THE BIOLOGY OF LAEMOPHLOEUS FERRUGINEUS (STEPH.)

Abstract

Life history and morphological studies were made on Laemophloeus ferrugineus (Steph.), a coleopterous pest of stored grain and other products.Temperature greatly affected the rate of development of L. ferrugineus. At a relative humidity of 75%, eggs at 80° F. hatched in four to five days, at 90° F. in three to four days, and at 100° F. in two to three days. Similarly, the period from hatching of the egg to the emergence of the imago at 70° F. was from 69 to 103 days, at 80° F. from 26 to 38 days, at 90°F. from 19 to 33 days, and at 100° F. from 17 to 26 days. First instar larvae did not survive at a temperature of 110° F.An increase in relative humidity within the range from 50 to 75% accelerated development during the larval feeding period. Above 75% relative humidity there was no significant acceleration of development. Mortality was very high at relative humidities below 50%—all larvae failing to develop at a relative humidity of 25%. At 90° F. the period from the hatching of the egg to the emergence of the imago at 50% relative humidity was from 28 to 42 days, at 65% relative humidity from 23 to 33 days, at 75% from 19 to 25 days, at 90% relative humidity from 18 to 25 days, and at 100% relative humidity from 18 to 27 days. The optimum environmental condition for the development of L. ferrugineus was from 90° F. to 100° F. at a relative humidity of 75% or higher.L. ferrugineus populations increased more rapidly in whole rye and wheat grain than in the same materials when they were coarsely ground. Just the opposite was true in the case of oats, barley, corn, sunflower, flax, and soybeans. Whole kernels of rye, wheat, corn, and rice were decreasingly susceptible to injury in the order named, while whole kernels of oats and barley, and the seeds of sunflower, flax, and soybeans were practically free from injury by L. ferrugineus at humidity levels normally occurring in stored grains and seeds. Although first instar larvae did gain access to the wheat germ of grain described commercially as being "whole, sound, and undamaged", they were unable to successfully attack whole wheat kernels that had no breaks in their bran layers. The breaks need only to be microscopic in size to allow penetration by the larvae.