BULLETIN DE L'INSTITUT ROYAL DES SCIENCES NATURELLES DE BELGIQUE ENTOMOLOGIE, 67: 45-55, 1997 BULLETIN VAN HET KONINKLIJK BELGISCH lNSTITUUT VOOR NATUURWETENSCHAPPEN ENTOMOLOGIE, 67: 45-55, 1997 Morphology and Chaetotaxy of Larval Hydraenidae (Coleoptera) II: The Subgenus Ochthebius s. str. Leach by Juan A. DELGADO & Agustin G. SOLER Abstract different subgenera of Ochthebius was thought to be of interest. The morphology and chaetotaxy of the three larval instars of the The aim of this study is to describe the morphology and subgenus Ochthebius (s. str.) of the genus Ochthebius LEACH chaetotaxal pattern of the larvae of the subgenus Ochthe are described and illustrated following the setal pattern of bius (s. str.) and to provide illustrations to facilitate the Ochthebius auropallens F AIRMAJRE. The study revealed many identification of all these characters. The present work, features on the head capsule, cephalic appendages, and the we hope, will be useful in offering new features for thoracic and abdominal segments that may be useful for sys correctly defining the diagnostic characters of the tematic and phylogenetic comparisons. genus Ochthebius. Moreover, this work will serve as a reference for intended future papers which will discuss Key-words: Coleoptera, Hydraenidae, Ochthebius, larvae, chaetotaxy. the real position of some lineages of this genus on the basis of preimaginal characters (DELGADO & SOLER, in press a). Resume Material and methods La morphologie et Ia chetotaxie des trois stades larvaires du sous-genre Ochthebius (s. str.) sont decrites et caracterisees Material examined. - The larvae used in this study sur Ia base des caracteres larvaires de l'espece Ochthebius auropallens FAJRMAIRE. L'analyse chetotaxique de Ia capsule were obtained by rearing in the laboratory the adults cephalique, des pieces buccales, des pattes et des segments of several species of Ochthebius belonging to different thoraciques et abdominaux, s'est averee d'une grande utilite subgenera. The rearing techniques used by us and the pour les comparaisons taxonomiques et phylogenetiques. biology of this genus will be published in a separate paper. Some specimens found ex societate imaginis Mots cles: Coleoptera, Hydraenidae, Ochthebius, larves, che were also studied. The present work is based on the study totaxie. of the three larval instars of Ochthebius auropallens F AIRMAIRE whose morphology is very similar to those other species of the subgenus Ochthebius (s. str.) studied Introduction by us. Larval study.- The description of immature Ochthebius Ochthebius LEACH is one of the most diverse and hetero is based on material cleared, glycerolated and mounted geneous genera within the family Hydraenidae. The on standard glass slides. The technique for studying phylogenetic relationships among the different lineages larvae in glycerol has been described by BousQUET & currently included in Ochthebius have not been studied GOULET (1984). For general studies under an optical in much detail. In fact, HANSEN (1991) in his excellent microscope, the specimens were placed on a ringed slide revision of the different genera of Hydraenidae filled with glycerine. The parts of the body to be exam observed several plesiomorphies among the diagnostic ined under high magnification were detached and posi characters of Ochthebius and suggested that this tioned on a slide with Hoyer's mounting medium and genus is a paraphyletic group. Recent studies on larval covered with a coverslip. Drawings were prepared using a morphology in Coleoptera (ASHE, 1986; ALARJE, 1991, microscope with a drawing miiTor. When possible, at 1995; BEUTEL, 1994; BOUSQUET & GOULET, 1984; DEL least six specimens were used to describe each character. GADO & SOLER, in press a) have revealed the value The system for naming setae and pores used in the present of this kind of work for phylogenetic analysis. For article follows that employed by DELGADO & SOLER this reason, a study of the larval morphology of the (1997). '' 46 Juan A. DELGADO & Agustin G. SOLER :: oE.d 1 ; ··. .. Ed2 : 0 EC2 0E12 O ~~ CG2 P1 0 P2 0 P3 ~-o~o~P~4~----_,~--------~~~ 1 2 Figures 1-2. - Ochthebius auropallens, larval instar I, head. I, dorsal view. 2, lateral view. CG: cephalic glands; Cl, clipeal