Bull. Kitakyushu Mus. Nat. Hist., 3: 27-39. December 31, 1981

On the mechanism of copulation in Hepialid , Endoclita excrescens (Butler) and Hepialus fusconebulosa (De Geer) (: )

Kyoichiro Ueda

Kitakyushu Museum of Natural History, Nishihonmachi,Kitakyushu, 805 . (Received on 20. Sept., 1981)

Abstract The male and female genitalia of Endoclita excrescens (Butler) and Hepialus fusconebulosa (De Geer) are described and figured. The musculature of male genitalia of Endoclita excrescens (Butler) is described and figured. The mode of firm connection between male and female genitalia, which has not been recorded in Lepidoptera, is effected in the following sequences: (1) the mesosome was in serted into the dorsal groove of central process (E. excrescens) or grappled the dorsal sclerotized portion of central process (H. fusconebulosa), (2) the valvellae were applied to the lateral walls ofseminal gutter (E. excrescens) or the depression ofsubanal plate (H.fusconebulosa), which was opened by the inflation oftegumen, (3) thevalvae clasped the weakly sclerotized portions of female diaphragma (E. excrescens) or lateral portions of female ninth tergum and sternum (H. fusconebulosa). The characteristics of these copulation mechanism in Hepialidae and their phylogenetic significance are shortly discussed.

Introduction The male and female genitalia ofLepidoptera are much variable in structure. They have been carefully studied in detail and used as important characters in taxonomy. On the contrary, the function of parts of the genitalia, especially in copula, has almost been remained unknown with the exception of De Jong (1978) and other few works. In the family Hepialidae, such studies are few and we hardly find Stekol'nikov's remark that "The nature of fixation of the sexes in copulation is quite different in H. humuli from what has been observed in the other Lepidoptera. The dorsal and ventral tegminal lobes open and are inserted in special depressions on the abdomen of the female, and the valves hold the abdomen of the female laterally. The weight during copulation is therefore principally borne by the tegminal lobes and the muscles responsible for move ment of the lobes are most strongly developed" (Stekol'nikov, 1967: 403-404.). From 1979 to 1980,1 could make several pairs of Endoclita excrescens (Butler) in copula by hand-pairing method (Fig. 1). The male and female in copula were 28 Kyoichiro Ueda

fixed in boiling Carnoy fluid, then dissected and observed in detail. In addition to them, I had an opportunity to examine a pair of Hepialusfusconebulosa (De Geer) in copula, which was fixed in Bouin fluid, through the courtesy of Dr. Kauri Mikkola, University of Helsinki, Finland and I could make a comparison between the two species. The terms used in this paper for each structure are based on Ueda (1978, 1980).

1. Description of male and female external genitalia. Fig. 1. A pair in copula. Arrow indicates 1.1. Endoclita excrescens the fore and mid legs of male. Upper; (Butler)*" female, lower; male. Male external genitalia: Tegumcn very large with dorsal margin bearing a pair of swollen portions, which bears dense small serrations; twin process almost reduced; processus momenti broad and hook-shaped, strongly bent downwards at middle, and its posterior portion producing dorsally; valvclla long, producing ventrally, and tapering towards tip; the dorsal margin of valvclla with dense denticulations, and producing laterally; vinculum almost as deep as tegumcn, with no special process on the posterior margin; saccus large and rounded. Valva small, tapering towards apex and with rounded tip. Mesosomc fused with tabulatum near its base, strongly sclerotized ventrally and ending in a sharply pointed tip. Tabulatum strongly concaved at middle portion and with a large keel-like ridge running through its ventromedial portion (muscle attachment of m.7). Female external genitalia (Fig. 2): Eighth sternum well sclerotized, almost rectangular. Ninth tergum almost three limes as deep as ninth sternum, slender and semicircular, with minute hairs on dorsal margin. Ninth sternum producing a pair of slender and flat processes from lateral margins; ventromedial portion of the sternum forming central process which has a slender and deep groove on its dorsal surface. Diaphragma very broad, with a seminal gutter running middle of diaphragma. Weakly sclerotized subanal plate on lateral portion of dia-

*1) The external genitalia of this species were figured on Ueda, 1978 and 1980 (male; Figs. 8 A-C, Ueda 1979, female; Figs. 11-12, Ueda 1980). Copulation mechanism in Hcpialid moths 29

