METAMORPHOSIS. 



a second larval form, quite different from the first, dilated beneath 

 and adapted for floating on the honey, which it devours in about six 

 weeks. A few days later this second larva chauges into a short and 

 broad pseudo-nymph or pupa, sometimes called the first pupa, in 

 which state the insect passes the winter. In the spring a third 

 larva appears, like the second, but not dilated beneath ; this does 

 not eat, and soon changes into an ordinary true Coleopterous pupa, 

 from which emerges the imago. The triungulins of Melo'd are 

 very differently shaped from those of Sitaris, and have the legs 

 more strongly developed, but they are both equally adapted for 

 attaching themselves to bees. 



Dr. Sharp also quotes Professor Riley's account of the trans- 

 formations of a blister-beetle, Epicauta vittatu, which is parasitic 

 on locusts in North America. The triungulin campodeiform larva 

 is very active, and runs about on the ground in sunny weather, 

 examining the cracks, until an egg-pod of the locust is found ; 

 into this it eats its way and begins to devour an egg. After a 

 few days the triungulin changes into a Caraboid larva, and in 

 another week into a form like the larva of a Scaraband ; this grows 

 rapidly, leaves the egg-pod, and in a cavity close by turns into a 

 pseudo-pupa or coarctate larva, quite helpless and inactive, in 

 which form it passes the winter. In spring another Scarabaeid- 

 like larva emerges, which is somewhat active, but does not take 

 food ; in a few days this changes into a pupa of the ordinary 

 Coleopterous form, from which the perfect insect emerges in the 

 course of five or six days. 



The life-histories of several of these insects with various larval 

 forms or instars are more or less known, but they are very hard 

 to work out, and it will be a long time before we possess much 

 detailed knowledge of more than a few of them. In other 

 orders we have perhaps the most interesting case in Mantissa 

 (Neuroptera). 



Very little is known of the changes that take place in the 

 internal organs of any insects during the various metamorphoses, 

 although in the case of the Diptera the changes are con- 

 siderable. They do not appear to have been much studied in 

 the Coleoptera, but are probably of much the same character, 

 except that they are not so rapid, as in the Diptera. One thing, 

 however, we have learnt, and that is that " metamorphosis 

 is after all only an extension of embryonic life, the moults and 

 great changes being similar to those undergone by the embryo, 

 and that metamorphosis and alternations of generations are 

 but terms in a single series. Moreover, the metamorphoses of 

 insects are of the same general nature as those of certain worms, 

 of the echinoderms, and the frog, the different stages of larva, 

 pupa, and imago being adaptational and secondary" (Packard). 

 The processes by which the changes take place duriug meta- 

 morphosis are of two kinds : histolysis or breaking down, and histo- 

 genesis or building up, of tissue. The intermediary agents in the 

 former, according to {Sharp, Miall, and others, are " phagocytes 



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