Radiographic Studies of Angoumois Grain Moth Development in Wheat, Corn, and Sorghum Kernels1

Abstract

Daily X-ray radiographs were made of 73 wheat, 44 Corn, and 66 sorghum kernels to study (with little or no disturbance to the insects) development and behavior of larvae and pupae of Angoumois grain moth, Silolroga cercalella (Olivier), inside the kernels. Lengths of later stadia were generally ascertained, because time of molting to the penultimate and last instars usually could be determined. The ranges and means of the periods from hatching to penultimate instar were 8-33 days and 14.9 days in wheat, 9-28 and 13.9 days in corn, and 7-31 and 12.9 days in sorghum; the penultimate larval period was 1-10 and 5.3 days in wheat, 3-7 and 4.7 in corn, and 3-7 and 4.5 in sorghum; the penultimate larval period (including prepupa) 6-12 and 8.3 days in wheat, 6-10 and 7.9 in corn, and 5-8 and 6.4 in sorghum; pupal period 8-11 and 9.6 days in wheat, 7-10 and 8.9 in corn, and 7-10 and 9.3 in sorghum. Ranges and means of the total larval-pupal periods were 29-63 and 37.9 days in wheat, 28-52 and 35.3 in corn, and 25-54 and 33.0 in sorghum. Insects with longer developmental periods spent disproportionately more time as earlier instars than the insects with shorter developmental periods.