A SYNOPSIS OF THE APHIDIDAE 95 



dragon tree, cat-tail rush, and the banana. But the winter is spent 

 as viviparous females on the grains and grasses. 



This species has been confused many times with other species 

 infesting grains, such as Macrosiphum granarium (Kirby) and Tox- 

 optera graminum (Rond.). As the latter does not occur in this state 

 it cannot be confused here with Aphis avenue Fabr. Clarke listed this 

 as Nectarophora avenue Fabr., so it appears that he might have had 

 Macrosiphum granarium (Kirby) in mind, as it is highly improbable 

 that he could have confused Aphis av&nae Fabr. with a species of 

 Macrosiphum (Nectarophora). The cornicles of avenae Fabr., the 

 absence of antennal tubercles, and the irregular venation make it 

 quite easily distinguishable. The cornicles are quite short, as com- 

 pared with a species of Macrosiphum, and distinct antennal tubercles 

 are entirely lacking. The third discoidal vein of the forewing is 

 typically twice-branched, but the second is close to the apex of the 

 wing, and sometimes is entirely lacking. The only other species of 

 Aphis in this state with this character is Aphis salicicola Thomas, 

 found on willows. These two are readily distinguished from each 

 other by the comparative lengths of the cornicles, which are consider- 

 ably longer in salicicola Thomas than in avenae Fabr. 



112. Aphis brassicae Linnaeus 



Figures 203, 204 



Linnaeus, Syst. Nat., vol. 2, p. 734, 1735 (orig. desc.). 

 Clarke, Can. Ent., vol. 35, p. 250, 1903 (list). 

 Davidson, Jour. Econ. Ent., vol. 2, p. 302, 1909 (list). 

 Davidson, Jour. Econ. Ent., vol. 3, p. 376, 1910 (list). 

 Davidson, Pom. Jour. Ent., vol. 3, p. 399, 1911 (list). 

 Essig, Pom. Jour. Ent., vol. 3, p. 523, 1911 (desc.). 



Record. Cruciferae (various spp.) ; throughout California. 



During the late winter and spring cruciferous plants are often 

 heavily infested with this species. Of the cultivated plants cabbages 

 and radishes seem to be most heavily infested ; while the wild mustard 

 and radish often have the entire flower clusters covered with these 

 aphids. Oftentimes in the colonies of this species are also found 

 Aphis pseudobrassicae Davis, Rhopalosiphum lactucae (Kalt.), and 

 R. persicae (Sulz.). In southern California the colonies are always 

 attacked by the braconid fly, Diaretus rapae Curtiss, and a large per- 

 centage of the individuals destroyed. As summer comes on these para- 

 sites and such predators as syrphids and ladybirds usually get the 

 best of the aphids, which disappear to a large extent until fall. 



