Observations on the Genital System and Alimentary Canal of a Lamiid Beetle, Nupserha bicolor By N. DUTT

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1 393 Observations on the Genital System and Alimentary Canal of a Lamiid Beetle, Nupserha bicolor By N. DUTT (From the Jute Agricultural Research Institute, Barrackpore, West Bengal) With one plate (fig. 3) SUMMARY The genital system and alimentary canal of both sexes of adult Nupserha bicolor s.sp. postbrunnea have been examined. In the female, the posterior end of the rectum is enclosed within a membranous jacket. The membranous jacket represents the tenth segment and is much more prominent than in the male. The jacket enclosing the rectal end runs a short course parallel with the vaginal passage through a common chitinous capsule representing the ninth segment, in which the openings of the anus and the genital passage lie. The chitinous capsule thus looks like a 'cloacal chamber'. It disappears when the ovipositor is shot out. In the male, the posterior end of the rectum runs straight to the anus. The anus is located within the membranous remnant of the tenth segment. In the genitalia of the female, one remarkable peculiarity is observed distally in the eighth tergite of the adult female. At this level, the eighth tergite and the dorsal portion of the intersegmental membrane between the eighth and ninth segments lie superimposed upon one another and unite medially. On one side a condyle and an oblique socket are formed. The condyle of each side projects into the socket of the other side to form a ball-and-socket apparatus. The mechanism disappears proximally in the eighth tergite. The structure is absent in the male. INTRODUCTION 1KTUPSERHA BICOLOR Thorns., subspecies postbrunnea Dutt, was J. V recently reported (Dutt, 1952) on Corchorus olitorius L. (jute). Within a few years it has turned out to be a major pest of the crop. The egg-laying female is the destructive phase. Its genitalia and alimentary canal are closely associated and genital system is characterized by peculiarities not recorded before. Not much information is available on the genital system of lamiid beetles. In this paper an account of the structural peculiarities of the genital system of N. b. postbrunnea is presented. MATERIAL AND METHODS Adult beetles of both the sexes were fixed in Carnoy-Lebrun fixative for about 10 min, dechitinized in Mukerji's mixture (1937), dehydrated, cleared in cedarwood oil, and embedded in paraffin wax. Sections were cut at 10 (i and stained in Mallory's triple stain. A 1% aqueous solution of phosphomolybdic acid was used. The genital system and alimentary canal of the adult beetles were also dissected out under the stereomicroscope from fresh specimens and stained in borax-carmine. Specimens were treated with 10% hot KOH for about 10 min for the study of the genitalia. [Quarterly Journal of Microscopical Science, Vol. 99, part 3, pp , Sept ]

2 394 Butt The Genital System of a Lamiid Beetle FEMALE GENITAL SYSTEM The ovarioles are five on each side. The ovarioles of each side open into a short oviduct, which bends to unite with the common oviduct. The common oviduct is short. It opens into the bursa copulatrix. The bursa copulatrix is an elongated tube bent in the form of a U. The bursa copulatrix is flexed on the ovary spermabheca bursa copu/cttrix membranous jacka (seg.x). ovipositor spiculum gastrale capsule (seg. IX) 'cloaca 1 - FIG. I. The genital system of the female (diagrammatic). ventral side, resting over the styliform rod. The terminal portion of the bursa copulatrix leads into a narrow passage, the vagina. The vagina bends down to pass into the chitinous capsular sheath. The ventral wall of the capsular sheath reaches anteriorly the end of the vagina, thus separating the vaginal portion from the body of the bursa copulatrix. The capsule runs as a wide cylinder as far as the posterior end of the fifth sternite. The rectum, enclosed within the membranous j acket, passes through this capsular sheath, running parallel with the vaginal passage. The common chitinous capsule represents the ninth abdominal segment, in which the openings of the rectum and genital passage lie (fig. i). The chitinous capsule thus represents a kind of cloaca. The cloaca

