Variation in Populations and in Size of Adults of Trichogramma Minutum Riley Emerging from Eggs of Heliothis Obsoleta Fab.

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Abstract
In rearing adults of Trichogramma minutum Riley from eggs of the corn ear worm moth (Heliothis obsoleta Fab.) on corn during 1929, it was observed that the population of these parasites per host egg was variable and that there was considerable variation in the size of the adult parasites, possibly because some of these were depauperate. Collections of parasitized Heliothis eggs have been made since that time during periods of high parasitization and the adult parasites have been reared, and, in some instances, the forewings of these adults measured to determine the extent of their variation. The collections described herein were made in the following localities: Richmond, Va., in the summer of 1929 (292 Heliothis eggs); Savannah, Ga., in 1930 (400 eggs), and in June, 1933 (1,000 eggs); and in Sandersville, Ga., in September, 1933 (308 eggs, from soy beans). Parasites emerged from these 2,000 eggs, and in the first, third, and fourth collections (represented by 1,600 eggs) the forewings of each of the emerged parasites were measured. The Heliothis eggs were segregated individually in shell vials 25 by 5 mm. in size, cotton-plugged. After emergence, the parasites from each egg were mounted on a microscope slide, and the length of the forewings of each was measured by means of a micrometer eyepiece.

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