaces

(shepherd 1965; Berryman 1968; Hedden and Gara 1976; Ni llsen 19781. Each gallery has a limited phloem resource to utilise for brood production. Hence the construction of multiple short egg tunnels hy --1. --latidens, rather than single long tunnels, per gallery may maximise phloem use while minimising intergallery competition amongst larvae.

-I. ---latidens is polygynous (Blackman 1919). Results of some rearings to determine harem size were inconclusive due to mu1 tiple males in some . galleries, female-initiated galleries, lack of male fidelity, damage during debarking procedures, and loss of femalcs from pill capsules and arenas; 40 and 10% of females were lost in p~ll-capsuleand arena-bolt rearings, respectively. The mean number of females within galleries associated with slngle males was 2.5 females/male (SD=1.56; n=39; range= 1-7) in lodgepole pine arena bolts, significantly greater than the mean of 1.8 females/mal

\SD=0.73; nz21) found in ponderosa pine pill -capsule rearings (t test, pc 0.01).

In moderately polygynous scolytid species, 2-4 egg tunnels per gal? are typically observed (Kirkendall 1983). Assuming that there is an optimal number of egg tunnels that should be constructed in each gallery then competition should exist among --I. --latidens feinal es in po lygynous gal 1 eries for egg tunnel sites;.as harem size increases, competition for oviposition sites amongst females should increase. Therefore, in order tomaxl'mise reproductive success, females in polygynous situations would be expected to re-emerge and attempt to estab l i sh additional broods, a strategy typical of many scolytids (Borden 1982 1 . ------latidens in monogamous bark sandwich galleries did not re-emerge while females in log colonies did. As harm size increases, male-bids in the operational sex ratio (Ernlen

1976; Emlen and Oring 1977) should also increase assurillrlg that not a1 1 remining males die or emigrate. Selection should favor a strategy whereby a femal e leaves a gallery when the probability of finding another mate and esta bl ishing a new hrood is high enough to offset the r isk of predation, or death, and the loss of further progeny in the abandoned gallery. A female should leave a gallery either if the harem is too large or when she has laid a coniplement of eggs suitable for a given harem size, In moderately polygynous species, Phloeosinus------bico lor Uru I1 , --Ph. -----thuyae Perris, -Po1 ygraphus -- -- rufipennis, - and --ScoAtus piceae (~halrle), the nrxniber of eggs per egg tunnel decreases with an increase "in harem size. In Pityzhthorus- --.--.------.lautus, differences in the time spent in a gallery ovipositing arise due to phloem quality and size of harems (Kirkenda'l'l 1983). In .-I, -latidcns gal ter~es,the number of eggs/gal'lery, and egg tunriel length, decreases with an increase in egg tunnel s/gall ery (Bl ackman 1919).

Changes in thc frequencies of ccpufation, frass removal ur pkt,h matcnes could serve as indicators of harem size and/or n~diefitness --Idtidens galler~es. Alternatively, females may complete egg tunners re-emerge if they are unable to start new egg tunnels.

l here may be a selective advantage for males to limit the size of hareins as in -I. parcfcunfusus (Borden 1967). tven though the rwnber of eggs per gailery (and per male) increases with harem size in polygynous scolytids

(Kirkenda ll 19831, the reproductive success of a n1a1e may decrease if too many eggs are laid; phloem is limited and a given gallery may only be able to susta~na tinite number of progeny. Surv-ivorsh-I p WI thin -I. paraconfuws.---- hrooas in galleries containing 3-4 females each was lower at an attack density of 2 rna1es/dm2 than I ma leiam2 {Liqht -et -- ---a1 . 1983). 2 6 Some scolytids deposit fewer eggs per gallery in response to increased attack densit,y (Berryman 1982). At high densities spacing between galleries may approach a lower threshold, resulting in less breeding material per gallery. Re-emergence in response to high attack density may occur if harem size is correlated with attack density or if phloem quality at intergallery

boundaries deteriorates, assuming females can assess harem size arid phloem

quality. Female --I. ----. paraconfusus laid fewer eggslegg tunnel and re-emerged 2 earlier at a density of 4 parent females/dm2 than at 2 parent femalesldm (Light et al . 1983). Therefore, it seems. 1 i kely, and testable, that fernal es of po lygynous

scolytid species like -1. --latidens may be able to assess attack density and harem size, and adopt appropriate reproductive strategies.

DtVELOPMENT

-----Number of larval instars Dyar's rule (Dyar 1890) has been successfully used to determine the

number of larval instars in scolytid species (Thomas 1961; Wil kinson 1963;

Hosking and Knight 1976). The distribution of the frequencies of

headcapsule widths of 749 -I. ---latidens larvae clearly shows 3 instars ~n the

larval stage (Fig. H), typical of all species in the tribe (Wood 1982).

