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


Beetle (Darkling) Amarygmus spp

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Coleoptera – Beetles
Family: Tenebrionidae - Darkling Beetles
Species: Amarygmus sp
Common name: Darkling beetle species

This an Australian beetle. In Watts 1992 Tenebrionidae catalogue states it is found around Auckland under bark and logs and has since been found it at Ohope and New Plymouth so it is probably now widespread in the warmer parts of the North island and may be spreading south.

Tenebrionidae are one of the most numerous and diverse families of beetles, with a world fauna of many thousands of species. The New Zealand fauna is relatively large and diverse for a small, temperate country, with about 150 species; this figure is comparable with the fauna of the British Isles, for example. Tenebrionids are mostly rather large, flightless beetles, although a few species living in rotten wood and in stored products are small. They live mainly in the soil, under logs, or in leaf litter, and feed on dead organic material. 
Members of one New Zealand.genus have the unique habit of feeding on lichens, often on trees at night. Certain species infesting stored foodstuffs are called `flour beetles', and the larvae of others are called `mealworms'. Because mealworms are easily reared in large numbers they are a popular and nutritious form of food for insect-eating animals kept in captivity. Darkling beetles can be recognised by two fairly conspicuous features: the base of the antenna is covered by a shelf-like expansion called a canthus, and the first three plates covering the underside of the abdomen (sternites) are fused together rather than loosely articulated. Colour is mostly black or brown, but some darkling beetles living on whitish beach sands are paler, and a few are shiny metallic.

Most of New Zealand's darkling beetles are endemic; the exceptions are a few species that were accidentally introduced. Also, most of them are nocturnal, with the exception of some species that inhabit sandy beaches. In contrast, many overseas tenebrionids are active during the daytime.
Many tenebrionids produce defensive secretions which make them distasteful to would-be predators. These substances may stain the skin when the live beetles are handled.
Tenebrionids have a sophisticated system for retaining water in the body which enables them to live in drier habitats than most other beetles.
However, many of the New Zealand tenebrionids live in moist habitats. These species are probably useful as indicators of environmental quality, in that their presence signifies that the places where they occur are relatively undisturbed.
The relationships of Tenebrionidae to other families of beetles are still being debated, although the families Archaeocrypticidae and Chalcodryidae which were split off from the Tenebrionidae are closely related. The New Zealand tenebrionid fauna appears to be most closely related to that of Australia, especially in the tribes Adeliini and Helaeini.
Contributor J. Charles Watt