INSECTA OR HEXAPODA. 125 



which becomes remodelled into the adult. This process is called 

 histolysis. The pupal stage, again, is very variable in length, 

 but not to such an extent as in the larva. There are often two 

 or more broods, or generations, of insects during the year ; in 

 some the summer pupal state only lasts a week 

 or so, whilst the winter pupal state lasts some 

 months. Insects pass the winter in all four 

 stages, many as ova, others as pupte, whilst 

 some hibernate in the larval and adult con- 

 ditions. 



Injuries are caused by insects both to plants 

 and animals. The damage is done in a variety 

 of ways, such as by eating the leafage, by tun- 

 nelling into the leafage, by boring into the 

 stems, even of the hardest wood. Both grow- ^ ,„ „ 



' ° Fig. 53. — Pupa ojf 



ing and stored grain and seed are attacked, tiphla oleraoea. 



,^ . .^ J r 4 w A • 1 (Slightly enlarged.) 



also fruit and culinary vegetables. Animals 

 are attacked by insects sucking their blood and by others with 

 parasitic habits, as exemplified by the Gad-flies and Warble-flies 

 respectively. Stored goods and provisions are also damaged. 



The senses of insects are of much interest to us, and well 

 worthy of our study. Sir John Lubbock's work on the ' Senses 

 of Insects,' which treats this subject most fully, shows that it 

 is one of some importance economically, as well as of deep 

 interest. That insects have the sense of smell well developed 

 we know for certain. "Whether the palpi or the antennae, 

 or both, are connected with this sense is not quite clear ; most 

 probably the antennae are chiefly functional in this respect. The 

 sense of vision is acute, as any one knows who has tried to catch 

 an insect settled on some flower ; whilst we cannot doubt that 

 taste is as surely present, when we consider the partiality certain 

 insects have for certain foods. 



To return once more to the changes through which an insect 

 goes — the so-called metamorphosis. Insects which pass through 

 the stages enumerated on p. 124, in which the larva is quite 