Dorsal groove Seminal gutter

Central process

Lateral process

Fig. 2. Female ninth sternum of E. excrescens (Butler). Right dorsolateral aspect. phragma, and almost elliptical. 1.2. Hepialus fusconebulosa (De Geer)*2> Male external genitalia: Tegumen broad; twin process small, with rounded tip; processus momenti strongly bent downwards at middle and dilating towards distal margin; valvella bifurcate, the dorsal process of valvella short and triangu lar, the ventral processof valvella slender, projecting ventrally and its tip reached near ventral margin of vinculum; vinculum broad, with a pair of slender processes on lateral posterior margins; saccus large, ventromedial portion of saccus with acute irregular apodemal processes on dorsal wall (muscle attachment of m.78). Valva rather long, three times as long as wide, almost subequal in width throughout the length, tapering slightly on distal margin and projecting above beyond dorsal margin of tegumen; the ventral margin of valva slightly produced posteriorly at middle and its tip truncate. Mesosome large and well sclerotized. Tabulatum almost rectangle, with small serrations on internal surface. Female external genitalia (Figs. 3-4): Anterior portion of eighth sternum weakly sclerotized. Posterior margin of ninth tergum weakly concaved at middle;

*2) Male external genitalia of this species was figured on Ueda, 1978 (Figs. 7 A-C). n

Fig. 3. Hepialus fusconebulosa (De Geer). Terminal Fig. 4. Hepialus fusconebulosa (De Geer). Female genitalia. Caudal segments of female abdomen. Lateral aspect (left). aspect. Copulation mechanism in Hepialid moths 31 dorsomedial portion of ninth tergum membranous. Ninth sternum three times as wide as high; ventromedial portion weakly swollen with slight depressions on both sides; dorsal margin of ninth sternum with a pair of short and blunt processes, which obliquely protrudes upwards. Subanal plate very slender and weakly sclerotized.

2. Musculature of male external genitalia of Endoclita excrescens (Butler) (Figs. 5-8) The musculature system is mainly based on Birket-Smith (1974). m.12 (tegumen-twin process): untraceable, the absence of this muscle seems to

m.i9-1

m.i9-2 m.i9-

Fig. 5. Endoclita excrescens (Butler). Male genitalia showing its musculature. Frontal aspect. 32 Kyoichiro Ueda

Fig. 6. Endoclita excrescens (Butler). Male genitalia showing its musculature. Lateral aspect (left). be correlated to the reduction of twin process. m.3 (tegumen-processus momenti): absent. m.4 (vinculum-processus momenti): a long and strong muscle, arising dorsally in lateral portion of vinculum-just laterally of the tabulatum in normal position- and inserted on the anterior margin of processus momenti. m.5 (vinculum-valva): thin and slender muscle, taking it origin on the middle of lateral portion of vinculum and inserted on dorsal portion of the base of valva. m.6 (tabulatum-valva): very thin muscle, arising on latero-frontal margin of tabulatum and inserted dorsally on the inner wall of the base of valva. m.7 (vinculum-ductus ejaculatorius): broad and thin muscle, arising on ventro- Copulation mechanism in Hepialid moths 33

Valva

Tabulatum

Vinculum

Fig. 7. Endoclita excrescens (Butler): Male genitalia; right valva and vinculum with their muscles. Lateral aspect.

m.i9 - 2

m.i9-3

Fig. 8. Diagram showing ductus ejaculatorius and its muscles of E. excrescens (Butler). frontal margin of vinculum, bent at an acute angle on anterior margin of tabu latum, and inserted on ventral portion of ductus ejaculatorius. m.8 (vinculum-tabulatum): very large and strong muscle, arising on ventral portion of vinculum and inserted on tabulatum. m.i9 (tegumen-tegumen, tegumen-ductus ejaculatorius, processus momenti-ductus ejaculatorius): extensively large muscle, divided into three parts: m.i9-l very large transverse muscle, which interconnects the subdorsal walls of tegumen. 34 Kyoichiro Ueda m.i9-2: rather small and short muscle, arising on the middle portion of tegumen and inserted on the dorsal wall of ductus ejaculatorius. m.i9-3: very large muscle, arising on the inner wall of processus momenti and inserted on lateral wall of ductus ejaculatorius, and ventral portion of this muscle passing below ductus ejaculatorius and interconnects the two processus momenti. m.10 (processus momenti-valvella): large and triangular muscle, arising on the bending portion of processus momenti and inserted on the membrane near the middle of valvella. m.11 (dorsal wall of sugenital crypt-valvella): absent.

