314 Insect Pests. 



towards the rib and towards the leaf stalk. They take up their 

 position close together, almost touching one another at their head 

 ends, and they alternate with one another on each side of the mid 

 rib. As soon as they deposit a certain number of young they migrate 

 to another leaf. About fifty larvte are deposited on each leaf, and 

 these cling closely together in a broken row on each side. A few lice 

 may every here and there be found on the under surface of the leaves, 

 having been dropped by the female when crawling about. These soon 

 get to their proper quarters, and evidently entirely repudiate the aphis 

 custom of remaining on the under surface of the leafage." On the 

 17th of July, 1894, all the winged females disappeared, but left behind 

 them hundreds of their young. As a rule, fresh %vinged generations 

 soon make their appearance from those on the leaves, but contrary 

 notes I find in 1889, when only two winged generations were observed. 

 On the 1st of September the walnut aphis was still abundant in the 

 pupal form, but by the 24th of that month they had nearly all turned 

 to the M'inged generation, and had gone from the trees ; where to 

 could not be ascertained. There are several strange points in the life- 

 history, structure and habits of this aphis. As far as we know, every 

 one that hatches from the eggs whicli are deposited in the autumn 

 assumes the winged state before viviparous reproduction takes place. 

 Like Drcpanosi]plium platanoidcs, there is not known to be any wing- 

 less viviparous female. Unlike every other species of aphis, each 

 young one, a so-called larva, passes directly into the pupal state, and 

 then into the imago before any reproduction of species takes place. 

 This modified development is of great interest. Again, it has the 

 unusual habit of living upon the 'upper surface of leaves, and not, 

 as is the rule amongst plant lice, tipon the under surface. 



Desceiption. 



The pupa is long, oval, yellowish ; with pale testaceous head and 

 two rich reddish-brown irregular spots ; four spots on the prothorax. 

 Abdomen with four rows of dark spots, squarish in shape, so placed 

 as to form almost transverse bands — the middle pair of spots in each 

 segment are elongated and now and then almost unite, there is a very 

 small dark spot or dash above each spot in the central area — nine spots 

 in each central row with a vestige of a tenth in front, last segment 

 but one of abdomen with one large dot, nearly covering it; apex 

 slightly hairy. Eyes dark red. Antennte short, distal segments dark. 

 Eostrum very short, sometimes shorter than the head. Wing cases 

 prominent, pale yellow, edged with purplish-brown. Legs pale 

 yellow, tarsi dark and also the distal ends of femora in the posterior 



