194 



APHIDES, SCALE INSECTS, ETC, 



with the eggs of other insects. It is found essential to 

 great amount of Locust presence that the eggs should 

 be healthy, and properly deposited ; that is, at the 

 proper depth below the surface, and otherwise in 

 favourable circumstances. The natural depth is an 

 inch or thereabouts below the surface ; it was found 

 that from eggs placed two inches deep, about a third 

 of the young Locusts managed to make their way to 

 the surface, but none came up from eggs buried m'>re 

 than two inches deep. Eggs hatched that were buried 



Fig. 15U. — Locust. 



as much as twelve inches deep, and the young Locusts 

 worked their way for an inch or two through the 

 earth, but (as we just observed) did not come up to 

 the surface; and at the time when these were hatched, 

 eggs buried deeper than twelve inches were still 

 unhatched. 



It is further noticed that eggs placed deeper, though 

 they remained unhatched whilst buried, were not 

 harmed by lying underground, for on being brought 

 to the surface they hatched at once. Further, it was 

 found, with regard to the effect of warmth or of cold 

 in hastening or retarding hatching, that the Locust 



