62 THE CLASS OF IXSECTS. 



are gi-adnally released, and witli them tlie antennae, palpi, and 

 legs, and tlie larva removes itself entirely fi-om the shell and 

 membranes. In this })rocess of evolution the 3'oung 3Moe 

 throws off two distinct coverings : first, the shell with its lining 

 membrane, the analogue of the membrane in Avhich, as I have 

 elsewhere shown,* the j'oung Myriapod is inclosed, and re- 

 tained several days after the bursting of the ovum, and which 

 represents in the Articulata, not the allantois, but apparently 

 the amnion, of Vertebrata ; next, the first, or ftjetal deciduation 

 of the tegument, analogous probably to the first change of skin 

 in the Myriapod, after it has escaped from the amnion, and 

 also to the fii'st change which the j'oung Arachnidan inA-ariably 

 undergoes a few days after it has left the egg, and before it 

 can take food. This tegument, which, perhaps, may be analo- 

 gous to the vernix caseosa of Vertebrata, thrown off at the 

 instant of birth, is left by the young Meloe with the amnion 

 in the shell ; and its reparation from the body, at this earl}- 

 period, seems necessary to fit the insect for the active life it 

 has commenced." (Linn. Trans, xx. p. 306, etc.) 



The larva state. The larva (Latin larva, a mask) was so- 

 called because it was thought to mask the form of the perfect 

 insect. The larvae of Butterflies and Moths are called cater- 

 pillars; those of Beetles, grubs; and those of the two-winged 

 Flies (Diptera) maggots; the larA'se of other groups have no 

 distinctive common names. 



As soon as it is hatched the larva feeds voracious!}', as if in 

 anticipation of the coming period of rest, the pupa state, for 

 which stores of fat (th-e fatty bodies) are developed for the 

 supply of fat globules out of which the tissues of the new 

 bod}' of the pupa and imago are to be formed. 



Most larvai moult, or change their skin, four or five times. 

 In the inactive thin-skinned larvae, such as those of Bees, 

 Wasps, and Gall-flies, the moults are not apparent ; as the 

 larva increases in size it out-gTows the old skin, which comes 

 off in tliin shreds. But in tlie active larvie, such as cater- 

 pillars, grasshoppers, and grubs, from the rnpid deposition of 

 chitine in the outer layers of the skin, just before the change, 



* Philosophical Transactions, Pt. 2, 1841, p. 111. 



