160 DESCRIPTIONS OF PREPARATIONS. 



Changes have taken place in the internal organs. The supra- and sub-oeso- 

 phageal ganglia have coalesced round the oesophagus. The mesothoracic ganglion 

 appears to abort \ the prothoracic persists and is approximated to the metathoracic 

 which has coalesced with the first abdominal. The second and third abdominal 

 ganglia abort, but the nerves which they give off persist. The abdominal ganglia 

 of the imago correspond to the four last ganglia of the caterpillar. A remarkable 

 structure, the chorda supraspinalis, overlies the abdominal ganglia, extending from 

 the spot where the nerves arise from the sixth, an aborted ganglion, to the last 

 ganglion. It is well-developed in the imago, and has been found by Burger in a 

 large number of Lepidoptera. It is triangular in section and is intimately united by 

 one angle to the neurilemma of the nerve cord whilst lateral muscles are attached to 

 its two other angles extending thence to the abdominal walls. It is composed either 

 of reticular cell-tissue with intervening jelly, or of vesicular cells. The chorda forms 

 a strong attachment for the muscles, and the latter roof in the ventral blood-sinus 

 (see under Cockroach, p. 144). There are vesicles developed on the tracheal 

 branches in the abdomen. In the digestive tract there is a pharyngeal sac which 

 can be dilated and contracted by systems of muscles. The oesophagus is long, and 

 has at its stomachal end a non-pedunculated sucking stomach. The chylific 

 stomach of the caterpillar is much reduced. The Malpighian vessels have lost 

 their bead-like caeca. The intestine is long and the colon, as in many Lepidoptera, 

 has a large dorsal caecum. 



The testis is single externally, the two embryonic testes having become en- 

 veloped in a common sheath, as is often the case in Lepidoptera 2 . But there are 

 two vasa deferentia : they are long much contorted tubes, and each duct receives 

 an accessory tubular gland. 



Each ovary consists of four long convoluted ovarian tubules united terminally 

 by a ligament, both inter se and to the dorsal wall of the abdomen. The bursa 

 copulatrix is large and pyriform, and a slender canal starts from its neck on the 

 ventral anterior surface, curves round the neck and enters the side of the vagina. 

 At its entrance a slender caecum is attached to the vagina which probably 

 represents a spermatheca. There are two accessory tubular glands which dilate 

 each into a pyriform enlargement, then fuse, and their common duct opens dorsally 

 into the vagina near its exit. This exit is immediately below the anus 3 . 

 enlarged galea ; a labium with mentum, three-jointed palps, paraglossae and ligula. In other species 

 of the same genus the mandible is a simple lobe, the laciniae of the two maxillae are lost, and 

 the galeae are transformed into more or less typical antliae capable of being coiled up and closely 

 united, and there are no paraglossae. Mandibles as more or less simple lobes articulated to the 

 head appear to exist in most Micro-lepidoptera. 



1 So thinks (Newport Phil. Trans. 1834, P- 394), but with reference to Vanessa Urticae he 

 says (p. 416) that the prothoracic and mesothoracic, his second and third, ganglia fuse. Herold 

 states the same fact with reference to Pieris Brassicae. 



2 Cholodkowsky has shown that when the external capsule is removed, the apparently single testis 

 consists of eight testicular follicles, four to each vas deferens. The follicles are arranged in various 

 ways within the sheath. Hepialus Humuli retains the testis in the primitive condition, i. e. four free fol- 

 licles on each side. In Pygaera anachoreta, &c., each set of follicles is contained within a separate 

 capsule : but in most Lepidoptera the follicles of both sides are contained in a common capsule. 



3 There can be little doubt that the canal connecting the bursa copulatrix to the vagina, 

 itself represents the primitive vagina. The aperture of the bursa is in the typical position of the 

 vaginal aperture. The canal in question has to pass round the neck of the bursa to gain its 

 destination. The bursa in all other insects is a dorsally-placed appendage to the vagina. These 



