302 ANNUAL REPORT. 



subject. Allow me to make a suggestion as to how this mode of life may possibly 

 have been acquired in the family. Ants are known to be very fond of plant-lice on 

 account of the sweet fluid or honey that they emit from the honey-tubes. They 

 are also known to take very good care of them, to protect them from enemies as 

 far as possible, and to remove them to a place of safety if they are much threatened, 

 it is therefore probable that in time the ants also brought them down under ground 

 into their own habitations for protection, and accidentally finding that they could 

 here also have suitable food from the roots of the plants, the first step was taken 

 towards the domestication of the plant-lice by the ants. These domesticated spe- 

 cies would necessarily change considerably in time and are now found as distinct, 

 probably making it a very difficult matter to trace them from their original stock. 

 We cannot presiime that whole species were transformed into a root inhabiting 

 but a part must have continued as aerial. Tnese subterraneous plant-lice would 

 therefore, not be a dimorphised form, but a dimorphised species, if we may use the 

 expression, of some aerial species. But it is not my intention to enter more fully 

 into this subject of dimorphism this evening, how interesting it yet might be. If 

 I can onlj' in some degree call your attention to this subject for future observation 

 by showing that even in this much neglected and little attractive family of plant- 

 lice, we yet have gome of the most interesting problems of insect life, enough has 

 been said. 



During last fall I had the good fortune to find the eggs of several species that 

 probably will be worthy of mention. Of the higkest genus they were observed in 

 three cases. 



SipJioTicpliora frigida', Thos. — Found on the ragweed (Ambrosia irifida, L.) As 

 only a few eggs were found on any on^ plant, I am still in some doubt if they are 

 usually deposited on the plant, or in some other place. On dissecting the oviparous 

 form eggs were always found. 



Siphonophora frigidm, Oest. — This species, as noticed above, deposit the egg? on 

 top of the branches of the plant they inhabit [Artemisia frigida, Wild.) When first 

 laid they are soft and pale in color, but soon become hard and shining black on 

 exposure to the air. By the hardening of the viscid substance that covers them at 

 first, they become closely cemented to the plants, where they remain over winter. 



SiplionopTiora adianti, Oest. — A species inhabiting one of the ferns {Adiantum 

 pedatum, L.,) was observed to deposit the eggs on the under side of the fronds, and 

 as these remain attached to the root-stalk over winter, the young larvae will have 

 no trouble to find the new growth, which springs from the same root-stalk the 

 following year. 



Myzus potentillae, Oest. — A species that is closely related to the currant aphis, also 

 deposit the eggs on the underside of the leaves of the plant on which they live, and 

 as these, like the foregoing, remain over winter, their larv* are as well provided 

 for. 



Aphis mail, Fitch. —The apple tree aphis is well known to deposit the eggs on 

 the trunk and branches of the apple tree. All the trees observed from this locality 

 are well stocked with eggs for next summer. The eggs were mostly deposited 

 (luring the month of October, though some as late as November. They are of a 

 dirty green color when first laid, but soon become shining black. 



The extensive genus Aphis has so far given the greatest trouble in tracing the 



