Intraspecific Kernel-Entry Behavior and Competition among Larvae of the Angoumois Grain Moth

Abstract

The internecine activities of internal-feeding Angoumois grain moth larvae, Sitotroga cerealella (Oliv.), were studied by placing newly-hatched larvae with kernels (with or without pre-drilled holes) already infested, by placing 1, 2, or 4 larvae with each kernel (with or without holes), and by introducing 2 larvae/kernel in holes pre-drilled at different locations on the kernel. A larva placed with an infested kernel usually entered by the hole previously used. The second larva was usually killed or driven from the kernel by its original inhabitant. Two larvae introduced into predrilled holes in a wheat kernel intercepted each other faster when the holes were on opposite sides of the germ than when one hole was in the germ and one in the mid-kernel, and still slower when one hole was in mid-kernel and the other at the brush end. Two larvae could develop to maturity concurrently in one kernel with an aluminum foil barrier cemented between its halves. The Angoumois grain moth (Sitotroga cerealella (Oliv.), Family Gelechiidae) is a buff moth 13 mm long that usually oviposits among grain kernels. The eggs hatch in a few days and the newly-hatched larvae bore into kernels, or enter through cracks, and develop to adults inside the kernels. Duhamel and Tillet (1762) noted internecine activities among newly-hatched Angoumois grain moth larvae. They reported that M. de Reamur also had observed that phenomenon at least 20 years earlier. Others, including Crombie (1944 and 1946), reported competition of larvae for kernel-entry sites and also defensive behavior shown by established larvae as their tunnels were opened during dissections of infested kernels. This study obtained further details of intraspecific competition. Transactions of the Kansas Academy of Science, Vol. 72, No. 2, 1969. Published September 17, 1969. 1 Contribution No. 973, Department of Entomology, Kansas Agricultural Experiment Station, Kansas State University, Manhattan, Kansas, U.S.A. Supported in part by PHS Grant EF-114 and UI 095; Cooperative Agreement 12-14-100-8404(51) United States Department of Agriculture, Agricultural Research Service, Market Quality Research Division, Stored Product Insects Research Branch; and NSF Undergraduate Research Participation Grant GY-45. 2 Formerly NSF Undergraduate Research Participant (now with U.S. Naval Disease Vector Control Center, Alameda, Calif.); and Assistant Professor of Entomology, respectively.