Natural Control of Eggs and First Instar Larvae of Heliothis armigera1

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Abstract
Certain of the biological factors affecting the eggs and 1st instar larvae of the cotton bollworm, Heliothis armigera, and their relative importance were studied at 3 cotton-growing locations near College Station, Spur, and Waco, Texas, during 1932, 1933, and from 1938 through 1940. The standard method of determining the probable infestation of this insect by counting eggs on about the top 6 inches of the main terminal of the cotton plant was used. Eggs and larvae were located, labeled, and observed as much as possible until their fate was known. The % of the 1938 tagged eggs that were known to have hatched during the 6 yrs. ranged from 26.4 to 58.1. Failure of eggs to hatch due to parasitization ranged from 1.2 to 15.2%; due to predators from 15.3 to 32.9%; and due to unknown causes and dislodging by wind, rain, and cultivation from 11.2 to 43.7%. Results of observations on 814 lst-instar larvae showed that in 4 of the 6 yrs., > 1/2 were lost due to wind, cultivation, and other causes. The % of larvae destroyed by predators, especially Orius insidiosus, ranged from 12.6 to 59.6. It is concluded that not more than 61% of the eggs laid by H armigera develop beyond the 1st instar under field conditions.

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