25 



State. Taking the acreage for corn in Illinois as 6,o8G,201, the 

 the number given in the report of our State Agricultural Department 

 for 188'2, an average loss in a year of as little as one bushel to 

 each ten acres would amount to about 658,6-0 bushels of corn, rep- 

 resenting at least $100,000 in money, an amount sufficient to pay 

 the expenses of a State Entomologist for fifty years. 



NOMENCLATURE. 



All those who have written upon the corn louse, with the excep- 

 tion of Prof, Forbes, have used without question the technical name 

 Aphis maidis. There can be little doubt, however, that the corn plant 

 louse belongs to the genus Ehopalosiphum, as this genus is used 

 by the great authorities on the classification of aphides. The char- 

 acteristic swollen cornicles are not as well marked as in some mem- 

 bers of the genus Ehopalosiphum, but will serve at a glance to dis- 

 tinguish this species from members of the genus Aphis. The old 

 name has so frequently appeared in these reports that a change is 

 not deemed desirable here. 



DESCRIPTION. 



JVinged viviparous female [root- form]. — Head black. Thorax brown- 

 ish black. Abdomen above pale green with about three marginal 

 black spots and numerous small, dark specks over the surface. 

 Antennae dark with pale at the articulations. Prothorax pale in the 

 middle ; meso- and metathorax chiefly brown. Cornicles black with 

 some black at their bases, chiefly inside. Cauda dusky, with several 

 transverse dusky marks before it. Thorax chiefly dark below, with 

 interspaces about bases of limbs brownish. Under side of the abdo- 

 men pale green ; two transverse dark marks before the cauda. Legs 

 mostly black; tibiiB for basal two-thirds pale. Length of body 1.8 

 mm. ; width of body, .9 mm. ; antennae, .7 mm ; cornicles, .12 mm. ; 

 wing, 2 mm. 



Pupa of winged viviparous female [root form]. — Head obscurely 

 dusky. Thorax obscure reddish brown. Abdomen above pale dull 

 green, without spots. Antennce dusky only at tip. Eyes reddish- 

 brown. Wing-pads obscurely dusky. Cornicles black. Cauda dusky. 

 General color below greenish. Eostrum dark at base and tip. Tarsi 

 and tips of tibiae dusky. Length of body, l.al mm. ; width of body, 

 .8 mm. 



Wingless viviparous female [root form]. — -Head black above. Pro- 

 thoracic segment black ; the following three body segments each 

 with a transverse dusky mark on their middles. Abdomen pale 

 green, with black marginal spots and with numerous smaller specks 

 over the surface. Antennae dusky at tip and slightly also at 

 base. Eyes reddish brown. Cornicles black. Cauda dusky; pre- 

 ceded by two transverse black marks. Abdomen beneath with two 

 transverse black marks before the cauda, otherwise nearly uniform 

 pale green below, Eostrum black at base and tip. Coxae, femora 

 chiefly, tips of tibiae and the tarsi black. Body widely oval in out- 

 line. Antennae short, about half the length of the body and head ; 

 first and second articles equal in length, first largest ; third article 



