INSECT-LARV^ AND PUP^ 233 



The caterpillars of different orders may be distinguished 

 as follows : — Lepidopterous caterpillars have never more than 

 five pairs of abdominal pseudopods, carried on the third, fourth, 

 fifth, sixth, and last segments, and these nearly always bear 

 hooks. The caterpillars of Panorpae have bookless pseudo- 

 pods on all the abdominal segments. Saw-fly caterpillars 

 have bookless pseudopods on various abdominal segments, 

 but never on precisely those which bear pseudopods in a 

 Lepidopterous caterpillar. The second abdominal segment 

 always bears pseudopods in a saw-fly larva, never in a Lepi- 

 dopterous one. 



The following are exceptional Lepidopterous caterpillars : — 

 Geometers and some Noctuids walk by looping, and may 

 grasp their support by the hinder legs only. They have 

 fewer than the ordinary number of pseudopods. Some cater- 

 pillars have a forked tail, and then the last segment bears 

 no pseudopods. Some have a dorsal horn on the last segment 

 (Sphinges or hawk-moths). Caterpillars which burrow in 

 wood or earth have usually horny plates on the dorsal surface 

 of the segments, sometimes on the prothorax only. Footless 

 caterpillars occur in a few Lepidopterous families. 



3. The Maggot. — The head is reduced to a vestige, which 

 can be completely withdrawn into the thorax, and bears 

 neither eyes nor antenna, nor true jaws. There are no legs 

 or pseudopods. There is a pair of large spiracles (often 

 the only ones) on the truncated hinder end of the body. 

 This larva is found only among the higher Diptera. 



There are three well-marked kinds of pupa : — 



1. The free-limbed ("incomplete") pupa. — Here the fly, 

 more or less complete in internal structure, and usually com- 

 plete externally, is enclosed in a temporary pupal skin, which 

 accurately fits every part of its body. Each limb has its own 

 sheath, and may be freely mobile (Trichoptera). Examples 

 of the free-limbed pupa occur in Coleoptera, Hymenoptera, 

 Neuroptera, Nemoceran Diptera, and Trichoptera. 



2. The agglutinate ("obtected") pupa. — Here the fly, after 

 emerging from the larval skin, and enclosed only by the 

 temporary pupal skin, exudes a fluid, which sets on exposure 

 and glues down all the appendages, rendering the surface 

 dense and shiny. Nearly all Lepidoptera and some Coleoptera 

 (Staphylinidse and Coccinellidae) have pups of this kind. 



