188 



attack and destroy other parasitic insects. These are 

 secondary or hyperparasitic, and they are of ten able greatly 



to lessen the good effects of tlie primary parasites. 



In the second manner of attack, certain insects 

 capture and devour Bodily others,; generally weaker and 

 smaller than themselves. The insect which obtains its food 

 in this manner is said to be predaceous in habit. Predaceous 

 insects are to be found in nearly all orders, being perhaps 



Fig- i77- Fiery ground beetle. 

 {a) larva; {b) adult insect. Natural size. {From U.S. Dept. Agric.) 



most numerous among the Coleoptera, although pond Hies, 

 lace- wing flies, certain thrips, many Hymenoptera, many 

 Hemiptera, some Diptera and Lepidoptera have this habit 

 of procuring food. Among the Lepidoptera it sometimes 

 happens when several caterpillars occur together as borers 

 in a limited space. Among the Orthoptera the predaceous 

 habit is found in the case of mole crickets, which devour 

 small insects which come within their reach in their under- 

 ground tunnels. Under certain conditions ants are of value 

 as natural enemies of other insects, especially when the 

 victims are out of their natural situation or are wounded 

 and thus unable to escape or defend themselves. Insects 

 which inhabit the soil are quickly attacked by ants 

 if exposed on the surface, and this suggests the practice 

 of ploughing or forking fields in which grubs and similar 

 insects are pests. 



PARASITIC FUNGI. 



Parasitic fungi of several species are known as natural 

 enemies of insects. Insects which are fixed in position 

 for considerable portions of the life-cycle, such as scale 

 insects and white fly, and those which have but little free- 



