46 INSECT TRANSFORMATIONS. 



might devour them. The footstalks are so smooth 

 and slender that these grubs could not climb them, as 

 we have proved by experiment.* 



The ichneumon fly {Ophion luteum), whose larvae 

 feed upon the caterpillar of the puss-moth, also de- 

 posits eggs with a footstalk; and what is most singu- 

 lar, these larvae, after they are hatched, during the 

 first stage of their existence, continue attached to the 

 shells of their eggs. It is not till the puss has form- 

 ed her cocoon that they devour her, and spin their 

 own cocoons under its cover.| . 



The eggs of insects do not seem to hold any regu- 

 lar proportion, so far as regards size, with their parent 

 insects; for some large moths lay very small eggs, 

 while others of a small size lay eggs considerably lar- 

 ger. Kirliy and Spence think it probable that eggs 

 which produce females are generally larger than male 

 eggs; with the exception of the hive-bee, in which 

 the reverse takes place. Huber, as we have seen 

 above, tbund the eggs of ants of ditferent sizes, from 

 which he was led to discover that they increase in size 

 after being deposited. 



It has been remarked, that animals of prey are less 

 prolific than those which live on vegetable food; and 

 a similar principle appears to hold to a certain extent 

 amongst insects, the most prolific families belonging, 

 with few exceptions, to those which devour vegeta- 

 ble or animal substances beginning to decay and 

 putrefy. 



Thus it is that the eagle lays only two eggs, while 

 the wren lays eight, and the pheasant twenty-four ; 

 and in the same way the dragon-flies {LibelliiUna, 

 Mac Leay), do not lay above two dozen eggs, the 

 lace- winged flies [Htincrohidce) still fewer, and the 

 noontide fly {Mesembrina mcridiana, Me i gen) only 



* J. R. t See Insect Architecture, pp. 195 — 325, 6. 



