, VOl.. (1966), DEC. 1, 1966 JOVHXAL El'iTO.\IOL. SOl'. BIlIT. COIXMI!IA 63 THE fMMATURE STAGES OF Cpf1o('orixa bilida (HUNG .) AND

C. ('xp!('/a (U HLEH) (: CORIXfDAE)

G . G. E . SCUDDER Department of Zoology, University of British Columbia, Vancouver

INTRODUCTION rately in the corresponding lake wat­ er. In this way, C. bifida was reared a study of the ecology and In to the adult instar ana C. expleta in a physiology of living through the first three larval instars. s of soda lakes in central British serie All drawings have been made with identify Columbia, it was essential to a squared reticule eye-piece or Cam­ the larval instal'S of two s pecies of era Lucida, us ing both compound and Cenocorixa, which often occur sym­ stereo-zoom microscopes. The spines of larvae were patrically. This was necessary in or­ on the hind femora usually only clearly visible when legs to work out the details of the life der were mounted in polyvinyl lactophe­ tify with cycle and be able to iden nol or other similar mountant and certainty, used in experi­ viewed at magnifications over 150x. describes the im­ ments. This paper The terminology and characters l,WO species, mature stages of these in the larval descriptions fol ­ and C. expleta utilized C. bifida (Hungerford) low Cobben & Pillot (1960). However, species have been pre­ (Uhler) . Both I have interpreted the surfaces of the from British Colum­ viously recorded legs differently. The surface of the (1960) . bia by Lansbury hind leg seen in dorsal view is mor­ and MATERIALS and METHODS phologically the posterior surface so interpreted. Likewise the surface tages were obtain­ is The immature s n ven trally is the anterior face , regular sam­ see ed in two ways. Firstly the morphological ventral surface be~ obtained in field ples of larvae were ing the one towards the body eggs were ob­ collections. Secondly, when it is at rest or swimming. tainedfrom adult insects and reared. Gravid females were taken from EGGS Lake in the White Lake (" nd Long date it has not been possible to British Co­ To Cariboo regiOl e of central distinguish between the eggs of the and were trans­ lumbia in April 1966 two species. Both have top-shaped Hl one gallon ported to the laboratory eggs, with a very short stalked disc. Thermos j ugs, half filled with water. chorion, height 0.78 mm. and natural s mooth Insects were then placed in 0.57 mm. The egg of C. bifida dishes with width lake water in plexiglass shown in Fig. 1, just before hatch­ netting f or is vegetation and nylon ing. At eclosion, the apex of the C and uncl eI' them to cling to . At 20 ' chorion splits into 6-8 wedges. natural light conditions, fe males laid ratory, C. expleta usu­ eggs within 48 hours. Th ~se eggs were In the labo the walls of the con­ separated from the insects at fre­ ally laid eggs on laid most eggs quen t intervals: this was to prevent tainer, while C. bifida or plastic screen. them being used as food by the fe · on the vegetation has been found males. Batches of eggs were placed In the field, C. expleta boulders and finger bowls with the a ppropriate to lay eggs on rock in the leaf and kept at 20 °C and under bifida on vegetation, often in water sub­ al light conditions. Larvae on sheath of somewhat decayed natur this may emergence were fed every other day merged grasses. However, oviposition habit of on young brine shrimp (Artemia sal­ not be the only ina (L.» which were hatched sepa- the two species. 34 J OU It:'>A L E:'> T O ~\()L . SIl ... BI

I

Fig. I-Photograph of the cgg of Cenocorixa bifida just before hatching.

