Southwestern Squash Vine Borer

Common Name: Squash vine borer
Scientific Name: Melittia calabaza
Order: Lepidoptera

Description: The day flying adults are primarily orange and black superficially resembling a wasp. The forewings are covered with metallic olive-brown scales. The hind wings are mostly clear with a brown edge. The abdomen is bright red and ringed with black bands. Adults have a wing spread of about 1 – 1.5 inches. The larvae are white with a brown head. They do not appear to have prolegs and are about 1 inch long.

There are at least two species in Texas; the southwestern squash vine borer, Melittia calabaza Duckworth & Eichlin and the squash vine borer, M. cucurbitae (Harris).

Life Cycle: Adult females lay eggs on leaves and stems of squash. Larvae hatch from eggs and soon burrow into host plant stems. The caterpillars develop through several stages (instars). When full-grown the larvae climb from the stems and pupate a few inches deep in the soil. Adults may feed on nectar. Adults may sit on the leaves of squash early in the morning. Larvae can be dissected from infested vines. Pupae form in earthen cells in the soil which may be found when the garden is tilled. There are probably two broods in Texas.

Habitat and Food Source(s): Caterpillars have chewing mouthparts. Adults have siphoning mouths. They feed almost exclusively in squash and closely related wild plants. They may attack a few related plants like melons and cucumbers on occasion.

Pest Status: One of the most damaging and most common pests of squash, especially in home gardens; medically harmless. Larvae are borers and tunnel inside the stems, causing considerable damage to squash. Excrement (frass) may extrude from the stems and stems may wilt and die.

For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.

Literature: Metcalf, Flint and Metcalf. 1962. Swan and Papp 1978.