60 BRITISH APHIDES. 



Winged (pspudo-) female. 



Inch. Millimetres. 



Expanse of wings 0-120 3*04 



Size of the body 0-045x0-015 1-14x0-38 



Length of antenna? 0-015 0"38 



Body greenish-yellow, fusiform. Abdomen tapering 

 towards the apex. Head broad. Eyes large and red. 

 Antennae rather short, third joint much the longest, 

 strongly ringed, and apparently without any marked 

 tubercle. Wings carried pentwise, membrane hyaline 

 and very delicate. Cubitus broad and yellow. Stigma 

 very faint. The three nervures pale yellow. 



The only specimen I have examined contained one 

 single large egg t measuring 0'015 of an inch. The 

 identity of species of these aerial and subterranean 

 insects is now too well-known to require comment ; 

 beyond the fact that Professors Riley, Balbiani, and 

 Cornu have all proved that the two kinds may be 

 compelled by artifice to change their habitats. The 

 apterous larva) taken from the roots, however, show 

 much disinclination to feed on the leaves, and probably 

 they never would raise the galls. 



Prof. Balbiani has shown that the appearance of the 

 winged insect is not necessary to complete the cycle 

 of life. In this case, when a recurrence to the male 

 becomes necessary, an apterous form must yield the 

 eggs which give rise to the sexes, just as it occurs in 

 the case of Phylloxera pimctata. 



The American Phylloxera appears to have as many 

 as six different periods for egg-laying ; but the Euro- 

 pean insect, from Lichtenstein's observation, would 

 appear to have fewer. The root-feeding larva) undergo 

 a hybernation, during which time they shrivel up 

 without losing vitality. In April they wake up, be- 

 come supple and inflated from the imbibition of sap, 

 ;m<l then it is that the chemical insecticides have the 

 greatest activity upon them. Extreme cold does not 

 much affect the ova of insects. M. Girard points out 