Headcapsule width means for successive instars were significantly different,

and exhibited a regular, geometric progression (Table 3), as predicted by

Dyar's rule (Taylor 1931; Gaines and Campbell 1935)

Duration of 1 i fe stages

One brood of -I. pini and 4 broods of -I. ---latidens in bark sandwiches were

used to determine the duration of life stages and generation time. Fig. 8. Frequency distribution of headcapsule widths of 749 larval ---Ips latidens.

Table 3. Mean headcapsule widths of larval instars of Ips latidens----- (n=74~).

.--_l__l_."------."------

It,>La,

'means s~gnificantly different, Xruskal-Mall is test, p C 0.001.

'ratio of the mean headcapsule widths of one instar to the previous instar. 3 0 Deve7opment of each stage was significantly longer for 1. 1atfderis than for -I. pini (t test, p <0.01)(Fig. 9). The generation time (egg to tenera! adult) in

-1. -latidens was 2.97X greater than- in "-I. pini (t test, p c 0.01), due mainly to a prolonged larval stage. rieither quiescence nor diapausc wds observed dur-ing the larval stage at 25-35 'c. There were no significant differences

~n the duration of each stage between broads of -1. ----.--1 atidens (Kruskal-Wallis test, p > 0.38).

The mean generation time for -I, -pini reared -in bark sandwiches was

42-70% shorter than in the field (~rebble1933; Reid 1955; Thomas 1961;

Schenk and Benjamin 1969). By c~mparinglaboratory data on --I. ------pini and I,

-----latidcns --- to f~elddata on I.-. pini at Hlack Sturgeon take, Ontario (Thomas 1951), and in Fredericton, New Brunswick (Prebble 1933), 1 estimate that In south-central British Colunibia, the egg, larval, and pupal stages of -I.

-----latidens should last 9.8-12.3, 37.4-67.9, and 93.7-17.6 days, respectively; comparable to many scolytids (Wood 1987). The generation time for -I.

-----Idlidens shouid range from 64.2 to 99.4 days. Using field data tor --I. gin1 near Kocky Mountain House, Alberta (Reid 1955), the generation titue may last up to 124 days.

Brood survivorskip----

Mortaltty within broods of T,- latidens occurred primarily from egg to secvnd instar Idrvae, with survjvot-ship within mature broods averagir~q56.0%

\Fig. 10). In dn independent experiment, the mean reproductive success of 17 monogamous pairs in lodgepol e pine logs was 36.5 tenera1 adults/pd ir

(~~=18.85);assuming a mean fecundity of 64.4 eggs/femal e, brood survivorship was 56.1%. Fig. 9. Duratlon of developmental periods of --I, latidcns and .-J. -pini in -P,

-contorts var. ------latifolla bark sandwiches at L5-25 'C (sample sizes given be1 ow cach bar-).

Fig. 10. Survivorship within broods of -.I. .--.- latidens in -.P. contorta ---- var. --- l alifo1 ia at 25-35 OC. ------Mean survival of mature broods EMERGENCE PATTERNS

Yex ratlo - .-*- "- In ips the typical sex ratio amongst emerging adults is close to 1:1, while the sex ratio amongst attacking beetles or successful beetles is generally female-biased at greater than 2 females/male, This phenomenon occurs in -I. ----paraconfusus (Struble and Hall 1955; Cameron and Borden 19671, -I. p1ni (Schenk and Benjamin 1969; Schm,itz 1972), -I. --call~r~hus - -- (Cook et .-al.

~983)dnd --I. ~JJICQ-~~R~US(Annila 1911). In --I. ------'latidens the sex ratio amongst. teneral s within broods arid emerging from logs wat; riot s ignif icantly different froin 1:1 [t test, p>0.5). There was no evidence of the 'sex ra,tioi condition of all-female broods (Lanier and Oliver 1966).

Annual fl ight periods "- --A - Pest managernewt practices against OarK beetles are tjmed 2r0i~ndflight peri;oas when adults attack new hosts. lhe est~matedgeneration time of

64-124 days for --I. -latidens --.------may not be a rel~abfeestimate of the per~od between fl ~ghtsof attacking adul ts and thcir subsequent offspring. In la~oratorycolonies, first emergence of -I. latidens progeny occurred 60-65 days after infestation; approximately I.GX longer than the generation time in bark sandwiches,

Maturing tenera1 --1. ----laticlens spent cons.iderab1 e tinie feeding under the bark of "lodgepole pine; 1ri eastern white pine, tenerals feed for weeks arid sometimes even mon'ths before emerging ( Blackman .19X9). In Wiscons'iri, -.I. .eini took 5-9 days to develop full coloration and sexual rnatur\ity, and an additional 5-11 days to feed before emerging from logs (Schcnk and Benjamin

1969). In -I. -ty~0,qraphus -- L., _I. amitinus and Pitpsnes chalcgrauhus L,, ------_I -- -. "-.-- L-- spermatel~os~sand v~tellogenesisoccurs primarily during the maturation feeding period prlor to emergence, even though gonads are completely developed prior Lo feeding (Zurnr and Soldan 1981). Thc flight muscle volume of' -1. ----- paraconfusus increases 20X during maturation feeding (Borcien and Slater 1!J69 1 . L~pidreserves of _D_. pseudot~-u~;~~e_Ilopkins adults build up to 20% of total dry body weight before they are optimally-ready for dispersal flight

(Atk-iins 1966d).

