236 



as already described. The assiduous industry with which the worker 

 ants will search every crack and cranny of old corn hills in spriug leads 

 me to think, however, that they may perhaps find there scattered plant 

 louse eggs, lost or overlooked in autumn. 



The ants, in the meantime, have continued their development in their 

 small and scattered colonies, the larvae beginning to pupate by the mid- 

 dle of May and the sexes emerging early in August. Just when and 

 where the eggs are laid by the fertilized female we have not yet deter- 

 mined, but specimens of this sex have been found in the earth, alive, as 

 late as Nov. 1, and the continual appearance of young larvai in the 

 home nests until the middle of the following summer shows that eggs 

 are laid, apparently by workers, at frequent intervals through the early 

 part of the season. 



The life history of the aerial corn louse, including its relation to the 

 root form, has proven a particularly refractory subject, and is not yet 

 complete. The connection of this form and the root louse as different 

 stages of the same species was assumed without proof by the early ob- 

 servers, and has not yet been experimentally demonstrated ; but, on the 

 contrary, a great number of attempts at demonstration havealraostcom- 

 pletely failed. The leaf louse has never been certainly brought out of 

 the root form, nor has the root louse been bred from the aerial form, 

 and the evidence of a connection between the two is indirect and cir- 

 cumstantial; while the proverbial difficulty of proving a negative, and 

 the fact that the annual origin of the aerial louse and the method of its 

 hibernation are both unknown make a present conclusion unwarranted. 



The winged root louse has been frequently taken on the leaves of 

 corn during the month of June — from the 9th to the 24th precisely — 

 and in the latter instances has been frequently found breeding there to 

 some small extent; but attempts to raise these young on corn or broom 

 corn, or to follow them in the field to the adult condition, have all thus 

 far failed. On the other hand, the first observed appearances of the 

 aerial louse (during the latter part of July) come after just about the 

 interval required by the hypothesis of an origin from the winged root 

 form. 



The aerial aphis grows much more freely on sorghum and broom corn — 

 especially the former — than on maize itself, but no experiments have as 

 yet been made with the transfer of the corn root louse to the leaves of 

 either of these plants. 



In our large cloth-covered breeding cages inclosing corn abundantly 

 stocked with root lice and ants, we have occasionally got an appearance 

 and temporary continuance of the root form on the stalks or leaves, 

 running up to a week with the usual production of young, and in two 

 instances, out of about thirty experiments tried, "aerial lice appeared 

 later on the corn plants thus inclosed. A possible source of error ap- 

 peared, however, in the fact that where the leaves of the growing corn 

 pressed against the cheese-cloth covering, winged viviparous aerial lice 



