especially to shade and ornamental trees and young trees in plan- 
tations. Honeydew dropping from heavily infested shade and 
ornamental trees is often a nuisance as it forms a sticky coating 
on everything below, especially sidewalks, parked automobiles, 
and park benches. Additional damage may result from the growth 
of a sooty mold in the honeydew. It not only detracts from the 
esthetic value of shade trees and ornamentals, but also interferes 
with the proper functioning of their leaves. Numerous publica- 
tions have been issued on the identity, distribution, and hosts of 
aphids (296, 380, 583, 584, 585, 586). 
10. 
aL 
78 
Field Key to the Aphids, Based Principally on Host Plants 
Causing galls or gall-like formations .__ 2 
Not causing galls or gall-like formations _. Ace de Se 19 
On contters::2ye4ernekd ee ee oe Apia dog ds oh NT ed aT, Oy ted 
Onvhardwoodsi. = = ee ene ue Feet AliO 
On balsam fir twigs, branches, and ees causing 
“gouty” swellings at tips of twigs and stems, often 
causing leaves to turn red and trees to die. Insects 14 to 
114 mm. long; color dark brown to black, covered with 
white flocculence o.oo... «cb bide Se i Adelges piceae 
ON, SPEUCCs Sei td Belt sien Ba a eel etiah lence anes ee a 
Causing only terminal galls c or gall-like formations 
Causing galls other than terminal galls . 
Terminal galls, compact, small . 
Terminal galls, larger, composed of entire new growth 
with needles thickened at base, or loose and on current 
DRO Wil Menges ecw eectaleal eg ee tse eee eee we dxirke a part E Neste NOR iam 
Terminal galls conelike, compact; on new growth. On 
black, Engelmann, red, or Sitka spruce 
Pineus pinifoliae 
Terminal galls small, not conelike; on current year’s 
growth. On spruce, mostly red and black 
Adelges strobilobius 
Terminal galls comprising entire new growth and causing 
thickening of needles at base. On black and red spruce 
Pineus floccus 
Terminal gall a loose growth. On Engelmann, Norway, 
white, black, and red spruce .... oa... Pineus similis 
Causing galls on entire new growth of spruce host. On 
blue, Engelmann, oriental, and Sitka spruce 
Adelges cooleyt 
Causing pineapple-shaped galls only at base of new 
So CO O1}- 
growth of spruce 7 | | fae 9 
Galls with very short needles. On white and Norway 
spruce | Adelges lariciatus 
Galls with longer needles. ‘On white, red, and Norway 
spruce .... Adelges abietis 
On hickory or pecan, causing green, hollow, bullet-like 
galls on twigs or leaf stems in June 
Phylloxera spp. 
On other hardwoods lel: 
On elm fue 
On other hosts 15 