setae; EC: epicranial campaniform sensilla; Ed, epicranial dorsal setae; El, epicranial lateral setae; Em, epicranial marginal setae; FC, Frontal campaniform sensilla; Fd, frontal discal setae; Fl, frontal lateral setae; Fm, frontal marginal setae; L, lateral setae; T, temporal setae; V, ventral setae. Scale= 0.1 mm. II Morphology and Chaetotaxy of Larval Hydraenidae (Coleoptera) II 47 Results sensilla are present: C1-C5. One pair of tergal gland is present in the disc of the pronotum. Mesonotum as in Description of the larva of Ochthebius auropallens FAIR Fig. I 0; rows A with 4 minute setae; rows L with 3 setae: MAIRE (Figs 1-20). Ll-L3; rows P with 4 setae: Pl-P4;·rows Da, Db and De each with I setae: Da 1, Db 1 and De 1, respectively. Instar I Dal and Del frequently with apex pectinate. Campani form sensilla Cl and C2 absent. Two pairs of tergal Total body length about 1.4 mm. Head: head capsule glands are present in the mesonotum. Metanoh1m similar width: 0.21 ± 0.01 mm (Mean ± SD; n = 6). Ecdysial to mesonotum. Prosternum as in Fig. 11; presternum sutures Y -shaped. Ocular areas with 5 stemmata. Chae divided into 2 lateral regions, each with 2 setae; euster totaxy as follows and in Fig. 1 and 2. Frontal region (in num consisting of central sclerotized area with 1 pair of each lateral half) with 2 campaniform sensilla and 5 setae; sternum indistinctly sclerotized and with 1 pair of setae arranged in 3 rows: 2 frontal dorsal setae, 2 frontal setae. Laterosternum fused to prehypopleuron fanning lateral setae and 1 frontal marginal seta. Epicranial re a sclerotized lobe anterior to coxa, with 3 setae. Post gions with 2 campaniforrn sensilla, 2 epicranial glands hypopleuron consisting of slightly sclerotized lobe pos and 10 setae arranged in 4 rows: 4 minute posterior terolaterad to coxa, with associated denticles or minute setae, 2 epicranial dorsal setae, 2 epicranial lateral setae spines. Mesosternum (Fig. 11) differs from prosternum and 2 epicranial marginal setae. Temporal regions with 4 as follows: sternum with 2 pairs of setae; presternal setae: Tl-T4. Lateral regions with I campaniforrn sensil region with only I seta and prehypopleuron with 2 setae. lum and 2 setae: Ll and L2. Ventral region (in each Mesothoracic spiracles present, annular and associated lateral half) with 2 short setae: Vl and V2. Frontal to 1 seta. Metasternum similar to mesosternum. Meta region with 2 sclerotized, serrate and well developed thoracic spiracles vestigial, without setae. Legs: Pro egg-bursters and two small teeth behind these. Labrum thoracic leg as in Fig. 12. Coxa with 1 campaniform (Fig. 3) markedly produced anteromedially, with 2 cam sensillum and 15 setae: 1 D, 2 Ad, 4 AI, 1 Av, 2 Pd, 4 paniform sensilla and 7 setae arranged in 2 rows in PI and lPv. Trochanter with 7 campaniform sensilla each lateral half: 2 labral dorsal setae and 5 labral and 8 setae: I Ad, 2 AI, 2 Av, 1 PI, 1 Pv and 1 V. marginal setae. Lm I, Lm3 and Lm5 arise dorsa laterally, Femur with 2 campaniforrn sensilla and 8 setae: 1 D, Lm2 and Lm4 arise ventrolaterally (Fig. 4). Lm4 is a I Ad, lAI, 2 Av, I Pd, 1 PI and 1 V. Tibia with 1 long seta and Lm2 is pectinate. Antenna (Fig. 5) with campaniform sensillum and 9 setae: 2 D, 1 Ad, 1 AI, 1 article I short and with 4 campaniform sensilla around Av, 2 Pd, 1 PI and 1 Pv. Tarsungulus with 2 minute the apex, without setae; article II about 3.9x as long as setae. article I; article III about 0.8x as long as II. Article II with 4 long setae and 2 solenidia, one of which may be Abdomen: Tergum I as in Fig. 13. Seta P2 absent; considered as a sensory appendage. Article III with 4 setae Db! and Del absent; campanifonn sensillum C4 setae and 3 apical solenidia; IIS3 short. Mandibles absent. Directly below the posterolateral region oftergum (Fig. 6) right and left nearly identical in size and shape; I there is a pair of lateral sclerites or pleurites. The with 2 campaniform sensilla and 2 setae. Ml long and M2 dorsopleural sclerite is located between the tergum I of medium length. Prostheca curved and slender; molar and the ventropleural sclerite. One spiracle and 2 setae area well developed. Maxilla as in Fig. 7. Carda triangu are on this sclerite. The ventropleural sclerite is located