LARVAE dense long h airs. Most instars with (1 ) General descript ion of Ce nocorixa a dis tinct comb on hind tibia dis tally larvae : on posterior side. Rostrum with transverse furrows ; ( 2 ) Separation of species frons not grea tly hirs u te; eyes red. The following couplet will sepa­ Pa la spatula te; middle legs with tar­ rate th e la rvae of C. bifida from those sus lon ger th a n tibia; hind tibia pos­ of C. expl et a: teriorly with a row of 7 moveable Pa la with a pical lower palmar spines. Meta sternal xiphus short and bristle situa ted on a distinct prom­ equilateral. Abdomen laterally mod­ inence; terminal claw relatively erately convex; dorsal a bdominal slender , hardly thicker than pre­ scen t gland and opening on tergum a pical lower palmar bristle (Fig. III obsolete; scent glands a nd os tioles 9) C. bifida on terga IV and V distinct, the osti­ oles paired ; abdomen without distinct Pala with a pical lower palmar colour pattern. bris tle situated on :1!1 indistinct prominence; t erminal claw dis­ Latter ins tal's with a dense h a ir tinctly thicker than preapical low­ covering on mesonotum, but without er palmar bris tle (Fig. 10) this reaching a nterior ma rgin (Fig. C. expleta 6) ; h a irs on median area of a nterior mesonot um short; mesonotum with With th e above characters, it is hind margin covered wi th long hairs possible to separate the species in only in middle, the la teral areas bare each larva l ins ta l' and in the adult. and r elatively broad . Metanotum (3) Key to la rval instal's withou t long hair coverillg, but with The following key will separate sparse short and slender setae; inner the instal's in both C. I)ifida and C. margin of wing pads with line of ex pleta. JOUR~AL E NTO ~rOL. Soc. BUIT. CULCMlllA . VOL. 63 (1966). DEC. 1. 1966 36

1. Meso and metanotum with cover­ C. bifida. The descriptions below omit ing of long hairs on at least part· most of the characters of instal'S hind femur with tuft of long hair~ found in the key. In the counts of antero-ventrallY and with 4 short bristles dorsally; hind tibia with spines on the femur, all totals cited row of dense swimming hairs pos­ omit the two apical spines found at teriorly ...... 3. the apex on anterior and posterior - Meso and metanotum without long surfaces. dense hair covering; hind femur FIRST INSTAR (Figs. 2, 4, 11-12): pala without tuft of long hairs antero­ WIth 12 lower palmar bristles; fore ventrally, but with 5 long out­ ~emur anteriorly with 4 spines; hind standing setae dorsally; hind tibia femur w.ith 5 long hairs dorsally, 4 without row of dense swimming short spll1esposteriorly and 3 short hairs posteriorly, only a few scat­ spines anteriorly; hind tibia with 10 tered hairs present...... 2. moveable spines dorsally. 2. Postero-Iateral corners of meso­ notum curved distinctly caudad; SECOND INSTAR: pal a with 14 lower hind tibial comb with 2 spines; palmar bristles; fore femur anterior­ hind tibia with 5-7 long hairs pos­ ly with 4-5 spines; hind femur with teriorly...... second instar 5 long outstanding hairs and a slen­ der apical bristle dorsally, posteriorly Postero-Iateral corners of meso­ WIth 4-6 short spines and anteriorly notum not curved distinctly cau­ with 3-4 slender spines; hind tibia dad ; hind tibial comb of a single with 10-11 moveable spmes dorsally, spine; hind tibia with 2-3 long these all of similar size. hairs posteriorly. . . first instar THIRD INSTAR (Figs. 13-14) : pala with 3. Hind tibial comb with 4 spine~; 14-17 lower palmar bris tles; fore fe­ long hair covering on mid-line of mur with 6-8 spines anteriorly; hind mesonotum not reaching posterior femur with 4 short bristles dorsally, margin; fore wing buds overlap­ 5-8 short spines posteriorly and 4-5 ping less than h alf of the hind short spines anteriorly; hind tibia wing buds; fore wing buds not dorsally wi th 12-16 moveable spines, reaching base of a bdomen...... third ins tar the basal 1-4 shorter than rest. - Hind tibi.al comb with 6 or 8 FOURTH INSTAR: pal a with 18-19 lower spines; 1m'?; hair covering on mid­ palmar bristles; fore femur with 13- line of m psonotum reaching pos­ 14 spines antpriorly; hind femur with terior margin; fore wing buds 4 short bristles dorsally, 7-11 short overlapping more than h alf of spines posteriorly and a row of 4-5 hind wing buds; fore wing buds short spines anteriorly; hind femur reaching base of abdomen. . . 4. antero-ventrally with 4-5 short spines at base of subapical tuft of hairs ' 4. Hind tibial comb with 6 spines; hind tibia dorsally with 14-16 wing buds not completely o\'erla p­ move~ able spines, the basal 2-4 shorter than ping but reaching second abdom­ rest and often paired. inal segment; fore wing buds reaching but not surpassing base FIFTH INSTAR (Figs. 7, 15-16): pala of abdomen. . . . fourth instal' with 18-20 lower palmar bristles; fore Hind tibial comb with 8 spine.'>; femur with 16-22 spines anteriorly; wing buds completely overlapping hmd femur with 4 short bristles dor­ and reaching third a bdominal seg­ sally, 12-26 posteriorly and 3-7 ante­ mpnt; fore wing buds surpassing riorly ; hind temur antero-ventrally base of abdomen. . . fifth instal' wi"h 4-7 short spines at base of sub­ apical tuft of hairs; hind tibia dorsal­ (4) Description of larvae of C. bifida ly with 15-19 moveable spines, the Table I summarizes the most im­ basal 3-5 being shorter than rest and portant characters of the larvae of usually paired. 36 JOU BS ,\L EST()~I(" .. S(w. BBIT. COI.l·MBlA, VOL. 63 (1966), DEC. I, 1966

