APHIDS INFESTING ECONOMIC PLANTS 389 
Keys to Species of Plant Lice Commonly Infesting Economic 
Plants in Region, Grouped Under Their Respective Hosts 
These keys are designed for the general entomologist, giving field characters 
such as location on plant, type of injury, color and woolliness of aphid in life 
but also including characters evident on the mounted specimens. The host plants 
are arranged alphabetically. Only viviparae are used in the key, unless other- 
wise stated. 
Aldereosee Birch 
Alfalfa (Medicago sativa) 
A.—Antenna longer than body; frontal tubercles well developed, exceeding vertex; 
body pale green. 
B.—Cornicle reticulated at tip. 
C.—Base of VI distinctly longer than tarsal II. (p. 300)..-2....22..2.....eeeceeeeeseeeeeees 
DS ben ree cee eee ae ee ae nl Rae ee The Alfalfa Aphid (Macrosiphum creelii) 
CC.—Base of VI about same length as hind tarsal II. (p. 324).......000..eeseeee 
eet te es Pree ens eect ree ee The Potato Aphid (Macrosiphum solanifolii) 
BB.—Cornicle not reticulated at tip, only imbricated. (p. 320)............2..-ce:cesseeeeeeees 
Bodonntaer sansesncaseorsntccect adcunsanvadensiatauidteddudeeaceaaicqisascstecuanacesectsnses The Pea Aphid (Macrosiphum pis1) 
AA.—Antenna shorter than body; frontal tubercles not well developed, not exceeding 
vertex. 
B.—Body black; sensoria on alata 4 to 7 on III, 0 on IV; cornicle 2 to 3 times 
length of hind tarsal II. (p. 151)........................ The Cowpea Aphid (Aphis medicaginis) 
BB.—Body green with black dorsal patch in alata, black speckles in aptera; 
sensoria on alata 25 to 30 on III, 3 to 7 on IV. Cornicle approximately equa! to 
hind starsal Tis (pi 124) ooo. -e see eseec The Short-beaked Clover Aphid (Aphis baker!) 
Alfilaria or Filaree (Erodium cicutarium) 
Body pale green; antenna-longer than body; cornicle not swollen, not reticulated, not 
longer than III; unguis .9 to 1.16 times as long as III; rostral IV+V .14 to .15 long, 
the same length as hind tarsal II; cauda twice as long as hind tarsal II. (p. 333)........ 
=p eagaece se See ee Se The Storksbill or Filaree Aphid (Macrosiphum zerozalphum ) 
Apple (Malus sp.), Pear (Pyrus communis) and Mountainash (Sor- 
bus sp.) 
A.—On bark primarily, secondarily on leaves and twigs; body brownish red, woolly; 
cornicle a mere pore; secondary sensoria annular; antenna not longer than half 
podyvErstorecwing, withomedia once-brancheds« (p.. S51) 2c -s coset cere cet cet cee cate ecae cee eeadee 
oath Schene  ce e  eD The Woolly Apple Aphid (Eriosoma lanigerum) 
AA.—On leaves and twigs, not on bark. Body usually green; not woolly; cornicle 
tubular; secondary sensoria circular (Fig. 00); media of fore wing twice-branched. 
Antenna longer than half body. 
B.—Cornicle hardly longer than hind tarsal II. 
C.—Body longer than 1.5; cornicle imbricated. 
D.—Black dorsal patch on abdomen of alata; rostral IV+V .10 long, 
not surpassing 2d coxa. (p. 124).................... The Clover Aphid (Aphis bakeri) 
DD.—Without dorsal black patch on abdomen of alata; rostral IV+V 
1 5S AONZ- ESUPDASSITIGE ZO CCONA PIE Poe Log) tetera arenes see ete ate row se kccee 
a a SS eo Rn A The Long-beaked Clover Aphid (Aphis crataegifoliae) 
CC.—Body not longer than 1.5; cornicle smooth (p. EY) Ee) Reh eee we 
OS ae SD Siete eRe The Leaf-curl Plum Aphid (Aphis helichrysi) 