The ~ntervdlbetween fl ights of -1. ---- 1 atidens adu? ts and their subsequcni. broods may be so lengthened by maturatdon feeding, in preparation for dispersal flight and brood production, that only one generatior) can wcur per ymr in south-central British Columbia. This hypothesis is supported by research in 1983 near Manning Park, B.G., which suggested a single major flight period between late May and early June, and a minor peak in late July, probably representing re-emerged adults (J.L. adde en^, D.R. Mil I t'r and J. ti.

Borden, unpubl ished results). -

Therefore -I. -- !atidens in seuth-central British Cclumbia prob;Sly has a slngle generation per year with a partial second brood in late summer, as does -I. ----latidens in white pine in New York (13lackiiran 19191 and two srnall and related ipine species, Pityogenes -----knechtel i Swalne and ---Urthotomicus - vic~nus.- - - (Le~onte),occupying similar niches in A1 bertdn lodgepol e pi ne forests (~eid

1955).

--Emexence -- synchrony-- Ninety-one percent of overwintering --I. ------latidens in field-i~festcd bolts of lodgepole pine emerged in a 25-day period (Fig. 11). Emergence from

'~aculiy of Agricultural Science, University of Tasmania, Hobart, Tasmania Australia. Figs. 11-12. Emergence patterns of --I. ----latidens from -P, --- contorta var.

..------latifol ia at 25-35 OC. Fig. 11, Field-infested logs. Fig. 12, Laboratory- infested bolts. r-r------I7

FIELD-INFESTED LOGS

PERIOD (Days after collection)

ays after infestation) 3 9

I aboratory-infested lodgepol e pine logs was protracted significantly more than from f ield-infested logs (F test, p < 0.~1); 90% of the beetles emerged over a 75-day period (Fig. i2).

Synchrony of emergence by overwintcring -I. ----latidens niay be a consequence of differential mortality of life stages leaving only mature adults by spring,

Alternatively, develdpment may continue at low temperatures such thdt most of the broods are flight-ready adults by spring. In support of the latter hypothesis, mass fl ight by -I. typographus-- occurs only when ambient air temperature exceeds 20 OC, yet brood development continues even at 5 OC . (Anni 1 a 1969).

Like other scolytids (Atkins 1966b), -I. latidens exploits ephemeral and patchy habitats, such as the winter" accumulation of wind-downed and diseased trees. Selection should favor individuals emerging and establishing broods as soon as environmental conditions are favorable. Late emergents should be selected against since they would not be as successful in finding adequate phloem or mates.

IMPLICATIONS TO FOREST PEST MANAGEMENT

---Ips ----latidens is not recognised as a significant forest pest. It does not aggressively attack 1 i'ving trees and its population growth is l imited by only 1 generation per year.

However, it is ubiquitous, breeds in severai conifer species, especially in slash, and has a reproductive potential comparable to other ips. --I. ----latidens could become a pest in intensively-managed forests of the future. In Georgia, damage to young plantation trees from prescribed burns and thinning operations increases the probability of infestations by spp. (Wil kinson and Fotz 1982).

Several management imp1 ications should be kept in mind. Monitoring of , 4 0

"-1. ------I at~dens popu iat-~ons,particularly within unchecked --D. ponderosae------infestations, can only be done by the labor~ousand tedious method of exanlining bark samples. -I. ---latidens does not cause conspicuour, pitch tubes as does -D, ponderosae,----- nor does it produce copious amounts of frass like --D.

I!-onderosae -.-_. or --I. pi~-!. Although chemical attractants are knovm for --I. latidens (Wwd --et a?. 1976), they have not been ver~fiedas pheromjnes nor tested as monitor~ng Loo l s.

The possibality exists that effect~vecontrol of either --U. ----ponderosae or --I. pin1.- populations could result in compensatory population growth of and damage by -I. -latidens. Routine sanitation practices such as efficient slash d isposdl , and sanitation/salvage logging in -D. pnderosae and -1. --pini infestations, should reduce the probability of attack and infestation by -I.

-.--latidens. However timing is critical; -I. ---Idtidens emerges early in the spring

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