A Partial Life Table of the Cereal Leaf Beetle, Oulema melanopus,1in Northern Indiana2

Abstract

The study of the cereal leaf beetle, Oulema melanopus (L.), (Coleoptera: Chrysomelidae) was conducted in 1966 in 2 oat fields with different population densities in Indiana. The average number of eggs deposited per linear foot of row was 194 in the high-density field and 59 in the low-density field. All the eggs used to assess egg mortality in both study groups were 1 day old on May 20, when the study was begun. In the low-density field egg mortality from all causes was 60.3%. Predation by adults of the lady beetle Coleomegilla maculata (De Geer) and the convergent lady beetle, Hippodamia convergens Guérin-Méneville, was the primary biological factor causing egg mortality. The adults and larvae of these 2 coccinellids were also the primary biological agents responsible for larval mortality. Larval mortality from all causes was 72%. Prepupalpupal mortality was 42%. A total mortality of 93.8%, from day-old eggs to newly emerged adults, occurred in the low-density field Adults of the same 2 species of coccinellids were also the primary biological agents responsible for egg mortality in the high-density field. Egg mortality from all causes was 52.2%. Adults and larvae of these 2 coccinellids were the primary biological agents responsible for larval mortality, while rainstorm activity was the major physical factor. Larval mortality from all causes was 58.5%. Prepupal-pupal mortality was 54.5%. The total mortality in the high-density field, from day-old eggs to newly emerged adults, was 91.2%. Additional observations showed that larval mortality late in the season occurred when larval feeding depleted the food supply. Larval mortality caused by rainstorm activity in the high-density field following each of 2 rainstorms was 14.5 and 13.5%, respectively. Mortality of newly emerged adults in the high-density field ran as high as 2.8 per linear foot of row. This mortality was attributed to larval competition for a limited food supply prior to pupation, effects of high soil temperatures and low soil moisture during the pupal period, and lack of an immediate source of food and moisture for the adults upon emergence from pupae.