Description & Statistics
Martelli (1908) studied an undetermined species which was predatory on the eggs of Filippia oleae Costa in Italy. During oviposition the female fly stands either on the egg sac or at one side of it, inserts the ovipositor beneath the margin or through the wax covering, and lays an egg among those of the host. The entire contents of the sac are consumed by one larva,a nd the cycle from egg to adult takes 30 days. There are 4-5 generations annually.
Cottam (1922) studying some unnamed species that are common predators on aphids in Africa. One was effective in controlling Aphis sorghi Theo. Cherian (1933) studied the life history of Leucopis sp., an aphid predator in India. The egg is 0.36 mm long, white and ribbed longitudinally. First instar larvae lack the integumentary hairs, but the mature form has several fleshy processes on each body segment. The posterior spiracles of all instars are borne on stalked processes, which are most pronounced on the mature larva and the puparium. Before pupation the larva exudes a great quantity of mucilaginous substance, which darkens quickly and attaches the puparium to the substratum. The egg, larval and pupal stages require 2-4, 4-5 and 5-7 days, respectively.
Clausen (1940) referred to an unpublished M.S. Thesis by Maple treating of Leucopis bella Lw. and L. griseola Fall in North America. L. bella is a common predator of eggs, and possible young larvae, of dactylopine Coccidae, while L. griseola is an effective natural enemy of aphids. Eggs of both species are ca. 0.5 X 0.16 mm., with the anterior end a bit pointed, and are pearly white, with the surface bearing longitudinal ridges. They are laid singly among the egg masses or colonies of the host, where they hatch in 3-4 days.
Leucopis bella has three larval instars. The first is white, later becoming reddish, broadest in the abdominal region, and bluntly rounded posteriorly. It tapers markedly toward the head. The integument is bare. The posterior spiracles are simple and borne on prominent conical extensions. The anterior spiracles are minute. Third instar larvae are 5.00 mm long and clothed only with tiny setae. The posterior spiracles are borne on long cylindrical processes, which are widely separated, diverging and directed dorsad. Each spiracle consists of three curved, fingerlike projections, each of which bears an opening at the apex. The larva of L. griseola differs from that of L. bella by having small, fleshy spines on all body segments. In both species, the number of molts varies, apparently with temperature. Some individuals have only two larval instars rather than the usual three.
Pupation occurs among the egg masses of the host. An incomplete cocoon is spun, composed of a network of coarse threads, which may serve as a means of attachment. It is not formed when pupation occurs in the open. The puparium is dull reddish brown, and indistinctly segmented except for the anterior portion. Stalked caudal spiracles of the mature larva persist unchanged, and there are no protruding prothoracic pupal cornicles (Clausen 1940/62).
There are several generations annually, and in summer the egg, larval and pupal stages are completed in 3-4, 8-12, and 13-14 days, respectively. Winter is passed in the pupal stage in temperate regions.
Malloch (1921) noted puparia of several predaceous species from Illinois. The puparium of L. orbitalis Malloch has minute, 4-branched anterior spiracles,and the caudal pair are borne upon short, stout stalks lying closely to the substratum on which the puparium is formed. The posterior spiracles of Leucopomyia pulvinariae Malloch are very small and sessile, differing in this respect from those described for other species of Chamaemyiidae. All species were found to have the ventral side of the puparium somewhat flattened and sometimes the dorsum depressed.
This family had about 205 known species as of 2000. Although cosmopolitan, they are mostly Holarctic. Diagnostic characters include a complete costa and anal wing vein; postvertical bristles; interfrontal bristles that are absent and a small clypeus. The body is smaller than 4 mm, grey with black dots on the abdomen. The arista is hairy or bare, the front femur contains bristles and the preapical tibial bristles are absent.
Immature Chmaemyiidae are predators of scale insects, mealybugs and aphids. They are of some importance to biological pest control, and some have been transported to North America for balsam wooly aphid control..
Some species are hyperparasitoids of Hemiptera. The African genera Alloxysta and Phaenoglyphis are hyperparasitoids of Aphididae via Aphidiinae (Hymenoptera: Braconidae) and Aphelinidae (Hymenoptera: Chalcidoidea). Species of the African geners Apocharips and Dilyta are hyperparasitoids of Psyllidae via Encyrtidae (Hymenoptera: Chalcidoidea).
Cole, F. R. 1969. The Flies of Western North America. Univ. Calif. Press, Berkeley & Los Angeles. 693 p.
McAlpine, J. F. 1960. Canad. Ent. 92: 51-8.
McAlpine, J. F. 1963. Canad. Ent. 95: 239-53.