How they perform the primary functions 



Fig. 28. In the family 

 Nemopteridae of the 

 Order Neuroptera, the 

 hind-wings are 

 exceptionally long 

 and narrow 



insects to the feeding of adults. Adult insects need food either to ripen 

 the eggs and sperm, or to supply energy for flight and other aaivities. 

 In addition the female has also to provide some kind of food supply in 

 the egg for the newly-hatched larva. 



The surprising thing is that adult insects vary so much in the food 

 they need. As a middle group, we might take the plant-bugs and the 

 beetles, where the adults live a hfe similar to, and amongst, their young. 

 At one extreme from this are the mayflies and some midges, which are 

 able to mate, and lay eggs — and to do so most proHfically — entirely on 

 the food-reserves that they accumulated as nymphs or larvae. At the 

 other extreme are such insects as mosquitoes and horseflies, the females 

 of which find it necessary to have a meal of vertebrate blood before they 

 can produce eggs that will survive. Finally, the tsetse flies all take blood, 

 male and female ahke. Now the tsetse is ovoviviparous, and keeps its 

 larva in a 'uterus' of the female until the larva is fully fed and ready to 

 pupate. The female, therefore, has to supply the entire needs of the larva 

 and pupa, as well as her own: but why does the male need blood too? 



Excretion 



The waste material to be disposed of comes from two sources. The 

 unused residue from the food material constitutes the faecal matter, 

 while the chemical waste from the body-tissues themselves — arising 

 from the breakdown and rebuilding of cells — is concentrated into urine 



47 



