FSYCHE. 



THE HIBERNATION OF APHIDES. 



BY CLARENCE M. WEED, DURHAM, N. H. 

 fAnnual address of Ihe retiring president of the Cambridge Entumological Club, 14 February. 1S46,] 



In hititudes where winter is a period ndopt to pass the winter. The noiinal 

 of pi'otracted cold, a siiccessfnl mode ot life-iiistory of these little creatines may 

 passing through it is of first importance be briefly summarized as follows. In 



the spring there iiatches from an egg 



to all animals that cannot follow the 

 swallow with the changing season. 

 .Such creatures must not only endure 

 the low temperatures to which they are 

 subjected, but also must 30 protect them- 

 selves that a certain proportion of them, 



deposited the autumn previous, a little 

 aphid that sucks the sap of its food 

 plant for a number of days — sometimes 

 a fortnight — before it becomes full- 

 grown. During this period of grovvtii. 



at least, shall escape the attacks of tlie it molts or sheds its skin a number of 



various enemies that are abroad during times to provide for its rapidly increas- 



this long period of forced inactivity. ing size. This insect is sometimes 



With insects successful hibernation is called the stem- mother. She is ahva) s 



of vital importance, and each species wingless. Soon after reaching maturity 



appears to have chosen (largely through she commences to give birth to living 



the action of natural selection) the salcst young, continuing the process usually 



method of passing through. A- vast lor several days. These young are 



number of them hibernate in the egg most commonly born naked, but in 



state ; man)- in the larval state ; man\' 

 as pupae ; and a considerable propor- 

 tion as adults. Not infrequentlv the 

 same species may hibernate in two or 

 more of these conditions. In such cases 

 it is evident that if the insect in one 

 stage suffers more loss than in the other, 

 the latter — other things being equal — 



some species thev are surrounded by a 

 thin pellicle which ruptures soon after 

 birth. They resemble the stem-mother 

 in general appearance, being of course 

 much smaller. Each soon begins suck- 

 ing sap on her own account, and in the 

 comse often days or a fortnight becomes 

 mature. It then beirins bringing other 



will gradually replace the former as the aphides into the world : these soon 



hibernating condition. mature and give birth to a third gener- 



The aphides furnish an interesting ation. All of the individuals of these 



illustration of the various methods the early broods are parthenogenetic females 



different species of a single family may giving birth to living young without the 



