Studies on the Anatomy of the Sugarcane Moth Borers Vi
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STUDIES ON THE ANATOMY OF THE SUGARCANE MOTH BORERS VI. Comparative Study of the Female Genitalia BY V. D. PURl, M.Sc. (HONS.), F.R.E.S. (Sugarcane Research Institute, Pusa, Bihar) Received October 22, 1957 (Communicated by Shri K. L. Khanna, F.A.SC.) CONTENTS PAGE 1. INTRODUCTION ........ 4 9 6 I 79 2. MATERIAL AND METHODS ...... Q • I 0 81 3. DESCRIPTION OF THE VARIOUS PARTS- (a) Structure of the Abdomen .... 81 (b) Female Genitalia: (i) The Ostium Oviductus and the Ovipositor Q ~ O O 82 (ii) The Genital Chamber and the Ostium Bursae • g Q W 83 (iii) The Ductus Bursae and the Corpus Bursa~ g O O Q 84 (iv) The Ductus Seminalis .... D J * • 85 4. DIAGNOSTIC CHARACTERS ...... D O O O 85 5. SUMMARYAND CONCLUSIONS .... I 0 O Q 85 6. ACKNOWLEDGMENTS ...... D O • t 87 7. REFERENCES ........ I I O I 87 8. EXPLANATION OF PLATES ...... ~ O 9 ~ 88 1. INTRODUCTION THE study of the genital armature in insects is obviously the most important item in systematic work and has evoked considerable interest in modern taxonomy because of its definite and reliable bearings on the identification and classification of different groups of insects. Tams (1926) stated that the genital armature in many groups of insects both in the male and the female presents characters valuable in the identification of different species. 79 80 V.D. PtrRi The study of the female genitalia in Lepidoptera has been far more neglected in comparison to that of the male genitalia possibly because of the fact that the female armature was considered comparatively simple (McDonougli, 1911). Although the genital armature of different sugarcane moth borers (Lepidoptera) has been studied by quite a few workers in the past, the fact remains that very little attention has been paid to the female genitalia. Bisset (1939) proposed the name Chilo trypetes (Bissetia steniellus) for the new pyralid borer from Gurdaspur (Panjab) and compared the male and female genitalia of three different species of the genus Chilo, viz., Chilo sup- pressalis, C. zonellus and C. trypetes, with the help of their illustrations. He did not, however, describe the female genitalia of these species. Gupta (1940) studied the genitalia of four different species of sugarcane moth borers, viz., Chilotra~a infuscatellus, C. auricilia, Proceras indicus and Chilo zonellus, but did not describe these structures in detail. His descriptions were further not supported by illustrations. Trehan and Butani (1950) discussed the systematic position of Chilo zonellus and C. simplex by illus- trating the difference between the male genitalia of these species. They did not compare the female genitalia thus leaving a considerable gap in know- ledge. Kapur (1950) considered mainly the male genitalia and other charac- ters in connection with his proposed revision of the taxonomy of crambinid moth borers of sugarcane. He did not describe the detailed structure of the ovipositor in case of Chilotrcea infuscatellus, C. auricilia and Chilo tumidi- costalis. The female genital openings also received inadequate attention. Besides his study was confined to a single subfamily, Crambin~e. In the present paper, three subfamilies of the family Pyralidce and another sub- family Agrotidce of the family Noctuidce, have been presented, thus including another three important species of sugarcane moth borers, viz., Scirpophaga nivella (Schoenobiince-Pyralidve), Emmalocera depressella (Anerastince-Pyra- lidce) and Sesamia inferens (Agroti&e-Noctuidce). Narayanan and Venkat- raman (1951) confirmed the identity and synonymy of Scirpophaga nivella and S. monostigma by comparing their male genitalia but they too did not attach any importance to the female genitalia which according to Kaput (loc. cit.) are more helpful in separating out the different species of the same genus. Krishnamurti and Usman (1952) have added much to knowledge of the morphology of Sesamia inferens but they also have ignored illustrations of female genitalia of the species. Puri (1957a) described and illustrated the male and female genitalia of the sugarcane stem borer Chilo tumidicostalis. He (1957b) also described the morphology of the female genital chamber in Emmalocera depressella, root borer moth of sugarcane. Studies on the Anatomy of the Sugarcane Moth Borers--Vl 81 The present work was undertaken with a view to bridging the existing gaps in knowledge with respect to the detailed anatomy of female genitalia in eight species of sugarcane moth borers. 