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ARTHROPODS. 



hatched a larva (maggot, grub, or caterpillar), which lives a 

 life very dififerent from the adult, and is altogether unlike it 

 in form. The larva feeds voraciously, grows, rests, and 

 moults. Having accumulated a rich store of reserve 

 material in its " fatty body," it finally becomes for some time 

 quiescent as a pupa, nymph, or chrysalis, often within the 

 shelter of a cocoon. During this period there are great 

 transformations ; wings bud out, appendages of the adult 

 pattern are formed, reconstruction of other organs is effected. 

 Finally, out of the pupal husk emerges a miniature winged 

 insect of the adult or imago type. 



These insects are called holometabolic, i.e., they exhibit a 

 complete metamorphosis. 



The typical larva is the caterpillar with limbs and distinct 

 head ; the " maggots " of flies, etc. (without distinct head 

 or limbs), and the grubs of bees, etc. (with distinct head but 

 without limbs) are somewhat degenerate. But this larva of 

 holometabolic insects, technically called eruciform, is very 

 different from that of most ametabolic and hemimetabolic 

 insects, which is technically called campodeiform. For the 

 latter is not worm-like, but rather like one of the lowly 

 Thysanuran insects {Campoded), — with the regions of the 

 body well-defined, with locomotor thoracic limbs, and with 

 mouth-parts adapted for suction. 



The larvae of Insects vary enormously in habit and in 

 structure, and exhibit numerous adaptations to conditions of 

 life very different from those of the parent. Thus caterpillars, 

 which are usually plump and tense, so that a peck from a 

 bird's bill may cause them to bleed to death even if no 

 immediate destruction befall them, are protectively adapted 

 in many different ways. Their colours are often changed in 

 harmony with those of their surroundings, some palatable 

 forms are saved by their superficial resemblance to those 

 which are nauseous, a few strike " terrifying attitudes " 

 others are like pieces of plants. 



But for our purpose it is perhaps more important to recall the 

 differences between the respiration of some larvae and that of 

 the adult, between the apneustic larva of the dragon-fly, and 

 the holopneustic winged tyrant. Likewise of great importance, 

 and supplying a basis for classification, are the changes in 

 connection with the mouth-organs. The main facts may be 