3 Butt The Genital System of a Lamiid Beetle 395 disappears as the genital passage evaginates at the time of egg-laying. Bugnion (1933) also reported a 'manchon cloacal' in the lamiid beetle Callidium sanguineum. The vagina lies ventrally to the rectum. The rectum reaches nearly the posterior extremity of the capsule, while the vaginal passage during rest remains at the anterior end of the capsule. The rectal jacket enclosing the spiculum gastra/ecoxite seg./x- 017 mm sternite Vll/ FIG. 2. The genital segments of the female (diagrammatic). rectum is closely pressed against the wall of the vaginal passage. The appendages of the ninth segment or the chitinous capsule (coxites and styli) are borne on the vaginal end and generally occupy the middle and a little of the posterior half of the capsule at the time of rest (fig. 2). Bugnion (1933) holds the view that these appendages (ovipositor) have been derived from the tenth abdominal segment of the larva, while Tanner (1927) pointed out that only the appendages of the ninth segment persist. Styli bear sensory hairs, as in C. sanguineum; Bugnion (1933) named these 'antennes posterieures'. The vaginal passage, including the length of the appendages of the ninth segment, is slightly more than half the length of the rectum, which runs through the capsular sheath. The capsule narrows down at the posterior extremity to open to the exterior through the eighth segment. The eighth segment is fringed at

4 396 Dutt The Genital System of a Lamiid Beetle the posterior end with stout hairs. The eighth sternite is continued anteriorly like a pyramid. From the anterior end of the pyramid runs a very stout cylindrical rod with a small cavity in the interior. This styliform rod corresponding to the spiculum gastrale (Mukerji and Bhuya, 1937) or tigelle valvaire (Bugnion, 1933); it reaches as far as the third abdominal sternite. Its terminal end remains free within the abdominal cavity. Longitudinal muscle-fibres run along the length of the rod from the apex to the base parallel with it. In addition there are longitudinal muscles which arise from the apex of the rod and run in an oblique direction to become attached to the common oviducal wall. A pair of muscle bands runs from the ventro-lateral region of the U-shaped bursa copulatrix to the eighth sternite. At the time of depositing the egg, the capsule becomes evaginated and passes beyond the posterior extremity of the abdomen. At its terminal opening, the appendages of the ninth segment project to the exterior. When the capsule becomes everted, its internal surface becomes external as the evaginated portion slides down, leaving the rectum behind; but it carries along the vaginal portion, which straightens out to form a duct leading into the opening of the everted posterior end of the everted capsule. On account of the traction, the bursa copulatrix and the vaginal passage form more or less a straight line. Eversion of the capsule occurs when the abdomen contracts. Retraction occurs by the contraction of the muscle-fibres that run from the apex of the rod to the anterior wall of the common oviduct and from the bursa copulatrix to the eighth sternite. The capsule is composed of a thick chitinous wall which has a series of transverse lines dividing the chitin into narrow strips. Transverse lines are found on the internal surface of the chitin of the capsular wall; these are on the external surface when the capsule evaginates with eversion of its fold. The lines on the capsule allow it to be crumpled in the course of eversion through the narrow passage bounded by the eighth segment. Its dorsal and ventral walls are fused laterally and admit apically the rectal jacket, enclosing the rectum and the vagina (fig. 3, A). Posteriorly, the capsule is dorsoventrally flattened and slightly depressed medially from above and below. Its lateral cavities look like horns. The dorsal wall of the capsule is dorsal to the rectum and lies a little ahead of the ventral capsular wall. The appendages of the eighth segment have disappeared. One remarkable peculiarity is noted distally in the eighth tergite: there is a very faint mid-dorsal line dividing the tergite into right and left halves. On examination of a cross-section this line is found to be formed by the apposition of the eighth tergite and the intersegmental membrane between the eighth and the ninth segments. They lie closely superimposed upon one another and unite medially along the sutural line. On each side a condyle and an oblique socket are formed. The condyle of each side projects into the socket of the other side. The condyles fit into the sockets (fig. 3, B). This ball-and-socket FIG. 3 (plate). A-D and F are transverse sections at various levels of the body. B is at the level of the anterior end of the eighth tergite of a female; c and D are more posterior sections. E is a longitudinal section.

