148 DESCRIPTIONS OF PREPARATIONS. 



There is a pair of large toothed mandibles, but the structures corresponding 

 to the maxillae and labium of the Cockroach are here fused into a plate 

 which closes the mouth behind. The plate consists of a median and two 

 lateral lobes. Each lateral lobe represents a maxilla and carries a jointed 

 appendage, probably the maxillary palp. The median lobe, representing 

 the labium, carries a pair of jointed appendages, the homologues apparently 

 of labial palpi, and a central tubular projection, the spinneret, upon which 

 opens the common duct of the two silk glands. 



The three first somites carry each a pair of five-jointed limbs. They 

 represent the thoracic region of the imago, while the remaining ten somites 

 represent its abdomen. Of these ten, the two first somites have no 

 appendages but like the first body-somite (pro-thorax), and unlike the 

 second and third (meso- and meta-thorax), are pierced on each side by a 

 respiratory foramen, the spiracle or stigma. The succeeding four somites 

 also possess spiracles and carry unjointed, sucker-shaped limbs, armed ter- 

 minally and on the inner side with spines, and known as ' pedes spurii,' or 

 ' prolegs.' The two following somites have spiracles but no prolegs, and 

 the last of the two (the eighth abdominal) carries a dorsal horn characteristic 

 of the family Sphingidae, with the exception of a few species. The body is 

 terminated by two somites, of which the first, representing the large ninth 

 abdominal somite of the imago, is a narrow ring difficult to make out ; while 

 the last, the thirteenth larval somite reckoning from the head, is perforated 

 by the anus and carries a pair of anal prolegs. The anus itself is covered 

 by a triangular anal valve. 



The action of the spirit has destroyed the natural colour of the cater- 

 pillar. In life it is of a bright green colour, with yellow spiracles, the dorsal 

 horn black above and at the tip, yellow below, and the abdominal region 

 ornamented by seven oblique stripes, lilac above and white below. It feeds 

 upon the privet, ash, &c., and exists in the larval condition from the end of 

 July to the middle or end of September. During this period, it changes its 

 skin six times, increasing much in size after each moult, notably the last. 

 When full grown it has a brief period of quiescence, and then becomes very 

 restless. Its colour, especially on the dorsal surface, tends to a brownish 

 pink, and the pulsations of the heart become very visible and rapid. At 

 last it buries itself in the earth, penetrating to a depth of six to eight inches. 

 Here it hollows out a smooth-walled and waterproof chamber by moistening 

 the soil with the secretion of its silk-glands, and pressing it with its body. 

 It lines the chamber with silk and in about three days' time throws off the 

 caterpillar skin and appears as a pupa or chrysalis. 



The labrum is represented by two tubercles connected by a soft skin lying in 

 < front of the mandibles. In Pieris it is a corneous plate hinged upon the frontal 



