The flour beetles belong to the Family Tenebrionidae which also contains the larger mealworm beetles and the darkling beetles. Tenebrionids can be distinguished from similar looking beetles by examining the tarsi on the legs. On these beetles, the front and middle legs have five-segmented tarsi while the tarsi of the hind legs has only four segments.
The two most common flour beetles are the red and confused flour beetle, Tribolium castaneum and T. confusum, respectively. These two beetles range up to 3/16 inch (5 mm) and are reddish brown in color. The two beetles are nearly identical and are most easily distinguished by examining the antennae. The antennae of the red flour beetles end abruptly in a three-segmented club while tip ending in a four-segmented club. Additionally, the sides of red flour beetle’s thorax are curved while the confused flour beetle’s thorax has straighter sides.
Any facilities that processes meat or cheese products is subject to infestations of the red legged ham beetle. This beetle does not attack grains as do other stored product beetles, rather it breeds in dried or smoked meats and cheeses. Its nickname is the copra beetle because it is a serious pest of this product which is made of dried coconut meat. Other items attacked include bacon, stored fish, fish meal, bone meal, animal mounts, dog biscuits, museum artifacts, garlic. The red legged ham beetle even has been used by museums and zoos to strip the meat off animal skeletons, and it can be found in slaughter houses and rendering plants where livestock animals are killed for processing as food. It has also been found infesting pet food processing facilities.
Biology & Life Cycle
Red legged ham beetle females lay from 400 to 2000 translucent eggs that are 1 mm in length onto exposed meat, cheese or a similar substrate. The elongate, purplish larvae bore into the food source and undergo several molts before growing their full size of 3/8 inch (10 mm). The fully grown larvae migrate out of the food source to find a dry site to pupate and can be found in cracks and between the folds of packaging. The life cycle can be completed in as little as 30 days – 17 days as a larva and 13 days in pupation. Adults are rather long-lived, surviving up to one year or longer, and several generations can be produced each year.
Both the larva and adult red legged ham beetles feed on and damage ,eat, but the larvae are responsible for most of the damage. Adults and larvae are also predaceous and voraciously attack cheese skipper, Piophila casei, which is commonly found infesting the same types of food products. Blow fly larvae are also attacked and eaten, and when large populations of this beetle develop, cannibalism helps keep the numbers down. Larvae and adults both avoid light and prefer to hide within the food product or under folds and flaps of packaging. This beetle also can be found in bales of cotton, rattan, woolen goods and salt, although it does not feed on or breed in these items. When disturbed, the adults may also emit a strong odor which is likely a repellent to protect it from predators.
Adult beetles are capable of slow flight but prefer to crawl and can move quickly. When large populations are allowed to develop in stored meats, cheeses, etc., adult beetles may migrate to adjacent areas or buildings by crawling or flying.
Two other species of Necrobia may be encountered but are seldom pests in buildings: the red shouldered ham beetle, N. ruficollis, and N. violacea. Both beetles feed primarily on the skin and bones of dead animals and on dead fish. The larvae of N.violacea may be beneficial as they feed on the larvae of hide beetles.
When the red legged ham beetle is found within a building, the breeding source will be some sort of meat or cheese product or possibly dog biscuits, stored copra or even a dead rodent within a wall. Inspect all places where meat or meat by-products are stored at room temperatures.
In warehouses, alert for cases of canned or jarred meats that have been damaged, and also for stored copra or cheeses. Often these cases can be located among stacked pallets by detecting the odor of decaying meats and then unstacking pallets in those areas to find the broken cases. Also check the repacking area for damaged meat products and be sure to look for pupal cases in flaps of boxes and in corrugated cardboard. In meat and cheese processing facilities and rendering plants, be sure to inspect for adults in cracks of walls and floors and in shelving in and near where infested products have been found.
One of the best ways to protect meat products from red legged ham beetles is through preventive inspection if incoming meat products, their by-products and meat-based dried meal. Once this beetle has infested meat products, it is too late, and the meat is generally considered unfit for consumption or sale. Regular inspections of processing areas and repacking areas to detect new infestations before they grow large is also a good strategy.
Obviously, meat, cheeses and other products held in cold storage are protected from attack. Regular rotation of these types of products that do get stored at room temperature limits their susceptibility to attack. If infested products are found, these will generally need to be discarded along with all cardboard packaging. Pallets used to store infested products will need to be cleaned thoroughly and treated as necessary if beetles or pupae are found in cracks.