5 seg. IX caeca cardiac valve FIG. 3 N. DUTT

6 Dutt The Genital System of a Lamiid Beetle 397 apparatus gradually disappears towards the posterior end of the eighth tergite (fig. 3, c, D). At this stage, the zigzag courses of the tergite and the intersegmental membrane are clearly visible. The structure is absent in the male. Sharp and Muir (1912) have made an important study of the male genitalia of Coleoptera in general, while Tanner (1927) has made a similar important study of the female genitalia; but none of these authors has reported a mechanism such as is found in this beetle. Subsequent studies by Metcalfe (1932), Snodgrass (1935), Bissel (1937), Tanner (1943), and Bruhn (1947) have not recorded such a structure in Coleoptera. Bugnion (1933), who has made important contributions to the anatomy of C. sanguineum Linn, (a lamiid beetle), has not recorded such a joint. The ball-and-socket mechanism allows widening of the passage through which the capsule protrudes to the exterior at the time of evagination; it holds the capsule tight afterwards. The eversion of the capsule puts the ovipositor far beyond the tip of the abdomen for insertion of the egg into the host plant; the latter was slit by the mandibles. Dutt (19566) has reported the formation of a pit by the action of the mandibles. These serve in the female as an essential accessory genital organ during the pre-ovipositional stage. The spermatheca, which has the shape of a baby's feeding-bottle, is a conspicuous structure. Its connexion with the spermathecal gland is marked by a pin-shaped chitinous valve. The spermathecal gland opens into the anterior end of the common oviduct through the spermathecal duct. Branches of the gland unite to form a common duct which is continuous with the spermathecal duct. The 'vesicule oblongue (gland colloide)', which opens independently in C. sanguineum (Bugnion, 1933), is absent in N. bicolor. Repeated matings have been observed under laboratory conditions, though the female has a well-developed spermatheca. THE MALE GENITAL SYSTEM The two follicles of the testis of each side are placed laterally at the anterior region of the abdomen. The first follicle lies at the level of the second abdominal sternite and the second at the level of the third. They are more or less spherical in outline, but somewhat flattened laterally. The duct, on leaving each testis, receives a duct that has been formed by the union of several ductules arising from the accessory glands. The accessory glands are elongated tubes occurring in large numbers. The duct of the testis, after receiving the duct of the accessory gland, continues backwards and the two unite to form the sperm duct or vas deferens. The vas deferens swells up to form an elongated tube, the seminal vesicle. The seminal vesicle is fusiform and is usually placed on the right side of the abdomen at the level of the third and fourth sternites. It receives a large number of fine tracheal capillaries, obviously ensuring better oxygenation of the spermatozoa stored there. The seminal vesicle continues as a narrow ejaculatory duct. The ejaculatory duct pursues a zigzag course while passing through a highly muscular bulb; it is connected with the apex of the membranous internal sac or flagellum (fig. 4). The flagellum, which is introverted, extends back as far as the junction of the bulb D d

7 398 Dutt The Genital System of a Lamiid Beetle and the internal sac. When the flagellum is everted, it drags out the ejaculatory duct. The flagellum is chitinized and very spiny at the anterior region when folded in. The spines are directed backwards. The horse-shoe shaped structure disappears when the flagellum is shot out by the action of three sets of muscle fibres. One set connects the middle portion of the internal sac, at the level of the anterior region of the flagellum, with the struts of the median lobe. The testis accessory gland muscle fibre 0-30 mm median orifice 'legmen FIG. 4. The genital system of the male (diagrammatic). other set runs ventral to the median lobe and connects it with the membranous internal sac. The third set connects the internal sac with struts of the tegmen. The internal sac is evaginated through the median orifice during mating; this has been stated by Sharp and Muir (1912) to be the general rule. The bulb is highly muscular and is connected with the internal sac that encloses the flagellum. Thes.e together bend in the form of a horse-shoe. The sac enclosing the flagellum is placed at the level of the fourth and fifth sternites. It communicates with the chitinized arched tube, or with the median lobe by a median orifice anteriorly; two struts arise from its dorsolateral edge in the posterior region. The tegmen, placed anteriorly to the median lobe, is a ringlike structure with a ventral strut and a pronounced cap-piece on its dorsal surface. The cap-piece has two lobes united at the base. These lobes bear stout hairs posteriorly.