3. The mechanism of copulation

3.1. Endoclita excrescens (Butler) (Figs. 9-10) First of all, the male was stimulated by rubbing the ventrocaudal portion of abdomen longitudinally, or gently pushing dorsal portion of tegumen. The male , which was fully stimulated, usually began to move his genitalia in the following sequences:*3) 1) the whole tegumen is turned upwards on the processus momenti (con traction of m.4),

Spermatophore

Valvella

Mesosome

Subanal plate(?)

Lateral process Fig. 9. Endoclita excrescens (Butler) in copula. Right; male, left; female.

*3) the inferred movement of muscle indicated in ( ). Copulation mechanism in Hrpialid moths 35

VIN

Fig. 10. Diagrams showing the movements of male and female genitalia before coupling in E. excrescens (Butler). Upper; tegumen in caudal aspect, lower; whole genitalia in lateral aspect (left). A; normal position. B: just before copulation.

2) mesosome raises at an angle of 45° to body axis and valvella takes almost horizontal position, 3) during l)-2), the whole tegumen furthermore opens laterally, and corresponding to this movement, valvaealso open laterally (contraction of m.i9-l and m.5), 4) tabulatum is shifted from normal horizontal position to almost upright one (relaxation of m.7), as a result of processes 1) to 4), tegumen is strongly inflated laterally in caudal view (Fig. 10, B) and mesosome protrudes posteriorly and it is completely exposed in lateral view, 5) tegumen, which was turned to almost horizontally, is quickly shifted in normal position, 6) simultaneously, the valvae are strongly closed, 7) lateral inflation of tegumen is turned to normal deflated condition, which is not correctly synchronized with the movements of 5) and 6), but late a little for them. When the male moth was fully stimulated, the movements of male genitalia from 1) to 7) could be observed repeatedly. In female, the scales around central process were removed to observe its dorsal groove clearly. The central process 36 Kyoichiro Ueda was pushed down a little, then the ostium was exposed. Pairing: At first, the tip of raised mesosome of male genitalia was inserted into the dorsal groove of central process of the female genitalia. The lateral margins of valvellae with small serrations were applied to the lateral walls of seminal gutter, which was opened by the inflation of tegumen. Then, the ostium was exposed and the tips of valvellae were inserted into the ostium. At the same time, the valvae clasped the weakly sclerotized portions of female diaphragma (subanal plate?). Therefore the female diaphragma was grasped by valvellae from the inside and by valvae from the outside, respectively. Ventrally, the eighth abdominal sternum of male was tightly applied to the ventral surface of female ninth abdominal sternum. Thus the female ninth abdominal sternum was tightly held by mesosome dorsally and male eighth abdominal sternum ventrally, respectively. The coupling of male and female external genitalia was completed through the processes mentioned above, then the transfer of spermatophore was began. Posture in copulation (Fig. 1): After the pair is made in copula by hand-paring method, female was dragging male, and hung in the air from the tip of twig or similar substratum. She held the pair with her strong fore and mid legs and took posture of repose in copulation. During copulation, male took a special posture stretching the fore and mid legs together almost at a right angle to body axis. Duration of copulation: Almost a day and night. At the dusk of the next evening, the male began to flatter his wings swiftly, ceased copulation and flew away from female rapidly. When the pair, which had been in coupulation during 15 hours, was put experimentally in the darkbox, the male also began to flatter his wings and ceased copulation. On this case, the spermatophore was not completely transferred into the bursa copulatorix of female and the posterior portion of spermatophore, which hung down from the ostium, could be observed. This spermatophore was entered into the bursa copulatorix by some movements of female abdomen. Number of spermatophore: Although the duration of copulation is extraordinarily long, only one spermatophore is transferred to the female during copulation. 3.2. Hepialus fusconebulosa (De Geer) (Fig. 11) The male and female genitalia of this species are basically same as those of the former species, but the following structural differences will be detected: 1) the enlargement of valvae, 2) the absence of groove on dorsal portion of central process, and 3) presence of subanal plates on the lateral sides of seminal gutter. In accordance with these structural differences, the copulation mecha nism of this species is modified in the following points: 1) the valvae clasp the lateral portions of female ninth tergum and sternum, 2) mesosome grapples Copulation mechanism in Hepialid moths 37

