124 
NOTES ON LIFE HISTORY AND HABITS OF APHELINUS. 
Mr. C. N. Ainslie made some observations on Aphelinus nigritus 
at Mesilla Park, N. Mex., in 1908. He states that when the adult is 
ready to oviposit it approaches an aphidid very slowly and cautiously, 
moving or swaying its body slightly from side to side and waving its 
antennae. When the antennae finally touch the plant-louse it stops, 
turns suddenly about, moves backward slightly, and then gives the 
victim a thrust with its hairlike ovipositor. This operation appar- 
ently causes pain to the aphidid, as she begins to "kick up" her 
abdomen and there sometimes appears a tiny drop of fluid where the 
puncture was made.' 
Fig. 33. — Dried remains of 
body of the spring grain- 
aphis from which adult 
Aphelinus nigritus 
emerged. Enlarged. 
(Original.) 
Fig. 32. — Aphelinus semiflavus, a parasite of the spring grflin-aphis. Greatly 
enlarged, a, Stigmal club, still more enlarged. (Original.) 
When the larva of Aphelinus nigritus is fully grown the body of the 
plant-louse, according to Mr. G. G. Ainslie, turns black and the legs a 
conspicuous white (fig. 33), while in individuals parasitized by A. 
mali these appendages are black. The body, however, of so small 
an aphidid as Toxoptera graminum appears to be but little swollen. 
Mr. C. N. Ainslie found that under favorable weather conditions A. 
nigritus developed from egg to adult in from 12 to 13 days. 
The following diagram will serve to illustrate the different hosts of 
Aphidius testaceipes, A. avenaphis, A. confusus, Aphelinus mali j 
A. nigritus j and A. semiflavus, which we have shown to attack 
Toxoptera graminum. This will give some idea of the numerous 
sources from which an army of parasites may be recruited to oppose 
any serious invasion of Toxoptera. 