3

5

Figs 2 - 10-2, First instar larva C. bifida; 3, First instar larva C. expleta; 4, Anterior view of pala of first instar C. bifida; 5, Anterior view of pala of first instar C. expleta; 6, Dorsal view of meso and metanotum of fifth instar C. bifida; 7, Posterior view of pala of fifth instar C. bifida; 8, Posterior view of pala of fifth instar C. expleta; 9, An­ terior view of apex of pala of fourth instar C. bifida; 10, Anterior view of apex of pala of fourth instar C. expleta. [Drawings not to same scale.) JO{ · H S .\L ECCT()\I OI.. So .. . BHIT. ('(lI.!; ,III'U. \'01.. 6~ (1966), D~:c. 1. 1966 37

17

I / ! 12 18

, , ,,, ,

19

14

/ , f t ,~, ( "' ,. ' - :;- •f ~I 16 22

Figs. 11 - 22- Hind femur of larval in stars. 11·16, C. bifida; 17·22, C. expleta: odd numbers posterior viel\'. even numbers anterior vic\\'. 11 - 12, First instar C. bifida; 13 - 14, Third inst,11' C. bifida; 15 , 16, Fifth instal' C. bifida. 17 - 18, First instal' C. p.xpleta; 19 - 20, Third instal' C. expleta; 21 - 22 , Third in stal' C. expleta. [Drawings not to same scale.l C~ 00

Table 1. St ru ctural characteri st ics of larva l ins tars of C. bif ida and

c. expleta LA _ length from ante ri or of mesonotum to end of abdomen ; measur ements a re the mean of 10 in sects ; spine counts the range of

10 insects . <-. 0 d ;; Spines /. Sp i nes on Oi1 hind -- Lowe r pa l mar fore femur tibia hea d Length Abdomen l"J ~£_ecies_Instar bristles Anterior Ventral Anterior !"osterior Dorsal width (LA) width /! -- - - - c .... bifida 1 12 0 10 0 . 75mm. 1.1 5mm. 0 . 90 mm. 4 3 4 '=' Ul 2 14 4- 5 0 3- 4 4- 6 10- 11 1. 00 1. 70 1. 33 52 3 14- 17 6- 8 0 4- 5 5-8 12--16 1. 40 2 . 65 1. 65 to ~

