INSECTA OR HEXAPODA. 



123 



Insects commence their life in most cases as eggs or ova 

 produced by a female. Some have the power of giving forth 

 living young (viviparous), as we shall note in the Plant 

 Lice (Aphidse, &c.) In all insects the ovum gives rise to a 

 larva, this state being the period in which the insect grows. 

 Larvae of insects are known also as maggots, grubs, caterpillars, 

 and false-caterpillars. Caterpillar is a term applied to coloured, 

 often hairy larvje, provided with six true legs and generally 

 with four pairs of prolegs or sucker feet, in addition to an anal 

 pair (fig. 51, c). The number of these prolegs is sometimes 

 reduced to four or six (Geometers and Plusiadte), (a and d). 

 These fleshy prolegs enable the caterpillars to hold on to the 



.Fia. 01. — Larvae of Insects. 



A, Geometer larva ; b, Sawfly larva ; ij, typical Leijidopterous larva ; d, larva of 

 Plusia. 



vegetation they are feeding off. FaUe-caterpiUars are the larvoe 

 of the Sawfl-ies {Tenthredinidce) ; they have more than four pairs 

 of central sucker feet — usually the legs number twenty-two in 

 aU (b). Maggots are legless, fleshy larvaj of the Diptera or Two- 

 Winged Flies ; mainly dirty-white in colour, and tapering to a 

 point at the head end, blunt at the tail. Grub is the term 

 generally given to the larvae of some beetles (Weevils) and 

 Hymenoptera (such as Wasp grubs). In the larval stage the 

 insect feeds with great voracity. Several ecdyses take place, the 

 8kin splitting after stretching to a certain limit ; the larva ceases 

 to feed during this period of moulting. Frequently after each 

 moult, of which there may be four, the larva presents a different 

 coloration. The internal anatomy of the larva of insects that 



