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Heloridae = Link 1
Description & Statistics
Heloridae. -- There is but one North American species, Helorus paradixus (Provancher), a black insect about 4.5 mm long with a more or less complete venation in the front wings. This species is a Parasite of the larvae of chrysopid lacewings. Adults emerge from the host's cocoon.
Helorus paradoxus Prov. was studied by Don Clancy (Clausen 1940). This species is mostly restricted to Chrysopa majescula Banks, though several other species of the genus occur in the same habitat. Females have a preoviposition period of 2-8 days, after which host larvae are attacked in any stage of development. The abdomen is brought forward beneath the body, and the ovipositor is inserted into the lateral or lateroventral region of the host body, usually the abdomen. After insertion, the female folds her legs and may be dragged for a time by the excited host. Only a single egg is laid at each insertion, and adult life may extend to 4-6 weeks. During this time ca. 50 eggs are laid, usually 1-2 per day.
The egg is free floating in the host body fluids, where it increases much in size during incubation. The embryo lies curled within the shell with the head at the micropylar end (Clausen 1940/1962). Hatching occurs in a minimum of 2 days after deposition. Duration of the larval period, in particular the 1st instar, is variable, for the first molt does not occur until the host cocoon is spun and the prepupal stage attained. In hosts that carry over until the second year, the parasitoid persists in the first stage through that extended period. When oviposition is in nearly mature host larvae and under summer conditions, the stage lasts only 3-6 days. Soon after the first molt, the host body fluids become filled with opaque white spherical bodies. As these increase in number there is a corresponding decrease in the fat bodies and softer tissues. It seems that the parasitoid larva has to secrete an enzyme which is necessary for the breakdown of the host tissues. All host movement ceases about the middle of the parasitoid's 2nd larval stadium, and death occurs coincident with the second molt. The 2nd instar lasts 2.5-3 days. Feeding is very extensive after the second molt, and the body contents of the host are completely devoured within 2 days. The parasitoid orients its body in reverse to that of the host. After remaining in the empty skin for several days, the larva emerges from a point near the posterior end, and only the last 4-5 segments remain embedded in the wound. Another resting period follows before pupation takes place. The tip of the pupal abdomen retains a light attachment to the host remains, and the body is greatly curved to fit the outline of the host cocoon. The larval meconium is not voided until after adult emergence. The pupal stage is completed in 8-12 days, giving 22-40 days for the complete cycle from egg laying to emergence (average of 30 days). Several generations are produced yearly, and hibernation is as the 1st instar larva within the host larva in its cocoon.
This is a small family. The hosts seem limited to Chrysopidae, and parasitoids are internal on lacewing larvae, with adult emergence being from the cocoon. The body is only about 6.5 mm. long, stout, and mostly black. The sickle-shaped mandibles are long and cross over in the shape of a scissors. The labrum is long and narrow and usually not exposed. The flagellum has a ringed article between the pedicel and segment 1. The forewing has 5 closed cells including a subtriangular first medial cell. Tarsal claws are pectinate. Metasomal segment 1 is distinctly elongated (petiolate). The etasomal terga 2-4 are fused into a syntergite (Masner 1993).
All species are solitary endoparasitoids in larvae of Chrysopidae (Neuroptera), and the dults emerge from the host cocoon.
For detailed descriptions of immature stages, please see Clausen (1940/62).
Kozlov, M. A. 1978/1987. Family Heloridae (Helorids). In: G. S. Medvedev (ed.) 1987, Keys to the Insects of the European Part of the USSR. Vol. 3 Hymenoptera, Pt. 2. Akad. Nauk., Zool. Inst., Leningrad, SSSR. (trans. fr. Russian, Amerind. Publ. Co., Pvt. Ltd., New Delhi). 1341 p.