Processus momenti Tegumen / XVIll

Valvella

Mesosome

FemaleV -^^^fuiil Fig. 11. Hepialus fusconebulosa (De Geer) incopula. Right; male, left; female. dorsal sclerotized portion of central process, and 3) the tips of valvellae tightly hook the depression of subanal plates, and owing to opening of valvellae resulted by the inflation of tegumen the seminal gutter isopened laterally, then the ostium is exposed. However, these structural and functional differences do not seem to be essential in comparison with the former species. It is inferred that the subanal plate is also functioned as the cover of seminal gutter in normal condition. Judging from these functions of this plate, it is concluded that the plate does not closely relate to anus, and the term "lateral sclerite" of Common (1966) may be appropriate for this plate (Dr. Dugdale suggested similar interpretation of subanal plate and Common's term to me in personal communication).

4. Discussion — Characteristics of copulation mechanism in Hepi alidae and their phylogenetic significance. In comparison with general morphology of male and female genitalia of Ditrysia, the peculiarities of the genital structure in Hepialidae are summarized as follows: 1) absence ofuncus, 2) absence ofsclerotized aedeagus, 3) develop- 38 Kyoichiro Ueda ment of valvella, 4) development of mesosome, 5) presence of transverse muscle m.i9 in the male, 6) presence of seminal gutter, 7) presence of subanal plate, and 8) developments of various processes on ninth abdominal segments, like central process, lateral process, etc. in the female (Birket-Smith, 1974, Ueda, 1978, 1980). These structural peculiarities are well adapted for the mechanism of copulation mentioned above. The characteristics of the copulation mechanism are generally summarized in the following points: 1) the lateral opeing of tegumen and valvella, 2) the uncus-like function of mesosome on ventral portion of female genitalia (grappling the central process), 3) the grasping of diaphragma with valvellae and valvae, grappling of central process with mesosome, and exposure of ostium through the movements 1) and 2). These characteristics are apparently unique to the Hepialidae and have not been reported in the copulation mechanism of the other Lepidoptera. Moreover, these characteristics in structure seem to be also shared in common among the Hepialoid families, Prototheoridae (Janse, 1942), Palaeosetidae (Ueda, in preparation) and Anomosetidae (Kristensen, 1978b). However, it is very diffi cult to consider these character-states as "primitive" only on the basis of phylo- genetic position of Hepialidae in Lepidoptera. At first sight, for example, the absence of aedeagus seems to indicate the "primitive" character-state comparing to "the presence of aedeagus". But, taking the fact that as far as known all the members of Trichoptera — sister group of Lepidoptera have well sclerotized aedeagus into consideration, it is preferable to me that this character-state of Hepialidae is regarded as the secondary specialization. Therefore, these specialized character-states of male and female genitalia in Hepialidae and its allied groups are regarded as synapomorphies, which unite them into a monophyletic group. But, the process, in which such specialized structure and function were aquired in the course of Hepialid evolution is still remained unknown and the comprehensive study of the structure and function of the genitalia from various respects including hand-paring method will be ex pected for its allied groups.

Acknowledgements I wish to express my cordial thanks to Professor, Dr. Ryuzo Toriyama, Dr. Masamichi Ota, emeritus Professor, Dr. Takashi Shirozu of Kitakyushu Museum of Natural History, Professors Yoshihiro Hirashima, Katsura Morimoto and Toyohei Saigusa of Kyushu University for their constant encouragement. I am sincerely grateful to Professor Toyohei Saigusa of Kyushu University, for Copulation mechanism in Hepialid moths 39 his kindness reading and criticizing this manuscript. My thanks are also due to Dr. K. Mikkola, University of Helsinki, Finland, Dr. J. B. Birket-Smith, Insti tute of Comparative Anatomy, Copenhagen, Dr. G. S. Robinson and Miss P. Gilbert, British Museum of Natural History, Dr. N. P. Kristensen and Dr. E. S. Nielsen, Zoological Museum, University of Copenhagen, Dr. J. Dugdale of DSIR, New Zealand, Dr. N. Tindale of California, Dr. E. M. Antonova, Zoo logical Museum, University of Moscow, Dr. H. Inoue of Otsuma Woman's University, Mr. O. Yata of Kyushu University, Mr. N. Gyotoku of Fukuoka, Mr. T. Kawamura of Kitakyushu, Messrs. K. Ohara, T. Goto and N. Koda of Kyushu Univeristy, for their kindness giving me valuable informations and opportunities to examine the specimens.

References

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