482 I 62 



DIFFERENCE OF FOOD OF THE LARVA AND THE PERFECT INSECT. 



In attemptiug to classify iusects according' to the nature of their food 

 we meet with a peculiar ditficulty, owing to the remarkable change 

 which some species undergo in this respect, in passing from the larva to 

 the perfect state. Most caterpillars, for exiunple, feed ui)ou leaves, 

 whilst the butterflies and moths which they produce sui)sist upon the 

 honey of flowers, or other liquid substances. Some two- winged flies 

 (AsiUdcv) feed upon the roots of plants in their lar^'a state, but become 

 eminently predaceous in their winged state. Another remarkable ex- 

 ample is furnished by certain coleopterous insects {Meloidce,) which are 

 parasitic in their larva state, but subsist upon foliage after they have 

 assumed the beetle form. The question therefore arises, to which stage 

 of the insect's existence shall the precedence be given in this respect ? 

 At first view it would seem that the perfect state ought to govern, but 

 when we take into account that insects are com])aratively short lived in 

 this state ; that having arrived at maturity they require but little food ; 

 and that some iusects take no food at all at this stage of their lives ; 

 whereas all the growth of an insect takes place A\'hilst it is in the larva 

 state, and consequently it is in this state that they feed so voraciously : 

 when we consider this, it seems more reasonable that in classitying in- 

 sects upon this basis, the food-habits of the larva should take the pre- 

 cedence. 



In the following work I have not thought it best to adopt any inflexi- 

 ble rule iu this matter, but have been governed by one or the other 

 view accordingly as its imj^ortance might seem to preponderate in each 

 particular case. 



DISTINCTION BETWEEN NOXIOUS AND INJURIOUS INSECTS. ' 



The terms noxious and iiyurious are often used indiscriminately, but 

 strictly si^eaking, iioxious insects are those which are endowed with 

 some poisonous or otlierwise hurtitd (juality ; and these are di\isible in- 

 to two classes accordingly as they are hurtful to mankind directly, sucli 

 as the mos(iuito, flea, and bed-bug ; or are Inirtful to the domesti- 

 cated animals, as the horse-fly, the bot-fly, and the various kinds of 

 animal lice. The insects which attack man directly are annoying rather 

 than seriously hurtful, and this is usually the case also with those which 

 molest the domesticated animals; but these sometimes nniltiply so as to 

 seriously imi)overisli the amimals which they infest. 



The term i>}jnrioiis, as distinguished from noxious, is i)ro]>er]y applied 

 to all those insects ^vhich damage numkind indirectly, but often to a 

 most serious extent by depredating upon those crops upon which 's\e de- 

 pend for subsistence and profit. 



