roseslug

not listed

not listed

not listed

Roseslug is a very small common sawfly. It is native to northern Europe. It was introduced into North America, and now occurs from coast to coast in northern United States and southern Canada. It is uncommon in Minnesota.

Adults are wasp-like and ⅛″ to 3 ⁄16″ (4 to 5 mm) long. The head, thorax, and abdomen are black. The abdomen is broadly joined to the thorax. The antennae are black, thread-like, and have nine segments. The wings are uniformly tinged dark smoky brown. The forewing does not have a vein crossing the cell on the leading margin (intercostal vein). The hindwing has three basal cells. The legs are mostly black. The second leg part (trochanter) has two segments. On the front and middle legs, the tip of the third leg segment (femur) and all of the fourth segment (tibia) are yellowish-white.

The larvae is looks like a caterpillar but is not. The term “caterpillar” refers only to larvae of moths and butterflies. The roseslug larva is up to ⅝″ (15 mm) long. The head is yellowish-brown. The body is translucent yellow. It often appears tinged green in the middle due to the contents of its gut. There are three pairs of true legs on the thorax and six pairs of fleshy, unsegmented, leg-like structures (prolegs) on the abdomen.

Total length: ⅛″ to 3 ⁄16″ (4 to 5 mm)

One generation per year: May through late June

Larvae feed on leaves of rose plants. They eat only the epidermis and spongy layers of tissue on the underside of the leaf between the veins. The tissue that remains turns brown. The resulting damage is called windowpane skeletonization.

Adults emerge in May. The female cuts into a leaf edge with her saw-like ovipositor and deposits her eggs. The eggs develop into embryos without first being fertilized by sperm (parthenogenesis). In late June the larvae drop to the ground and pupate. Pupa overwinter.

Leaves of rose (Rosa spp.)

Sources

24, 29, 30.

Widespread but not common

Location: Woodbury, MN