26 THE LARVA. 



We are told that the grub of the beetle (oryctes-nasi- 

 cornis) sheds not only its internal skin, but also the 

 throat, and the inner lining of the large intestine, and the 

 stomach, change their skins at the same time. 



After each moult the larva appears weak and languid^ 

 and is covered with a liquid, while the entire body is ex- 

 tremely soft. A few hours' exposure to the air, however, 

 gives tenseness to the membranes, and it soon begins de- 

 vouring its food with a greater voracity than ever. 



A few larvte, however, such as those of the musca and 

 O'listruSf and also of the bees, wasps and ants, and proba- 

 bly many other hymenoptera^ do not change their skin 

 till they assume the pupa. 



The size and growth of larvse differ as widely as those 

 of the perfect insect. The larvae of some of the moths 

 [cossiis-Uffniperda) attain a size at least 72,000 times 

 heavier than when at first excluded from the e^^. The 

 stages of growth, however, except among those that do 

 not shed their skin, is not by gradual and imperceptible 

 degrees, as among other animals, but suddenly and at 

 stated intervals. The body does not increase in size from 

 day to day, but the parts become daily more tenso and 

 compact, until the enveloping skin is no longer capable of 

 containing them, when it is shed, and directly after the 

 moult, the body rapidly increases, so that we are scarcely 

 able to credit the possibility of its having been cased in so 

 small an envelope, e. g., it has been estimated that the 

 head of a silk worm that has recently cast its skin is about' 

 four times larger than before the change. This is partly 

 due undoubtedly to the unfolding of the parts that before 

 had been confined by the tenser covering. 



The larvse most remarkable for the rapidity of their 



