|Macremphytus tarsatus |
common name Dogwood Sawfly
Deciduous, mixed wood forests; urban ornamentals, various species of dogwood (Cornus).
Adults emerge from cocoon in late May to July. Larvae present July through October (Philip and Mengersen 1988: 58).
Adults: Adults are brightly colored wasp-like insects (four membranous wings with hind wing smaller than forewings, venation apparent, ovipositor well developed, legs have 5 segments (Triplehorn and Johnson 2005: 481)). Pits of episternum and scutellum are scattered and small or absent. Anterior (front) margin of clypeus, a hardened plate on lower part of face, is widely concave. The pedicel, or second section of the antennae away from the head, is as wide as or wider than it is long. The antennae are bi- or tri-colored. The episternum of mesothorax (middle or second section of the thorax) is clearly pitted. The length of first leg section (metatarsomere) of the leg attached to the third section of the thorax is at least 1 times that of combined sections 2-5. Cell M of the hind wing is closed (Goulet 1992: 164-166).
Larvae: Dogwood larvae have black heads. Their bodies are also black, with yellow bars across the back. The underside of the larva is solid yellow. The head and body is covered in white floculence (a powdery substance) except during last instar and immediately following each molt. They are about 22mm long at maturity (Ives and Wong 1988: 193).
The dogwood sawfly is found on ornamental and native dogwoods. Adults are rarely seen, but emerge from the pupal overwintering site in the spring to lay eggs on the underside of dogwood leaves. Over 100 eggs may be deposited on the underside of a single leaf (Philip and Mengersen 1989: 58). Upon hatching, the larvae feed on the leaf, leaving it skeletonized. They eat all but the midvein (Johnson and Lyon 1991: 126). After molting for a second time, the larvae become covered with a powdery material that mimics the appearance of bird droppings, and which can be easily rubbed off. This is thought to aid survival (Johnson and Lyon 1991: 126; Philip and Mengersen 1989: 58). The spotted coloration of the final instar is also believed to provide camouflage as the larvae crawls about the ground in search of an overwintering site. Once found, the larvae pass the winter in a prepupal state in cocoons made of rotted wood. If rooted wood on the ground cannot be found, they will seek wood fiberboard and siding used in houses. Woodpeckers are proficient at detecting their presence. Pupation occurs in the spring, with only one generation per year (Johnson and Lyon 1991: 126; Philip and Mengersen 1989: 58).
Dogwood sawflies are an occasional pest on the prairies (Philip and Mengersen 1989: 58) and do not present any economic concerns as they do not damage or kill their hosts.
Larvae are external feeders on the leaves of dogwood (Cornus).
Canadian prairies, northeast U.S. and the Great Lakes states.
|species page author||Marshall, H.||2005 |