T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Beetle (Lesser mealworm) Alphitobius diaperinus

Kingdom:   Animalia
Phylum:     Arthropoda
Subphylum: Hexapoda
Class:        Insecta
Subclass:  Dicondylia
Infraclass:  Pterygota
Superorder:  Neoptera
Order:       Coleoptera
Suborder:  Polyphaga
Infraorder:  Cucujiformia
Superfamily:  Tenebrionoidea
Family:      Tenebrionidae
Subfamily:  Tenebrioninae
Tribe:  Alphitobiini
Genus:      Alphitobius
Species:     A. diaperinus
Binomial name: Alphitobius diaperinus
Synonyms:  Tenebrio diaperinus, Phaleria diaperinus, Uloma opatroides, Uloma mauritanica, Alphitobius
auritanicus, Heterophaga opatroides, Heterophaga diaperina, Alphitobius diaperinus.
Common name: Lesser mealworm, Litter beetle

Alphitobius diaperinus is a species of flying beetle in the family Tenebrionidae, the darkling beetles. It has a cosmopolitan distribution, occurring nearly worldwide. It is known widely as a pest insect of stored food grain products such as flour, and of poultry-rearing facilities. This beetle inhabits poultry droppings and litter and is considered a significant pest in the poultry industry.
It is a vector of several poultry pathogens and parasites. It is suspected to be a health risk to humans in close contact with larvae and adults.
The adult lesser mealworm beetles are roughly 6 millimetres long and are widely oval, moderately convex, shiny black or brownish-black. The colour is variable among individuals and changes with age. Much of the body surface is dotted with small dot like indentations. The elytra (hardened forewing) have shallow longitudinal grooves. Adults can live three to twelve months, with females continuing to produce eggs most of their life at one to five day intervals. After mating, a female beetle usually lays up to 400 eggs but it can produce many more. The eggs are narrow, whitish or tan, and are about 1.5 millimetres long.  
It takes up to 7 days for the larvae to hatch. They are at first whitish when newly and then darken to a yellow-brown colour. There are approximately six to 11 larval instars. The larvae are segmented, with three pairs of legs toward the front end. They become adults in 40 t0 100 days depending on conditions  and are approximately 7 to 11 mm in length at last instar.

Alphitobius diaperinus mealworms can also cause poultry house structural damage. When searching for suitable pupation sites, larvae will chew holes in wood, fibreglass and polystyrene insulation panels in the walls of poultry houses. Energy costs in beetle-damaged broiler houses are reported to be 67% higher than in houses without beetle damage (Geden and Hogsette 1994).

The beetle stage of Alphitobius diaperinus

A lesser mealworm with adult beetle in background.

The last larval instar.