133 



be done in England, I may briefly state that on account of the cooler 

 summers and milder winters and the lateness at which wheat is sown 

 in England there is very little danger, in my judgment, of any such in- 

 jury as we suffer from here, or as the insect causes in portions of con- 

 tinental Europe. In fact it is very injurious only under conditions 

 where two annual generations are pretty uniformly i)roduced, and I am 

 satisfied that in England, as a rule, ouly one generation will be pro- 

 duced. 



THE HOP PLANT-LOUSE. 



The nest insect which I will say a few words about is the Hop Plant- 

 louse [Phorodon humuU), of which we have been able to say for the first 

 time the past year that we now know positively its full life history. I 

 have for some years desired to settle a question that has been mooted 

 among entomologists, as also among hop-growers, viz, the mode of 



hibernation of the species ; for while some 

 of the earliest writers upon aphidology have 

 believed, and even stated, that there was a 

 form of this insect that occurred in autumn 

 on the Damson in Europe, the statement has 

 been as confidently controverted and the 

 fact denied by some of the highest author- 

 ities in the family. Hop-growers as a class 

 have generally j)ooh-poohed the idea. Yet, 

 from my own experience with other species 

 of the family and with their singular life 

 history and migrations from one plant to 

 another, I had for some time felt convinced 

 fk.so. Phorodonhiamdi. Biem-mother, tlmt PliorodoH liumuU also must havc some 



enlarged, head and antenna siill more 



enlarged (original). Other wlutcr resting placc than the hop vine, 



Fig. 31. Phorodon humuli, first migrant from plum, third generation, enlarged ; head at aide still more 



enlarged (original). 