Lf 18-19 13 - 11+ 1+-5 7- 11 I1f - 16 2. 20 n 4- 5 1. 7 5 3 . 35 c r r 5 18- 20 16- 22 4- 7 3- 7 12- 26 15 - 19 2. 25 5. 20 2. 45 '""" 2:;. expleta 1 10- 11 4 0 3 4 10 0 . 75 1.30 0 . 93 .q 2 11 4 0 5 5 12 1. 00 1.9 5 1.15 '=' 0> C-O

3 11- 12 4- 6 0 3- 5 4-5 13 - 14 1.30 2. 65 1.60 .... <0 0> 11- 12 9- 13 3- 6 3- 6 14- 17 1. 65 1+. 00 1. 35 0> 4 3- 4 -~ t::1 5 11-12 14- 27 3- 7 2- 4 4- 6 1 5- 17 2. 15 5. 60 2. 40 M co :-' .... <0 0> 0> JO UR:\,AL E:'>TOMOL. SoC'. BIUT. C()I.I · ~ IBIA , VOl,. 6:) (1966), DFoC' . 1, 1966 39

(5) Descriptions of larvae of C. ex­ Table II-Duration of larval instars of pleta Cenocorixa bifida in White Lake water, at 20"C and fed every other day on Artemia The descriptions below follow the salina. plan used for C. bifida above. Table I Instar Duration summarizes the main taxonomic First 4 - 5 days Second 4·5 characters. Third 4-5 FIRST INS TAR (Figs. 3, 5, 17-18): pala. Fourth 5-7 with 10-11 lower palmar bristles; fore Fifth 6-9 femur with 4 spines anteriorly; hinJ Total 23 - 31 femur with 6 long hairs dorsally, 4 short spines posteriorly and 3 slender spines anteriorly; hind tlbia dorsally laid in White Lake water and at tem­ with 10 moveable spines. peratures of 10 °C and 20 -' C. The dura­ SECOND INSTAR: pala with 11 lower tion of the larval instars at 20"C has palmar bristles; fore femur with 4 also been measured (Table II). spines anteriorly; hind femur with 5 long outstanding hairs a nd a pre­ At 20 °C the eggs too]\: 7-9 days to apical bristle dorsally, 5 short spines hatch, while at 10 c C they took 44-46 posteriorly and 5 short spines ante­ days to hatch. The larval period at riorly; hind tibia dorsally with 12 20 c C took 23-31 days. moveable spines. THIRD INSTAR (Figs. 19-20) : pala with DISCUSSION 11-12 lower palmar bristles; fore fe­ Hungerford (1948) has given a mur with 4- 6 spines anteriorly; hind figure (p. 13) of the various shapes of femur with 4 short bristles dorsally, eggs in the Corixidae. Both the shape 4-5 short spines posteriorly, 3-5 short spines a nteriorly; hind tibia with 13- of the egg and the mode of attach­ 14 moveable spines dorsally, the basal ment to the substrate is variable. 3 shorter than rest. While in the Micronectinae the eggs FOURTH INSTAR: pala with 11-12 lower are elongate a nd attached longitud­ palmar bristles; fore femur with 9-13 inally to the substrate without a spe­ spines anteriorly; hind femur with 4 cial attachment disc, those of the Co­ short bristles dorsally, 3-6 short spines posteriorly and 3-4 short spines rixinae are characteristically top­ anteriorly; h .nd femur a ntero-ven­ shaped with a button-like attachment trally with 3··6 short spines at base disc, borne at the end of a stalk of of subapical tuft of hairs; hind t ibia varying length . The chorion is also with 14-17 moveable spines dorsally, variable in surface texture, being the basal 3-5 shorter th an rest. smooth or with surface projections. FIFTH INSTAR (Figs. 8, 21-22): pala The eggs of Cenocorixa <1re thus typ­ with 11-12 lower palmar bristles; fore ical of the subfamily . femur with 14-27 spines anter io rly; Cobben & Pillot (1960) have con­ hind femur with 4 short bristles dor­ sidered t h e characteristics of impor­ sally, 4-6 short spines posteriorly a nd tance in the identification of the fifth 2-4 short spines anteriorly; hind fe­ instar larvae of Micronecta, Cymatia, mur a ntero-ventrally with 3-7 short Corixa, Hesperocorixa, Glaenocorixa, spines at base of subapical tuft of Sigara, Arctocorixa and Callicorixa. h a irs; hind tibia dorsally with 15-17 I can find no description of the lar­ moveable spines, th e basal 4-5 shorter vae of Cenocorixa in the present lit­ than rest and often paired. erature. It is evident that the latter (6) Duration of immature stages. ins tars of Cenocorixa are very similar The duration of the embryonic to those of the genera Sigara, Arcto­ development of C. bifida from White corixa and Callicorixa in the pubes­ Lake has been determined for eggs cence on the mesonotum. 40 JOURNAL ENTOMOL. SOC. BRIT. COLUMBIA, VOL. 63 (1966), DEC. I, 1966