lar, with 1 seta. Stipes with 4 setae and 1 campaniform between the sternum I and the dorsopleural sclerite. Only sensillum. Lacinia not fimbriate, with 6 developed and 1 seta is on this sclerite. Sternum I as in Fig. 14. Posterior stout setae. Palpifer consisting of crescentic sclerite at row with 2 setae, although near P2 there is a distinct scar base of maxillary palpus; with 1 seta. Maxillary palpus that might indicate the presence of a miscarried seta. with 3 articles; article II 1.25x as long as article I, article Abdominal terga II-VIII similar to tergum I. Differs III 1.5x as long as article I. Apical article with con mainly by the progressive loss of setae A. Abdominal spicuous, basal, digitiform, sensory appendage on exter terga VI to VIII only with AI. Dorsopleural and ventra nal surface; article I with 2 campaniform sensilla, article pleural sclerites of the abdominal segments II to VIII each II with 2 setae and 1 campaniforrn sensillum. Labium as with 2 setae. Abdominal sterna II-VIII similar to sternum in Fig. 8, consisting of 3 sclerites; ligula short and broad, I except for the addition of seta D2 (Fig. 14). Setal bearing 4 papillae; palps with 2 articles, article I with I homologies on segments IX and X are difficult to estab campaniform sensillum on mesial margin. Submentum lish. Tergum IX as in Figs. 15 and 16, with 4 pairs of setae with 1 pair of setae; mentum with 2 pairs of setae and I and 1 pair of pretergal glands; no spiracles detectable. pair of campanifonn sensilla. Prementum with 2 pairs of Urogomphus as in Fig. I 7, long, with 2 articles; basal setae. article (URI) not fused to tergum IX, with 6 setae and 4 pores or campaniform sensilla. Article II (URII) short and Thorax: Pronotum as in Fig. 9. Rows A with 4 setae: Al slender, 0.45x as long as article I. URII with a long seta: A4; rows L with 3 setae: Ll-L3; rows P with 4 setae: Pl AE, arising from apex. Abdominal segment X as in P4; rows Da with 1 seta: Dal; rows Db with 1 seta: Dbl; Fig. I 5 and I 6. Anal vesicle or pygopod bearing a pair rows De with 1 seta: Del. Five pairs of campaniform of stout hooks, and a slightly sci erotized area with 3 pairs '' 48 Juan A. DELGADO & Agustin G. SOLER 7 6 I I Morphology and Chaetotaxy of Larval Hydraenidae (Coleoptera) II 49 ,.,__,__~' _):::::- ~·:· C\ () ] r, :--:--...,... oA·4 ...... ~·~· ............... ~·~·"· ~ ~ ·~ A1 . . ,., ... 0 0 C2 ~.:· Tg --.. ~:·~ ~~ .. A ~':. L 1 ' ~- Dc1 Db1 Oa1 ''· Y.. _-.... \_ : __ --•lt =:==--- ~:~' ,~ ·~- ~ ~,1 :_=.. ~~ c 0 ~c.o,~ _• ., /1 ... ~ - ~ J_ o .. - -"b·3 ....._,....c...~... . ,....,.......- c...s5. . . . , _: - . J >-c_o~ :s~z ,, ._ 9 10 Figures 9-10. - Ochthebius auropallens, larval ins tar I. 9, pronotum. 10, mesonotum. A, anterior setae, C, campaniform sensilla; Da, Db and De, discal setae; L, lateral setae; P, posterior setae; PG, pretergal gland. Scale= 0.1 mm. +- Figures 3-8. - Ochthebius auropallens, larval instar I. 3, labnun, dorsal view. 4, epypharinx. 5, antenna, dorsal view. 6, mandible, dorsal view. 7, maxilla, ventral view. 8, labium, ventral view. C, campaniform sensilla; La, lacinial setae; Ld, labral dorsal setae; Lg, ligula; Lm, labral marginal setae; M, mandibular setae; Mnt, mentum; Pf, palpiferal setae; Pm, palp al setae; Pmnt, prementum; SD, sensorial digitif orm appendage; Smnt, submentum; Stp, setae of the stipes; IIS ( 1-3), antenna! solenidia of atiicle 11; IIIS ( 1-3), antenna! solenidia of article IlL Scale= 0.05 mm. I I 50 Juan A. DELGADO & Agustin G. SOLER 11 Figure 11. - Ochthebius auropallens, larval instar I. Prosternum and mesosternum. CX, coxal cavity; Eu, eustemal setae; Pr, presternal setae; Prehy, prehypopleural setae; Pohy, posthypopleural setae; S, spiracular setae, Sp, siracle; St, sternal setae. Scale: 0.1 mm. of small setae and 1 pair of campaniform sensilla. The of the dorsopleural and ventropleural sclerites in the central pair of setae slightly more developed than the abdomen. These sclerotized areas are distinct and not others. fused with the tergal or sternal abdominal regions. Dorsopleural sclerites with 3 setae: DP 1, DP2 and a Instar II new subprimary setae, DP' (Fig. 19). Abdominal sterna II-VIII with 2 pairs of new discal (subprimary) seta: Total body length about 1.9 mm. Head capsule width: D' and D". 