150 DESCRIPTIONS OF PREPARATIONS. 



stigmata. In the thoracic region the nerve breaks up into three primary branches. 

 The median divides right and left as in the abdominal region, and supplies the lon- 

 gitudinal trunk which unites the prothoracic to the first abdominal stigma, as well 

 as the tracheae it gives off. Each side branch runs backwards and unites with the 

 ganglion, first of all giving off a lateral branch, the nervus lateralis transversus of 

 Cattie, which joins the first nerve given off by the ganglion. The stomatogastric 

 system consists, according to Newport, of a ganglion frontale and nervus recurrens : 

 and of two ganglia in connection (like the paired system of the Cockroach) with the 

 posterior aspect of the supra-oesophageal ganglion. The latter supply nerves to the 

 tracheae of the head. The ocelli, as usual, have each a single lens. Beneath the 

 lens lies a number of black pigment cells imbedding a crystalline body composed 

 of several parts (Carriere). 



The stigmata possess a complete apparatus by which they may be closed. The 

 tracheal stems arising from them are all connected on each side by a longitudinal 

 trunk which in the meso- and meta-thoracic somites gives off an external branch 

 furnished with the usual dosing apparatus of a stigma. No external indications of 

 stigmata, however, are visible in these somites in Sphinx, but Prof. Westwood 

 possesses a dried specimen of Cossus in which they are clearly visible. W. Miiller- 

 Blumenau has found an aquatic Lepidopterous larva (Catadysta pyropalis) living 

 in Brazil, in which all the stigmata are closed and respiration is carried on by 

 filamentous branchiae, but there are two closed thoracic stigmata, which he places 

 between the pro- and meso-thorax and between the meso- and meta-thorax. He 

 states that he has also found them in many terrestrial larvae. The wings arise 

 in close connection with the meso- and meta-thoracic branches. There are 

 three pairs of cephalic stigmata in the embryo (Hatschek). 



The digestive tract consists of an oesophagus, and an intestine and rectum 

 lined by a cuticle, and a chylific stomach or mesenteron. There are six Malpighian 

 tubes with a beaded exterior which open as usual into the beginning of the intestine. 

 Two short salivary glands open into the mouth, and a pair of serictaria or silk 

 glands by a common duct on the spinneret *. The rudimentary genital organs lie 

 one on either side the heart under the fifth abdominal tergum. A delicate filament 

 may be traced from each organ round the intestine. Herold figures these filaments 

 as extending in Pieris Brassicae, in the male to the anterior border of the ninth 

 somite ; in the female to the anterior border of the eighth somite, and into con- 

 nection with two oval bodies at its posterior border. An abundant fat body fills 

 the body-cavity, or coelome. The blood is acid as in all caterpillars with one ex- 

 ception hitherto examined, and contains amoeboid blood-corpuscles. It is green, 

 and the colour is due to metachlorophyl (Poulton). 



There are two types of larval (or young) Insecta : one known as Campodei- 

 form, from a more or less close resemblance to the genus Campodea among Thy- 

 sanura ; the other as cruciform, of which a caterpillar may be taken as a good 

 example. The Campodeiform larva has the typical regions of the body clearly de- 

 fined, mouth parts adapted for biting, well developed ambulatory thoracic limbs, 

 and frequently terminal abdominal jointed appendages. The outlines of the body 



1 Poletajew (Z. A. viii. 1885) states that the silken thread is single in the Tenthredinidae, 

 but double and twisted in Lepidoptera. Hence he disputes the statement that the ducts of the 

 serictaria have a common outlet. 