8 Dutt The Genital System of a Lamiid Beetle 399 ALIMENTARY CANAL The buccal cavity leads to a short oesophagus which, at the level of the suboesophageal ganglion, leads into the crop. The crop, which runs a straight course, is a voluminous sac, extending as far as the level of the second thoracic ganglion. Behind the crop is situated the simple proventriculus, which is invaginated into the anterior end of the mesenteron to form the cardiac valve (fig. 3, E). At the anterior end, the mesenteron gives out caeca (fig. 3, F). The latter are absent in the lamiid beetle C. sanguineum (Bugnion, 1933). These caeca are short; they are directed forwards and are applied against the digestive tube. The anterior end of the mesenteron is marked by small, wavy bulgings of its wall. The posterior end of the mesenteron bends to form a loop and then opens into the intestine. The junction between the two is marked by six long Malpighian tubules. In the mesenteron, the circular muscles are very thin and the epithelial cells are very small. The intestine is a narrow tube. It dilates in the middle and then narrows to form the rectum. The course of the rectum in the posterior end of the female is different from that of the male. In the male it runs a straight course, ending in the anus. The anus is located within the membranous remnant of the tenth segment. In the female the posterior end of the rectum is enclosed within a membranous jacket. The jacket enclosing the rectal end runs a short course, parallel with the vaginal passage, through the chitinous capsule or the ninth segment, as was mentioned before. Since the anal opening is located at the end of the membranous jacket, this seems to represent the tenth somite. This structure is much more prominent than it is in the male. The presence of such a structure has not been reported in the lamiid beetle C. sanguineum (Bugnion, 1933). Sincere thanks are due to Dr. B. C. Kundu, Director of the Jute Agricultural Research Institute, for his encouragement during the course of this work, and to Professor D. Mukerji, of University College of Science and Technology, Calcutta, for helpful criticism. The author is also under great obligation to Professor O. W. Richards of Imperial College of Science and Technology, London, for his valuable suggestions. REFERENCES BISSEL, T. L., Ann. ent. Soc. Amer., 30, 242. BRUHN, A. F., Gr. Bas. Nat., 8, 1. BUGNION, E., Proc. Verb. Soc. Bordeaux, 85, 106. DUTT, N., Nature, 170, a. Jute Bull., 18, Bull. ent. Res., 47, 777. METCALFE, M. E., Quart. J. micr. Sci., 75, 49. MUKERJI, D., Curr. Sci., 6, 16. and BHUYA, H. M. A., J. Morph., 61, 175. SHARP, D., and Mum, F., Trans, ent. Soc. London, 60, 477. SNODGRASS, R. E., Principles of insect viorphology. New York and London (McGraw- Hill). TANNER, V. M., Trans. Amer. ent. Soc, 53, Gr. Bas. Nat., 192, 1.

Internal Morphology. 1.Cut the legs and wings (if present) off your specimen. 5.Use forceps to pull skeleton apart, exposing internal systems.

Internal Morphology. 1.Cut the legs and wings (if present) off your specimen. 5.Use forceps to pull skeleton apart, exposing internal systems. Internal Morphology Insect Dissections Often the best approach to understanding internal morphology is by way of a dissection. For this reason, the entire chapter should be treated as a laboratory activity.