How well do you know your beetles? Read about the dermestid family of beetles and tips for larva identification.
The larvae of carpet beetles are called ‘woolly bears’, due to their distinctive, hairy appearance. However, carpet beetles belong to the dermestid family of beetles, which contains some 14 genera and 132 species, the larvae of which all look superficially similar. The bottom line is that when you see a ‘woolly bear’ (pictured above, left) it may not necessarily be a carpet beetle larva. Here is some information on the key dermestid beetles found in residential and commercial situations.
Dermestid beetles have a wide range of common names, including carpet beetle, hide beetle, skin beetle, leather beetle, fur beetle, khapra beetle, museum beetle, larder beetle and warehouse beetle. As many of these names indicate, they often target animal materials, but also, it’s important to note the last two common names – larder beetle and warehouse beetle. Dermestids will eat a wide range of foods – plant material as well as animal material – so some species are considered a stored product pest rather than a fabric pest.
In their natural environment, most dermestids are scavengers of animal material and are found on animal carcasses and in spider webs, mammal, bird, bee and wasp nests. Their larvae have the ability to digest animal material that other animals find difficult to digest, such as hair, fur and skin, as they are one of the few animals that produce enzymes to digest keratin, the protein found in animal hair. However, some species, particularly Trogoderma species such as the warehouse beetle, will also eat a range of dried plant foods, including cereals, seeds and flour.
There are six sub-families of dermestids:
Attageniae: This sub-family includes Attagenus unicolor, the black carpet beetle. Although known for their larvae eating a wide range of animal fibres, they will also eat various dried plant food. The adults feed on pollen.
Dermestidae: The largest of the dermestids, they generally feed on dead animals so can be a pest in buildings when dead rats, birds or animals are left in roof voids or subfloors. Dermestes maculatus, the hide beetle, can be used to help forensic scientists calculate the time of death, as their arrival at a dead body and rate of development follow a predictable time sequence (with a known variation by temperature).
Megatominae: This sub-family contains the largest number of species, including the Australian carpet beetle, Anthrenocerus australis, and the variegated carpet beetle, Anthrenus verbasci. Anthrenus species are also often called museum beetles due to the damage they cause to stuffed animals and insect collections in museums. This group also contains the Trogoderma species, which includes Trogoderma variabile, the warehouse beetle, which is an invasive pest in Australia and one of the major stored product pests globally. It also includes the khapra beetle, Trogoderma granarium, which is similarly considered one of the worst stored product pests. Although occasional incursions have been detected in Australia, it is not currently established.
The other three sub-families, Orphilinae, Thorictinae and Trinodinae, do not have species recognised as significant pests in Australia.
Identifying the species from the larvae is really a job for the experts. Identifying the food source can help narrow down the species, but with a wide range of foods eaten by individual species, and a large overlap of food preferences between species, using the adults for identification is the best option. However, even then, there can be challenges. For each species there will be a size range – adult size will depend on the size of the final instar larvae and that can vary significantly. There can also be great variation in colour and patterns, so there really isn’t an easy way to quickly identify the species – it takes a bit of time and experience.
However, from a treatment point of view, as with any fabric or stored product pest, the first and most important step is the inspection to identify all sources of infestation. Disposing of the infested material can then be followed by the appropriate treatment (if required), which would typically involve an insecticide spray around infested areas. For commercial accounts, monitoring devices should be considered.