|scientific name Caliroa cerasi Linnaeus|
common name Pear slug (official), Cherry slug, Cherry sawfly
Unknown for adults, larva found on ornamental and horticulture species of the Rosaceae.
In Canada adults emerge and fly in mid-June to late July, elsewhere as early as mid-May.
Adults: Black sawflies approx. 5.0 mm long. Front and middle tibia brownish. Antenna segment 3 shorter in length than segment 4 + 5. All sawflies of this group posses an ovipositor modified to be used as a saw to facilitate the deposition of eggs under the surface of leaves. Lancet (saw portion of ovipositor) with 17 serrulae (teeth), each long and pointed at apex.
Larvae: Small, black and slug-like in appearance, approx. 1.0 mm long at hatch, 11.0 mm long at pupation. Feed on the upper and lower surfaces of leaves. 6 or 7 instars. Dark brown or black head capsule in later instars. Covered with black slime.
Pupae: Forms underground within a cocoon constructed of silk and soil.
Adapted from descriptions in Smith 1971 and Goulet 1992.
Caliroa cerasi overwinters as a pupae, upon emergence females fly to hosts and deposit eggs under the leaf surface. Using the sawlike ovipositor females insert eggs into the leaf from below near the mid-rib or a main vein. After hatching larvae feed on the upper and lower surface of leaves. Larvae are external feeders and skeletonize the host, leaving the vascular structures of leaves intact during feeding. Larval development takes approximately three weeks after which the final instar larvae drop to the ground where they overwinter in the soil. In Canada only one generation per year is produced but in other areas two generations may occur, the second generation emerging a few weeks after the first has finished feeding. Adults can be distinguished from other members of the genus by black slime encapsulating the later larval instars and the all-black legs, other species of Caliroa have some white on the legs. The species is parthenogenic in North America, males are rare in Europe. Caliroa cerasi is likely European in origin and introduced to Canada and elsewhere by commerce. In horticulture stock damage caused to trees by larval feeding can reduce fruit yield and even kill young trees. In ornamental stock damage is considered aesthetically displeasing.
Not of concern, a pest of ornamental and horticulture stock throughout its range.
Larvae are cosmopolitan feeders on hosts in the Rosaceae; especially Pyrus (Pear) and Prunus (Cherry); also Cotoneaster, Crataegus (Hawthorn), Chaenomeles and Cydonia, may also feed on Sorbus (Mountain Ash). In North America also recorded from the Aceracea on Acer (Maple) and the Rhamnaceae on Ceanothus.
European native, introduced to; North America, Eurasia, Africa, Argentina, Chile, Uraguay, Australia, Tasmania, New Zealand, China.
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