METAMORPHOSIS. 



31 



wait for their prey (CioiNUELiDJi;) are not adapted for rapid 

 motion. Those that live surrounded with their nutriment (Scara- 

 bjeibje, many Rhynchophora, etc.) are usually sluggish. As 

 a rule the six legs are fully developed, although occasionally one 

 pair may be rudimeutary and adapted for a special purpose (as in 

 the Passalid^e). Sometimes they are very small, and in the Cur- 

 culioistd^ they disappear altogether. This is not the case with 

 -all the E.HYNCHOPHORA, as appears to be sometimes thought, for 

 in the Anthribid,e the larvae of some of the genera are legless, 

 whereas in others legs are present (e. g. Cratoparis and Arceocerus); 

 while in the larva of the curious European species Choragus shep- 

 pardi the legs are replaced by three pairs of thoracic sac-like 

 pseudopods (Sharp, I.e. p. 290). Probably in most of the apodous 

 species the rudiments of legs might be found underneath, if not 

 outside, the integument, if the insects were dissected and micro- 

 scopically examined. 



There are two forms of Coleopterous larva? : — 1. the Campo- 

 deiform or Thysanuriform ; 2. the Eruciform or grub-form. 

 The first of these is the active form, with long legs (as a rule), 

 and well-developed, usually predaceous, mouth-parts ; this form 

 is considered the more primitive. Besides the predatory beetles 

 above alluded to, the first instars * of Stylopid^: and Meloid^; 

 are campodeiform. 



In 1869 Brauer first suggested that the larva? of a great number 

 of insects may be traced back to such primitive insects as Campodea 

 and Iapyoc, belonging to the order Thy san lira. He also pointed 

 out that most of the more highly developed insects assume another 

 larval form, which appears as a later acquisition, through adapta- 

 tion to certain definite conditions. In the case of Sitaris, Meloe, 

 and Epicauta we see the adaptation take place before our eyes. 

 This second form is the eruciform, grub-, or maggot-like larva. 

 Brauer rightly considers that this form resulted from the insects 

 living a stationary, semi-parasitic life on plants, in carrion, etc., 

 where they had no need to go far afield in search of food. The 

 majority of the Coleopterous larva? belong to this second division, 

 with greater or less modifications. 



There is, in many instances, a striking similarity among the 

 larva? of Coleoptera belonging to the same family, and this is not 

 only the case in those families in which the perfect insects bear 

 more or less resemblance to one another, such as the Carabid^e, 

 Staphylinid^e, Elateridjs, etc., but among groups in which the 

 imagines differ entirely in facies. This is particularly noticeable 



* Dr. Sharp adopts the term " instar," first proposed by Fischer (' Orthoptera 

 Europam,' 1853, p. 37) to express the form of insects at their various stages ; 

 hitherto there has been no such term in use, entomologists speaking of "the 

 form assumed at the first moult," and so on. If a caterpillar moults five times, 

 the chrysalis becomes the sixth instar and the perfect insect the seventh instar. 

 The adoption of this nomenclature saves considerable inconvenience. The 

 egg does not count as an instar, although there seems no reason why it should 

 not be r>o considered. 



