Bad Bugs: Case Study – Ant Bees/Flat Wasps

Bad Bugs: Case Study – Ant Bees/Flat Wasps

By Alain VanRyckeghem, BCE
Technical Director

Recently, reports of biting/stinging insects have occurred in food plants. One concern obviously would be bedbugs, but in these cases there were no bedbugs to be found in the plant or lockers. The stings would occur on the neck, cuffs and hands of employees while actively working. This is not typical of bedbug biting. Some of the welts were quarter sized.

After collecting samples from clothing with a lint roller and further inspection of the material recovered, there were several tiny insects caught on the tapes. At first they appeared like ants; in fact they resemble pharaoh ants which were light yellow
and about 1-2 mm long with elbowed antennae. The giveaway that these were not ants was the lack of a node between the thorax and abdomen. The insect was identified as Cephalonomia gallicola, which belongs to the aculeate wasp family Bethylidae.

This tiny 1-2 mm wasp has a wingless female and a male that can have wings or not. Identification to species can be confirmed by the overall light yellow color, flattened head, squared off posterior corners of the thorax, and terminal 6 segments of the antennae darker than the basal six. The male wasps can fly, while the female does not. Both will sting. This most often occurs when the insect is caught up against the skin and clothing. The females can crawl readily like ants
and so may move onto clothing or fall off surfaces onto people while handling product. The key element to understanding and managing this insect was to determine the origin of the wasps.

This wasp is a parasite of the larval stages of cigarette beetles, drugstore beetles and some spider beetles. Other relatives in the Bethylidae family are also parasites of Anobiid beetle larvae like the furniture beetles, Anobium punctatum. Those wasps, Sclerodermus domesticus, also can deliver stings and severe reactions.

These wasps have been recorded in the eastern US, Europe, and Asia, and are likely cosmopolitan. Adults emerge from parasitized larvae from February through October with the majority appearing from July through September. Spring emergence requires 60 days from egg to adult while summer only requires 20-30 days. Adult females can overwinter for a
period of 60-180 days, but males die about 10 days after emergence and mating. Females will not lay eggs below 60 °F (15.5°C) or above 104°F (40°C). This wasp will continue to survive indoors year round if larvae of the cigarette beetle (Lasioderma) and drugstore beetle (Stegobium) are readily available. Spilled product of only 2 mm thick on ledges can support larval development in cigarette beetle. Small pockets of spillage or accumulations in cracks and crevices also provide suitable habitat. For more information, contact insecthelp@aol.com.

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