0.27 ± 0.01 (Mean ± SD; n = 6). Differs from instar I by absence of the egg-bursters in the head. Chaetotaxy lnstar III similar to instar III and characterized by the addition of subprimary setae. Pronotum as in Fig. 18, with 6 pairs Total body length about 2.6 mm. Head capsule width: of new discal (subprimary) setae: Da', Da", Db', Db", 0.35 ± 0.0 l (Mean ± SD; n = 6). with following differ De' and De". Differs from third ins tar by the presence ences to ins tar II: Abdominal terga I-VIII, in each II Morphology and Chaetotaxy of Larval Hydraenidae (Coleoptera) II 51 · ""t·P13 Pdc~·.::::::::::::.::::. ==' ·:· cl Al4r/ .... :::/} P12 .·.·: v,. 12 Figure 12. - Ochthebius auropallens, larval instar I. proleg, anterior view. Ad, anterodorsal setae; AI, anterolateral setae; Av, anteroventral setae; C, campaniform sensilla; D, dorsal setae; Pd, posterodorsal setae; PI, posterolateral setae; Pv, posteroventral setae; V, ventral setae. Scale = 0.1 mm. lateral half, with 3 additional lateral setae (Fig. 20). We because, at the present level of knowledge, a representa interpret the 3 new setae as DPI, DP2 and DP' located in tive model cannot be selected within their different sub the dorsolateral sclerite of instar II. The loss of dorsolat genera. eral sclerites in instar III is clearly connected with the The larval morphology descrived in 0. auropallens is appearance of spiracles and setae DP1, DP2 and DP' very similar in other studied larvae belonging to the attached to tergal region of the abdomen. Abdominal subgenus Ochthebius. Specific variations with respect sternum I, in each lateral half, with 1 additional lateral to the described characters mainly affect the shape of seta. We interpret this seta as VPI of instar I and II. egg-bursters, the size and shape of the articles of Abdominal sterna II-VIII, in each lateral half, with 2 the urogomphi and head appendages and the size and additional lateral setae: the setae VPI and VP2 of shape of the setae. The presence of cephalic egg-bmsters instar II. in the first instar larvae of Hydrophiloidea (sensu In some examined species of Ochthebius (s. str.) more CROWSON, 1955) has been considered by BEUTEL (1994) variability was observed. We have found several cases of as a possible autapomorphy of this superfamily as well as secondary setae in instars II and III. a groundplan feature ofHydraenidae. However, this char acter is present in all the lineages of the subfamily Ochthebiinae studied by us (see DELGADO & SOLER, in Discussion press a and b), but not in the subfamily Hydraeninae (DELGADO & SOLER, 1996; DELGADO & SOLER, 1997; In this paper we have studied the morphology and chae DELGADO et al., in press). In contrast with BEUTEL totaxal pattern of the three larval instar of the subgenus (1994) we consider the presence of cephalic egg-bursters Ochthebius (s. str.) ofthe genus Ochthebius. We decided in Hydraenidae not as a groundplan of this family but as to study the larval morphology and chaetotaxy of the an autapomorphy of the derived subfamily Ochthebiinae. different subgenera of Ochthebius in separate works In this sense, the presence of egg-bursters in some larvae I I 52 Juan A. DELGADO & Agustin G. SOLER 0~0 o A2 ···•·· ..... A> . DP2 o 0 A1 .-- :.:·. C) Da1 SP 13 . .J . ·,.: . Ps1 VP1(\ VP2"zj 14 Figures 13-14. - Ochthebius auropallens, larval ins tar I. 13, abdominal tergum I. 14, abdominal sterna I and II. A, anterior setae; C, campaniform sensilla; L, lateral setae; P, posterior setae; Ps, presternal setae; D, sternal discal setae; Da, discal setae; DP, dorsopleural setae; Sp, spiracle; VP, ventropleural setae. Scale = 0.1 mm. ---j Figures 15-17. - Ochthebius auropallens, larval instar I. Segments lX and X. 15, dorsal view. 16, lateral view. 17, urogomphus. A, anterior setae; AE, apical stilus; C, campaniform sensilla; U, urogomphal setae of article I; URI, urogomphal basal article; URJI, urogomphal apical article; ?, uncoded setae. Scales= 0.1 nun. I I Morphology and Chaetotaxy of Larval Hydraenidae (Coleoptera) II 53 · 16 54 Juan A. DELGADO & Agustin G. SOLER 0·········· 0 .................... ~~"21'~1 A4 A3 Db' Q Da' 18 a A3 a A2 '.'·. ·. ... _ ;,: . •' .~ 0 A1 '~.: Tg 0 Da1 O L2 L3 <.) P4 -~ ~3 ocso -- -------- P1 20