Last month in this column, I discussed (arguably) the most commonly encountered family of beetles for our industry, the dermestids. Because of the many different habits, knowing what genus of dermestid you are after can help considerably. What follows is a breakdown of which structure-infesting genus your pest belongs to, and what you can do about it. If there is a microscope or sturdy hand lens around, use the following key to identify your specimen to genus:

Key to Common Adult Dermestidae*:

(1) If the wings are covered with colored or white scales and the beetle is more round than oval in shape when viewed from above, it is Anthrenus sp. If not, the wing covers will have hairs (which may be colorful or not), and the beetle is oval in shape when viewed from above, then go to step 2.

(2) Examine the head to see if the area between the compound eyes is without an ocellus (simple eye) and if the beetle is greater than 7 millimeters. If so, it is Dermestes sp. If not, the head will have a single ocellus (be sure to use magnification!) and the beetle will measure roughly 3-7 millimeters in overall length, then go to step 3.

(3) If the first tarsal segment of the hind leg is compact, and much shorter than the second tarsomere, and the last antennal segment in the male is longer than the rest of the antennal club combined, it is Attagenus sp. If the first tarsomere of the hind leg is as long (or longer) than the second tarsomere, and the last antennal segment of club is never enlarged it is Trogoderma sp.

Now that you know you are dealing with a dermestid and to which genus it belongs, you must decide what to do about it. The factors that will dictate your decision should include:

  • The number of beetles that you (or the client) are finding
  • What genus they belong to/what they are infesting
  • The tolerance of the client (food industry and museums will have little tolerance)

Remember, dermestids are not a well recognized pest to most clients, and therefore generally do not receive the “zero tolerance” approach afforded the treatment of the roaches and bed bugs of the world. There will be times when a single adult dermestid or larva is intercepted on a monitoring device, which need not trigger any remediation. It should, however, make you reassess the layout of your monitors. Are there enough monitors to tell you if there is a problem? Or are most of the devices rodent bait stations or mechanical traps without glue boards? Are the devices appropriately located where these beetles would find food? If low numbers are consistently encountered, a thorough inspection of the area should result.

The genus Trogoderma is the one most likely to trigger a treatment from a PMP. Trogoderma beetles are common in food production and food storage plants and are a much-feared pest as they prefer to feed on plant-based protein like grains, pastas, and spices. This genus includes the infamous Khapra beetle.

Trogoderma love rodenticide baits. This may factor into your selection of pest control devices! They contaminate food with their bodies and long pointed hairs found on the larvae, called hastisetae. For Trogoderma, using a light trap or a wing trap containing an appropriate pheromone is a good way to monitor your treatment’s progress, as most adults are excellent fliers (unlike Khapra beetles). Achieving control from these monitors is unlikely; they mainly target older males and females long after they’re capable of reproduction. If small quantities of food are infested, it may be discarded. If found in a large quantity of food, fumigation may be necessary. Thorough sanitation is key to keeping these populations low.

Beetles in the genus Anthrenus are commonly encountered in homes. Their food preference is usually dead insects or natural fibers (e.g., wool). They used to be a huge problem back when natural fibers were used extensively for insulation, upholstery, floor coverings, and clothes. Nowadays, they probably are the least important of the dermestids to a professional (unless you service a museum!), but can reach massive populations in certain circumstances (e.g., when there are overwintering pest problems).

Attagenus is the group that includes the black carpet beetle. This beetle loves to show up in areas of dead skin accumulation, like bedrooms, and situations where dead insects are found. These beetles are great at finding abandoned hymenoptera nests and chewing on the leftovers — be sure that you are not the one leaving any Attagenus snacks after these treatments! They also fancy the pollen from blooming flowers and can be quite common in areas that have extensive gardens. Crack and crevice, spot, or void treatments with an appropriate insecticide are generally adequate for control in a home environment.

The large skin beetles, in the genus Dermestes, will show up wherever vertebrate protein is available. This group includes the larder beetle. Clients like poultry houses, butchers, rendering plants or pet food outlets can have problems. They are also common in homes or businesses with rodent problems. Always try to minimize the available food during any control effort. If the food source cannot be removed, regular sanitation, in conjunction with targeted insecticide applications, should be encouraged. These beetles have been known to damage wooden structures by boring into them when large numbers of larvae look for areas to pupate. In places of high Dermestes pressure, barriers made of thick plastic or metal have been valuable for restricting the larval movement and protecting wooden structural timber.

All employees should be able to recognize dermestids and realize that there is no “one-size-fits-all” approach. Knowing your client’s concern level regarding these beetles and which beetles are actually present is a great way to determine when action is required.

*Note: This key is simplified but will work for all commonly encountered species.

The author is manager of education and training for Rose Pest Solutions, Troy, Mich.