2. MATERIAL AND METHODS The moths of seven different species, viz., Scirpophaga nivella, Chile tumidicostalis, C. zonellus, Chilotrma infuscatellus, C. auricilia, Emmalocera depressella and Sesamia inferens were reared in the laboratory at Pusa, Bihar from field collections of larva~ and pup~. Those of Bissetia steniellus were imported from Uttar Pradesh and Panjab for the present work. Permanent slides of the entire insects as well as those of the abdomen alone were prepared by treating the specimens with 10 to 15~o KOH solution, washing them under a current of water for about 8 hours, dehydrating, clear- ing in carbo-turpentine, turpentine, cedar wood oil and finally mounting them in turpentine canada balsam. The specimens were also stained with eosin in 90~ alcohol before clearing them in carbo-turpentine or pure turpentine as described by Puri (1954). This method proved quite satisfactory. The micro-photographs reproduced in the present paper were taken directly from slides of the various structures duly stained. 3. DESCRIPTION OF THE VARIOUS PARTS (a) Structure of the Abdomen The abdomen in females is generally elongate, with a comparatively thick and less tapering abdomen than that of males. It is composed of ten segments. The last three segments, viz., 8th, 9th and 10th are usually modified to form the genitalia in these female moths but it has been observed that the 7th segment may also take part in such formations in particular cases like that of Emmalocera depressella where the folds of the genital opening or th0 ostium bursae do extend upto the 7th abdominal segment. The last two or three segments are usually retractible within the last visible segment. There are only seven apparent segments in the female abdomen of these insects. The sclerotized portions of the unmodified abdominal segments consist of a t¢rgite and a sternite. These are separated by a membranous pleural region bearing the seven abdominal spiracles. The segments are connected by conjunctival membranes and each tergite and sternite normally overlaps the following tergite and sternite. A narrow acrotergite is present in the tergites of all the unmodified segments except the first. The internal antecosta formed by the antecostal suture bears the principal muscles. The 8th abdominal spiracle present in the larval stage is obliterated but its remanents may be observed in the freshly hatched moths. The entire surface of the abdomen is covered with thick scales and hairs. B2 82 V.D. PURI The general description of the tergites and the sternites of the abdomen is somewhat similar to that given by Madden (1944). The tympana are a pair of vesicles which are sac-like or bladder-like structures closely associated with the first pair of abdominal spiracles on each side, extending upto the 4th abdominal segment in some cases. These are well developed and quite prominent structures, believed to be auditory in function (Imms, 1951), and are innervated from the last thoracic ganglion. (b) Female, G¢nitalia The study of the genitalia in these insects is possible only in denuded specimens made transparent for this purpose, because these are always con- cealed by a thick clothing of hairs and scales. The female genitalia in these insects are usually of ditrysian type quite common in most of the Lepidoptera, as described by Tuxen (1956). In this type of genitalia the two reproductive openings, viz., the ostium oviductus and the ostium bursae are widely separated. O) Ostium oviductus and the ovipositor.--The ostium oviductus opens in the last or the 10th segment cephalad and ventrad of the anus. Both ostium oviductus and anus are between the two lobes of the false ovipositor or the papill~e anales. The ovipositor lobes are usually elongated so as to serve as an extensible ovipositor. These papillae anales are heavily sclerotized in all these moths, being in the form of an elongated plate. The papillae anales are united or fused so as to appear an elongated plate-like ovipositor in almost all the Pyralids but in case of Sesamia inferens (Noctuidce), the two lobes are partially fused and appear to be separated out as shown (Plate XVIII, Fig. 8). The papillae anales of the false ovipositor are modified differently in different species of these sugarcane moth borers which are typical of the different species. It is somewhat betel-shaped in Scirpophaga nivella (Plate XVIII, Fig. 1). It appears to be somewhat like a slipper sole or param~ecium in case of Chilo tumidicostalis (Plate XVIII, Fig. 2). It is somewhat flat in the middle and tapering towards both the ends just like a fiver fluke in Chilo zonellus (Plate XVIII, Fig. 3). It is interesting to note that the two lobes or the papillae anales do not appear to be separated apart in Chilo species. In Chilotrcea #fuscatellus (Plate XVIII, Fig. 4) there is a notch or a small bowl- shaped concavity at the anterior end of the fused false ovipositor which is situated in the middle of the anterior ends of the two lobes. The entire ovipositor appears to be like a slipper with a flat toe. It is comparatively flat and greatly sclerotized plate-like structure in Chilomea auricilia (Plate XVIII, Fig. 5). The two lobes or the papillae anales are almost completely fused to form a single elongated plate-like ovipositor in Bissetia steniellus (Plate XVIII, Fig. 6) which in the lateral view gives a side view of the funnel.