SYNOPTICAL KEY TO THE APHIDIDAE OF MINNESOTA I3I 
51. Group TOXOPTERA. In a more strict classification the fol- 
lowing genera would be arranged with the preceding group, but it is 
more practical to consider those genera separately that differ greatly 
in some one character which at once distinguishes them from the 
ordinary Aphis. Such aberrant characters are a reduction in venation, 
- antennae, or tarsi. The following genera are known from Minnesota: 
a. Media of forewings with only one branch........ Genus TOXOPTERA 52 
b. Hind wings with only one oblique vein....... Genus HYSTERONEURA 53 
ce. Tarsi of all the legs reduced and without claws..Genus MASTOPODA 54 
52. Genus TOXOPTERA Koch, 1857. Type: Aphis aurantiae 
Boyer, 1841. Media with only one branch in the fore wings; cornicles 
cylindrical and moderately long; cauda Aphis-like; sensoria on the 
antennae in small*number. 
(60) TOXOPTERA GRAMINUM (Rondani) Passerini, 1860 
This southern grain aphis is at times quite common. 
53. Genus HYSTERONEURA Davis, 1919. Type: Siphonophora 
setariae Thomas, 1878. Aphis-like in characters, but the hind wings 
have but one oblique vein; sensoria on the antennae in small number. | 
(61) HYSTERONEURA SETARIAE (Thomas) Davis, 1919 
This red-brown species is rather common on plum, migrating to 
various grasses for the summer. 
54. Genus MASTOPODA Oestlund, 1886. Type: Mastopoda 
pteridis Oestlund, 1886. Antennae with only five segments, the third 
and fourth connate; cauda short and cone-like; tarsi reduced to a 
small mamma-like joint without claws. Found on fern. 
(62) MASTOPODA PTERIDIS Oestlund, 1886 
Found on Pteris aquilina; a comparatively rare form. 
55. Division CLAVICORNIA. Koch placed all aphids with 
swollen cornicles in the genus Rhopalosiphum; it has since been found 
that swollen cornicles are present in many of the tribes of the family 
and that the character is more than generic. Koch’s Rhopalosiphum 
has therefore been broken up into numerous genera, some of which 
belong to the division Clavicornia of the tribe Aphidini. The division 
‘includes those genera that are Aphis-like, but with distinct swollen 
cornicles. The following genera are found in Minnesota: 
a. Cornicles swollen on the apical half; cauda slender... .............5-000- 
Genus RHOPALOSIPHUM 56 
b. Cornicles slightly swollen in the middle; cauda stout.................-06- 
Genus SIPHOCORYNE 57 
c. Cornicles strongly swollen in the middle.......... Genus LIOSOMAPHIS 58 
