Know Your Friends

Damsel Bugs

Damsel bugs (or nabids, from the family name Nabidae) are slender, tan-colored bugs that resemble small, smooth-looking assassin bugs or other plant bugs that feed on crops. This small family of generalist predators is commonly found in many crop and garden situations. Some other species of damsel bugs are black, but these are less common in agriculture. Damsel bugs feed on many types of insects. They are predators of aphids, moth eggs, and small caterpillars, including corn earworm, European corn borer, imported cabbageworm and some armyworms. Other prey may include leafhoppers (including beet and potato leafhoppers), small sawfly larvae, mites, tarnished plant bug nymphs, and asparagus beetle and Colorado potato beetle eggs and nymphs. A European tree-inhabiting species, Himacerus apterus, has been reported feeding on red spider mites in English orchards, on gypsy moth in the Ukraine, and on spanworms in Poland. Although they can survive for up to two weeks without food, if no other prey is available they will turn to cannibalism.

Damsel bugs are attacked by a number of natural enemies themselves, including tachinid flies, wasps and fungi. The parasitic tachinid Leucostoma simplex was found in 44% of adult Nabis americoferus and 24% of the nymphs, but in lesser amounts in other Nabis species. Several egg parasites have been recorded, with the mymarid wasp Polynema boreum parasitizing up to 70% of the eggs in California alfalfa fields. Damsel bugs are also susceptible to the entomopathogenic fungus Verticillium lecanii.

Members of the genus Nabis are the most abundant damsel bugs in crops. Three species are common in the Midwest, but their distribution varies somewhat: N. americoferus has the broadest distribution, from southern Canada through the northern half of the United States; N. roseipennis occurs primarily in the northern and eastern parts of the North Central region; N. alternatus is more of a western species, not often found east of the Mississippi River. These are all similar in appearance. Some have only one generation per year; others have two to five generations, depending on location. Most species of damsel bugs overwinter as adults.

Damsel bugs are more commonly found in field crops such as alfalfa and soybean than in row crops or orchards. Grassy fields tend to have more damsel bugs than do broadleaf weed or weed-free fields. They are also commonly found in home gardens, where they prefer to take shelter in low growing grasses and ground covers. Maintaining such environments will encourage these predators, although the impact of damsel bugs in vegetable crops is not known.

Damsel bugs can provide some natural control of pest species, but they are not commercially available for augmentation.

- Susan Mahr, University of Wisconsin - Madison

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