They infest boxes of stored, dried insects. The setae or “hairs” of Trogoderma larvae are important health hazards and are one of the reasons health and food regulatory officials are so concerned about infestations of these beetles. The setae are shed within the food product infested by the larvae and are present on the caste skins left behind after the larvae molt. The barbs and sharp hairs on the setae can be irritating to the mouth, esophagus and digestive tract of many people who might ingest the setae in their food. Irritation can also occur in the skin of persons contacting the larvae.
Biology and life cycle
Adult females lay up to 90 or more eggs within the infested food source and the larvae emerge to crawl through the food source and feed. The larvae are very active and crawl out of infested areas into adjacent areas to infest new food sources. The male larvae undergoes five molts and the female six prior to pupation. The pupal stage lasts about four to five days and the entire life cycle can be completed in as little as 45 days in warm temperatures.
Of particular interest is the light reactivity of this beetles as discovered by one researcher. The larva shun light and prefer the dark. Adult females only become attracted to light after egg laying is finished. Adult beetles can then be found in window sills and light fixtures.
Several members if the genus Trogoderma in the Dermestidae beetle family are important pests of stored food products as well as of fabrics and hides. Both the adults and larvae of Trogoderma are often difficult to distinguish from one another and generally require an entomologist strongly familiar with the taxonomy of these beetles.
The adult Trogoderma are small beetles ranging in size from 1/8 inch to ¼ inch (3 to 6 mm) depending on the species and the size of the larva is smaller due to poor nutrition, it will emerge as a smaller beetles. The beetles are oval in shape, are dark colored, and the wing covers will have varying patterns of brownish and yellowish scales. Other characteristics are used to distinguish between the species of Trogoderma adults such as eye margins and the shape of antennal cavities. Trogoderma larvae grow to about ¼ inch (6mm) in length and can be easily distinguished from other dermestid larvae such as the black and varied carpet beetles. The Trogoderma larva is a yellowish-tan color that is lighter than that of carpet beetle larvae. It also contains numerous stiff setae or “hairs” that emerge from the darker colored “plates” on the upper surface of the larva’s abdomen. A tail of numerous long thin hairs extends out from the tip of the abdomen.