TRACHEATA. 42 1 



Tipulidae the larval skin is thrown off at the pupa stage, and in some cases 

 the pupae continue to move about. 



The larvae of the Neuroptera are hexapodous voracious forms. When the 

 larva becomes a pupa all the external organs of the imago are already 

 established. The pupa is often invested in a cocoon. It is usually quiescent, 

 though sometimes it begins to move about shortly before the imago emerges. 



In the Coleoptera there is considerable variety in the larval forms. As a 

 rule the larvae are hexapodous and resemble wingless Insects. But some 

 herbivorous larvae (e.g. the larva of Melolontha) closely resemble true 

 caterpillars, and there are also grub-like larvae without feet (Curculio) which 

 resemble the larvae of Hymenoptera. The pupa is quiescent, but has all 

 the parts of the future beetle plainly visible. The most interesting larvae 

 among the Coleoptera are those of Sitaris, one of the Meloidae (Fabre, No. 

 409). They leave the egg as active hexapodous larvae which attach them- 

 selves to the bodies of Hymenoptera, and are thence transported to a cell 

 filled with honey. Here they eat the ovum of the Hymenopterous form. 

 They then undergo an ecdysis, in which they functionally lose their append- 

 ages, retaining however small rudiments of them, and become grubs. They 

 feed on the honey and after a further ecdysis become pupae. 



In the Lepidoptera the larva has the well-known form of a caterpillar. 

 The caterpillars have strong jaws, adapted for biting vegetable tissues, 

 which are quite unlike the oral appendages of the adult. They have three 

 pairs of jointed thoracic legs, and a variable number (usually five) of pairs 

 of rudimentary abdominal legs the so-called pro-legs. The larva undergoes 

 numerous ecdyses, and the external parts of the adult such as the wings, etc., 

 are formed underneath the chitinous exoskeleton before the pupa stage. 

 The pupa is known as a chrysalis and in some Lepidoptera is enveloped in 

 a cocoon. 



The Hymenoptera present considerable variations in the character of the 

 larvae. In the Aculeata, many Entomophaga, the Cynipidae, etc., the larvae 

 are apodous grubs, incapable of going in search of their food ; but in the 

 Siricidae they are hexapodous forms like caterpillars, which are sometimes 

 even provided with pro-legs. In some of the Entomophaga the larvae have 

 very remarkable characters which have already been described in a special 

 section, vide pp. 418, 419. 



Before proceeding to the consideration of the value of the 

 various larval forms thus shortly enumerated, it is necessary to 

 say a few words as to the internal changes which take place 

 during the occurrence of the above metamorphosis. In the 

 simplest cases, such as those of the Orthoptera and Hemiptera, 

 where the metamorphosis is confined to the gradual formation 

 of the wings, etc. in a series of moults, the wings first appear as 

 two folds of the epidermis beneath the cuticle on the two 

 posterior thoracic segments. At the next moult these processes 



