Imago of Death's-head Moth. 79 



Sphingidae have no ocelli, and the genus Aeheroutia has the spiral 

 proboscis much shorter than other genera belonging to the family. 



In their possession, when larvae, of provisional organs, of which 

 no traces are left in the perfect insect, the Lepidoptera resemble the 

 Neuroptera and Hymenoptera Phytophaga, amongst the orders dis- 

 tinguished by quiescence in the pupa-stage, and said consequently 

 to have a ' perfect metamorphosis,^ as also the Orthoptera Am- 

 phibiotica amongst Ametobolous insects. The true Hymenoptera, 

 on the other hand, and the Coleoptera, with a few exceptions, 

 possess no provisional organs in this larval state, though they pass 

 into perfect quiescence as pupae. This latter condition therefore 

 should be taken as the essential characteristic of a ' perfect meta- 

 morphosis/ 



For the characteristics of perfect and imperfect metamorphosis, see 

 Gerstaecker^ Klassen und Ordnungen des Thierreichs, bd. v., 

 p. 189. 



28. Larva of Goat Moth {Cossus Lignipei-da), 



Dissected so as to show the various internal organs of vegetable life, and the points 

 in which they differ from those observable in the perfect insect. 



The dorsal integuments have been divided down the middle line, 

 and turned outwards on either side, together with the muscles 

 which were in connection with them. The greater part of the body- 

 cavity is occupied by lobulated masses of adipose tissue, known 

 as the ' fat body,^ or ^ rete,' which disappear almost completely 

 in the adult insect of the orders with a perfect metamorphosis. 

 In the middle line we see the digestive tract, which passes, without 

 forming any convolutions at right angles to the long axis of the 

 body, from the mouth to the anus. Its most anterior segment, 

 seen in this Preparation, is the transparent- walled oesophagus upon 

 which is seen the highly developed nervus recurrens. This nerve is 

 connected, anteriorly, with a series of three ganglia which are placed 

 one behind the other, and correspond with the single ganglion 

 frontale of some insects; and, posteriorly, at the junction of the 

 oesophagus and stomach, with a plexus into which the two lateral 

 stomato-gastric nerves enter. The stomato-gastric nerves undergo 

 less change in metamorphosis than perhaps any other system of 



