412 
Journal of Agricultural Research 
Vol. XXIV, No. s 
One came from a larva determined before its death as and 
the others all from mixed larvae specifically undetermined. It is therefore 
unknown whether this parasite is limited to the single host or divides its 
attentions between the two. Further rearings are necessary to settle this 
point. The mature maggots of this species almost invariably issued 
from their host while it was still a larva and from one to three days after 
its death, leaving only an empty head shell and a shriveled skin. The 
adult flies appeared from ii to 19 (average 13.5) days after pupation. 
The eggs are white and conspicuous and are attached to any part of the 
host, most frequently about the thoracic segments. As many as 14 eggs 
have been seen on one individual, but it seems very unusual for more than 
one of the parasites to reach maturity, at least on a host of this size. 
In the one such case observed both of the two flies appearing were very 
small and one failed properly to expand. In fact, this fly does not seem to 
have the vigor of Exorista nigripalpisj for, although reared under exactly 
similar conditions, nearly half of them failed properly to expand their 
wings upon emergence, and some failed even to free themselves from their 
puparia. Several of the crambid larvae which yielded these flies did not 
have eggs on them when collected, but the shells had probably been 
molted off after maggots had hatched and entered their host. 
Only a single fly of the species Exorista nigripalpis Towns, was reared 
from a larva previously determined as mutahUis^ and as a considerable 
number were obtained from larvae known to be trisectus this parasite is 
discussed in a forthcoming paper dealing with trisectus. 
The writer has records of two species of hymenopterous parasites 
attacking Cramhus mutahUis, 
Apanteles cramhi Weed has been recorded from other species of the 
genus, and recently (10, p, ^46) from mutahUis from South Dakota and 
Tennessee. When full-grown the grubs of this parasite emerge from 
their host and spin a mass of white cocoons near by. The host remains 
alive for several days, but finally dies without moving or feeding. The 
adult parasites emerge in six or seven days after the cocoon is formed. 
Macrocentrus crambivorus Vier. has been reared twice from larvae of 
Cramhus mutahUis at Nashville, Tenn. In both cases the host larvae 
were nearly full grown but appeared abnormally pale when collected. 
In the rearing box each constructed a silken case, and when this was 
examined a little later the larva had been replaced by a dense mass of 
elongate yellowish brown cocoons, 20 or 25 in number. The following 
day the white pupae could be seen indistinctly through the cocoons. 
The parasites became adult and active within their cocoons eight or nine 
days later, but their actual emergence seemed to be entirely dependent 
on proper conditions of humidity. In one instance the adults, although 
active within the cocoons, did not emerge until the stopper of the vial 
was moistened, whereupon they all released themselves within five 
minutes. Other groups behaved in the same way unless they had been 
so long confined to their cocoons that they were unable to emerge at all. 
The adults are slender, yellowish brown in color, and very active. The 
females trail a long threadlike ovipositor behind them. In the writer’s 
rearings all those emerging from a single mass of cocoons were of one sex. 
Others, also apparently of this species (determined by S. A. Rohwer as 
Macrocentrus sp.) were reared from two of the undetermined larvae taken 
at Ta Fayette, Ind., in June, 1920. One yielded 14 males and the other 
29 females. 