The character of the apical spine The duration of the immature of the pala and the prominence at stages in C. bifida at 20°C and fed on the base of the apical lower palmar Artemia salina every other day, is 23- bristle serves to separate larvae of 31 days. Since it is possible to length­ C. bifid a from those of C. expleta. The en the egg from 7-9 days at 20°C to larval instars are also easy to key out 44-46 days at l00C, it seems likely in each species. tha t the larval ins tars would also take The study of Cenocorixa suggests much longer to develop at lower tem­ that it should be possible to key out peratures, and so the life cycle at dif­ the last three larval ins tars of most ferent times of year would not occupy Corixid species, since the characters the same developmental time period. of the fifth instar are usually also Griffith (1944) reports 35 days as the found in the third and fourth instar. developmental time for Ramphocorixa However, the first two instars lack acuminata (Uhler) and 36 days for many of these essentifll characters, Corisella edulis (Champion), but and may prove extremely difficult to notes a great variation in rearing ex­ identify when a mixture of species periments. These differences could occur together. have been due to different feeding The great transformation between rates and/ or different temperatures: the second and third ins tar larvae in no temperature data are given in the Cenocorixa, also occurs in other Co­ paper. rixidae, for example Palmocorixa buenoi Abbott (Hungerford, 1919). Acknowledgements Not only does this involve the exter­ This research was carried out while nal characters cited, but there is also in receipt of grants from the National Re­ great changes in the internal anat­ search Council of Canada and the Univer­ omy at this time. sity of British Columbia.

References Cobben, R. H. , and Pillot, H. M., 1960. The larvae of Corixidae and an attempt to key the last larval instar of the Dutch species (Hem., Heteroptera). Hydrobiologia 16:323-356. Griffith, M. E., 1945. The e nvironment, life history and structure of the water boat­ man, Ramphocorixa acuminata (Uhler) (Hemiptera, Corixidae). Univ. Kansas Sci. Bull. 30:241-365. Hungerford, H. B., 1919. The biology and ecology of aquatic and semiaquatic Hemip­ tera, Ibid. 11:1-328. Hungerford, H. B. , 1948. The Corixidae of the Western Hemisphere (Hemiptera). Ibid. 32:5-827. Lansbury, I., 1960. The Corixidae (Hemiptera-Heteroptera) of British Columbia. Proc. Ent. Soc. B.C. 57:34-43.

A BRITISH COLUMBIA RECORD FOR Xenos peckii KIRBY A male Polistes tuscatus variatus tween the sterna of the same seg­ Cresson parasitized by Xenos peckii ments. The wasp and the parasites Kirby was among various wasps col­ were identified in 1958 by Dr. R. . M. lected August 5, 1947 after they had Bohart, University of California, settled for the night on mullein, Ver­ Davis, Calif. One of the parasites is bascum thapsus L., 2 miles south of in the collection of the University of Vernon, B.C. The parasitized wasp British Columbia, Vancouver, B.C. had two male strepsipteran pupae protruding from its abdomen, one lat­ HUGH B. LEECH, erally from between the 5th and 6th Calif. Academy of Sciences, terga, the other ventrally from be- San Francisco, Calif.