Within-Field and Within-Panicle Distribution of Heliothis zea (Lepidoptera: Noctuidae) and Celama sorghiella (Lepidoptera: Noctuidae) Eggs in Grain Sorghum

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Abstract
The within-field and within-panicle distributions of Heliothts zea (Boddie) and Celama sorghiella (Riley) eggs were studied in Arkansas grain sorghum during 1985 and 1986. The distribution of eggs parasitized by Trichogramma spp. was also evaluated. None of the three insect species showed a consistent preference for any portion of a grain sorghum panicle based on either location (upper, middle, or lower third) or flowering stage (⅓, ⅔, or full bloom). H. zea exhibited a clumped within-field spatial pattern for total and parasitized eggs as based on Taylor's indices of aggregation ( a = 1.24, b = 1.31, and a = 1.85, b = 1.18, respectively). Total and parasitized C. sorghiella eggs were decidedly more aggregated than those of H. zea with Taylor's indices of a = 2.56, b = 1.46, and a = 3.28, b = 1.34, respectively. Required sample sizes needed to estimate population densities of both species are provided.