210 TRANSACTIONS OF THE ILLINOIS 



A SYNOPTICAL TABLE OF THE GENERA MENTIONED, ARRANGED ACCORDING TO THE 



SCIENTIFIC CHARACTERS. 



I. Saltatorial ; antennre, with two bristles at the tip. 



a. Antenna; longer than the head and thorax, neither the first nor second joint 



elongated ; head slightly cleft in front. — Psylla. 

 aa. Antennae short ; first joint elongated ; head rather deeply cleft in front. — 



Dirapkia. 

 II. Non-saltatorial ; antennae not tipped with two bristles. 

 A. Abdomen furnished with honey-tubes ; third discoidal veins of the fore wings 



twice forked. 



b. Honey-tubes never reduced to mere tubercles ; found chiefly on leaves. — 



Aphis, 

 bb. Honey-lubes reduced to mere tubercles; chiefly found on limbs, twigs or 

 stems ; abdomen usually (not always) with transverse rows of dots. — • 

 LacJmus. 

 A A. Abdomen without honey-tubes or tubercles ; third vein of the fore wings only 

 once forked, simple, or obliterated; or wingless. 



c. Some individuals acquiring wings ; never residing wholly underground. 



d. Wings erect in repose. 



e. Third vein simple. — Eriosoma. 

 f. Legs and antennse of moderate length ; latter more than five-jointed ; body 



not broad and flat. — Pemphigus, 

 ff. Legs and antennce very short ; latter but five-jointed ; body broad and flat. — 



Adelges. 

 dd. Wings horizontal in repose. 



p. Third discoidal vein of the fore wings once forked. — Thalaxes. 

 gg. Third discoidal veins of the fore wings simple or obsolete; hind wings with 

 an angular point on their outer margin. 

 h. Hind wings with one discoidal or branch vein ; antennae three to five- 

 jointed. 

 i. Females become stationary and die without extruding their eggs ; third 

 discoidal vein extends to the tip of the wings ; antennas four or five- 

 jointed. — Chermes. 

 ii. Females deposit their eggs (?) ; third discoidal vein sub-obsolete, not 

 running to the lip of the wings; antenna; three to five-jointed. — 

 Horinaphis. 

 hh. Antenna three-jointed; hind wings with no discoidal or branch vein. — 



Phylloxera, 

 cc. Never acquiring wings (so far as known) ; living wholly underground. — 

 Rhizobitis. 



It is not claimed that this table is more than approximately correct ; it is given 

 simply as one means of aiding in determining species. The genera Phopalosiphufti and 

 Siphonophora are included under Aphis as subgenera. 



ADDENDA. 



Since the foregoing was written, I have succeeded in obtaining a brief synopsis of 

 Passerini's arrangement of the Aphidse, which is as follows : 



APHIDID.E, Passerini.— (Tribes.) 



A. Antenna; seven-jointed. — (i) Aphidin^. 

 AA. Antenna; six-jointed, at least in the winged form. 



