Tenebrionidae

Darkling beetles or flour beetles are dark brown or black, not shiny, and they are usually slow-moving insects. These beetles are distinguished by the 5-5-4 tarsal formula, and notched eyes. They are primarily nocturnal, but many species are active during the day. Larvae are long, slender, and well sclerotized. They are scavengers on dead and decaying plant material. Several species occur in houses as accidental invaders, including Metoponium abnorme, Coniontis subpubescens, C. parviceps, and Blapstinus species. Neatus tenebrioides (Fig. 5.17c), is a large (10.5-14.5 mm long) species that occurs naturally under bark of dead trees and nests of squirrels and bumble bees, and also infests stored grain and cereals. The majority of pest species of tenebrionids are associated with stored foods.

Pest status is based on infestations of grains and cereals. Their presence in bird and mammal nests, in foods stored by small mammals, in caves, and in insect nests may predispose some of them to become pests in stored foods. Tenebrionids usually attack broken or damaged grains, because most of them cannot gnaw through the hard outer covering of whole grains. Food preferences for many species have not been determined, but the presence of mold or partially spoiled grain is often required for a sustained infestation. Many species live in wet and moldy habitats in nature. Pest species have been transported to all regions of the world.

Lesser mealworm, Alphitobius diaperinus (Fig. 5.18h) Adults are about 6 mm long and black or dark reddish brown. Full-grown larvae are about 20 mm long, brown to yellowish brown, and with pale bands on the margins of the sclerites. Eggs are deposited in batches of 4-12, and cemented to the surface with a clear secretion. At 32 °C, the daily oviposition rate is about six eggs per female, but the rate declines to four eggs per female at 38 °C, and one egg per female at 16 °C. Hatching is in 3-10 days; hatching success is 89% at32 °C, 80% ati6 °C, and 77% at 38 °C. Larvae do not develop beyond the first stage at

10 °C; larval survival is 60% at 320C, 52% at 38 °C, and 27% at 16 °C. There is a positive correlation between larval development and presence of the fungus Aspergillus. Full-grown larvae form a pupal chamber in food material; pupal period is 6-10 days. When infestations are severe, full-grown larvae move away from the food substrate to pupate, and tunnel into wood or other material. Adult life span at 21-24 °C is over 400 days. Development from egg to adult takes 42 days at 38 °C and 97 days at 15.6 °C. This species is cosmopolitan and is found with damp and moldy grain and cereal products. Larvae and adults feed on dead animals. This species is nearly cosmopolitan.

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