PHORODON HUMQLI. 
167 
Pale green. Lighter underneath. Antennae about 
equal to the body, green at their bases, tips brown. 
Head and band on prothorax dark brown. Thoracic 
lobes, one or more cross stripes on the abdomen, and 
four spots on each edge, black. Anal plate black. Oor^ 
nicies green. Legs with brown femoral and tibial joints. 
Tail pale. Wings ample, cubitus and stigma greenish 
yellow. Other veins pale brown. The peculiar cha- 
racters of the frontal tubercles are less marked in 
the winged females. 
Winged male. 
Indies. Millimetres. 
Expanse of wings 0*200 b'OS. 
Size of body 0*045x0*020 1*13x0*50. 
Length of antennae 0*070 1*77. 
,, cornicles 0*010 0*25. 
Less bulky in form than the winged female. An- 
tennae and wings very long. Head and thorax much 
developed. Abdomen attenuated. Colour wholly 
pale green excepting the thoracic lobes and scutellum, 
which are olive. The frontal tubercles are prominent 
and thrown forward. Wing-veins as in the winged 
female. 
Taken in the middle of October on the hop plant. 
Walker says that P. Immidi migrates in early spring 
from the sloe, Frunus sjpinosa^ to the hop plant, and 
again leaves the hop in autumn to go back to the sloe ; 
indeed, he says this migration may occur more than 
once in one season. He believes that the two Aphides 
infesting these dissimilar plants are really identical. 
Passerini in commenting on this subject says, it is 
hard to comprehend that such a cause, viz. an alteration 
of food, can produce an organic change of such conse- 
quence as the absence of the tooth on the frontal 
tubercle. He argues that the existence of the genus 
Phorodon depends chiefly on this characteristic, and 
as his {Italian) specimens from Prnnus sjpinosa all 
