Lonchaeid Fly

How to identify it

• Adult lance flies (family Lonchaeidae) are shiny black and about 5 to 6 mm long.^[2]
• The larvae are very small maggots covered with minute spines, found under the bark of pine and spruce leaders already infested by the white pine weevil or northern pine weevil.^[2][1]

Where it lives

Well established in North America, its distribution coincides with that of the white pine weevil and the northern pine weevil. It is found mainly in white pine, jack pine, red pine and Norway spruce plantations.^[1]

Biology and life cycle

Lance flies generally live in association with bark-feeding beetles, acting mostly as scavengers or predators of other insects. This species is a major facultative predator of the white pine weevil in the terminal shoots of certain conifers, and often occurs with the northern pine weevil as well.^[1][2]

The young larvae feed on dead or dying weevil larvae, weakened by disease or parasites, and on frass. As they grow they become predators of healthy weevil prepupae and pupae, taking the immobile stages because they have trouble catching active prey. A diet of live prey makes them grow faster, and one larva eats more than three weevil pupae during its development.^[1]

There is one generation a year. The fly overwinters under the bark as a larva, completes development the next spring, and the adults emerge from late May. Females lay their eggs under bark that other insects have already infested.^[1]

It can also eat the larvae of other insects that parasitize the weevil, so its benefit is not entirely one-sided.^[1]

Damage and signs

• This fly does no damage. At high larval densities it is one of the most effective natural enemies of the white pine weevil and can eliminate up to 85 percent of the weevil's larval population; the USDA manual likewise records it as an important enemy of that weevil.^[1][2]

Health risk

Neither source reports any effect on people; the fly lives under bark in weevil-killed leaders.^[1][2]

Control

Prevention

No control is needed; the fly is a beneficial predator. When pruning out weevil-killed leaders, remember that the flies, like the weevils, are developing inside them.^[1]

Related profiles

• White Pine Weevil
• Tachinid Flies
• Longlegged Flies

Common questions

Are the small black flies around the dead leader of my white pine a problem?

If they are lance flies of this kind, no. Their larvae feed on white pine weevil larvae and pupae inside the dead leader, and at high numbers they kill most of the weevil brood.^[1][2]

Does Lonchaea corticis control the white pine weevil on its own?

Not reliably. Natural Resources Canada calls it one of the weevil's most effective natural enemies at high larval densities, and it can remove up to 85 percent of the larvae, but it is a facultative predator that also eats dead larvae and frass.^[1]

Sources

1. Natural Resources Canada, Canadian Forest Service, “Lonchaeid fly (Lonchaea corticis), Trees, insects and diseases of Canada's forests.” tidcf.nrcan.gc.ca/en/insects/factsheet/3937 (accessed 2026-11-10)
2. USDA Forest Service, “Eastern Forest Insects, Miscellaneous Publication 1175 (W. L. Baker, 1972; scanned copy).” archive.org/details/easternforestins1175bake (accessed 2026-11-10)
3. iNaturalist, “Lonchaea taxon page (order and family).” www.inaturalist.org/taxa/371578 (accessed 2026-11-10)