40 BULLETIN 746, U. S. DEPARTMENT OF AGRICULTURE. 
larva or a pupa unless it lias been injured in some manner. The 
damage produced by ants in increasing the number of mealybugs, 
and as sugar-house and household pests, more than offsets any good 
which may come from their destruction of insects. 
The Egg Parasite., Trichogramma minutum Riley. 
On account of its economic importance Trichogramma minutum 
(fig. 11) deserves more extended consideration. It is almost micro- 
scopic, and belongs to the large order of Hymenoptera, which in- 
cludes the bees and wasps. Under the microscope its wings are-found 
to be fringed with delicate hairs and to have lines of these hairs run- 
ning across their surfaces. 
The adults are about one-fiftieth of an inch long, with a wing ex- 
panse of a little more than the length of the body. On account of 
their minute size they are practically invisible in a sugar-cane field, 
even though they may be present in great numbers. The best way 
to find them is to search for a cluster of moth-borer eggs which have 
turned black (indicating parasitism). During the summer, and 
especially in the fall, an experienced person can sometimes find these 
clusters in considerable numbers on the leaves both of corn and of 
sugar cane. If the eggs are put in a small tube and observed for a 
few days, many light yellow Triehograrnma adults may be found to 
emerge. 
In the fields the females of these parasites search for moth-borer 
eggs very soon after emergence. Finding a cluster, the female in- 
serts her own eggs into the borer eggs, and in the course of eight 
days or longer, depending on the season, a new generation emerges, 
the parasites having developed from egg to adult within the moth 
eggs. 
The parasites are scarce at the beginning of the season, and in fact 
eggs destroyed by them were never found earlier than June 18 in 
Louisiana. As the season progresses they become more and more 
abundant, until at last they destroy almost every egg cluster of the 
moth borer. 
If the parasites could be so controlled that they would start their 
beneficial work earlier in the year, great good would result in lim- 
iting the ravages of the moth borer. Low temperatures retard the 
development of insects, and in an experiment to keep them over the 
winter parasitized eggs were placed in a refrigerator having a uni- 
form temperature of about 50° F. Some of the parasites emerged 
even at this temperature, however, and all of them died during the 
winter. 
Under natural conditions they undoubtedly hibernate in the cane 
trash left on the fields of the sugar plantations, at least until the 
trash is burned, when many of them are probably destroyed. This 
