Most recently reviewed by: Pat Porter (2018)
Common Name(s): Khapra beetle, Warehouse Beetle
The warehouse beetle, Trogoderma variabile, is one of several species of beetle in the genus Trogoderma that are considered pests of stored products. It is the most common Trogoderma pest in homes. The warehouse beetle is oblong to oval, 1/8 to 3/16 inch long, with a dark and light mottled pattern on their wing covers. Adult Trogoderma are fairly short-lived and rarely feed on stored products. However, they are considered excellent fliers and can disperse quite easily.
Warehouse beetle immatures are cigar-shaped and hairy. Trogoderma larvae have hastisetae, which appear as darker or longer clumps of hairs, and arise directly from the tops of the plates on the last three abdominal segments. These hastisetae can cause gastrointestinal problems if ingested by humans.
It should be noted that the warehouse beetle is a close relative of a highly destructive and tightly quarantined pest called the Khapra beetle Trogoderma granarium. Khapra beetle also known as cabinet beetle is considered one of the 100 worst invasive species in the world. Because of their warm climates, the Khapra beetle has the most potential for establishment in Arizona, California, Kansas, New Mexico, Oklahoma and Texas. The Khapra beetle is a destructive pest of stored grain and other dried plant—as well as animal—products. It is able to survive almost anywhere in storage facilities that are protected from cold environments. This pest is known for its “dirty eating” behavior; by feeding only a little on each grain, one tiny beetle can damage a surprising amount of stored product. If you suspect you have a Khapra beetle you MUST contact the United States Department of Agriculture, Animal and Plant Health Inspection Service in your area.
Origin and Distribution
This beetle feeds on a wide variety of foods including cereals, candy, cocoa, cookies, corn, corn meal, fish meal, pets foods, flour, nets, dried peas and beans, potato chips, pastas, spices, dead animals and dead insects. The warehouse beetle occurs throughout the United States and is common in seaports throughout the world.
Habitat & Hosts
When food becomes scarce or disappears, Trogoderma larvae may enter a lengthy period of inactivity known as diapause, where insects are completely inactive and do not feed. When larvae break diapause, they can resume infesting food items. This ability to diapause in the absence of food combined with the ability to chew through packaging can make control of Trogoderma beetles difficult.
Females lay around 90 eggs in a lifetime, and the resulting offspring go through a life cycle that takes anywhere from two to four months to complete. In cases of food shortages or poor environmental conditions, warehouse beetle larvae can slow their development by molting numerous times before deciding to pupate.
ManagementIf you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.
Warehouse beetles are among the most difficult indoor pests to control because of their ability to find food in obscure places and to disperse widely throughout a building. Successful control depends on a combination of sanitation and exclusion. If exclusion and sanitation are successful, insecticide treatments aren’t required.
When warehouse beetles threaten products in commercial warehouses or storage areas, a monitoring program using sticky traps baited with an appropriate pheromone is recommended. Sticky traps can also be used in homes where infestations are serious. Traps placed throughout a building can show where beetles are coming from; the traps are also useful for monitoring the effectiveness of control practices. Check traps once or twice a week. You can also use pheromone traps to augment other control methods if you use them to attract adult males in small confined areas. Sticky traps are also available without a pheromone; you can place these traps on windowsills to trap adults that fly to windows.