Hemisarcoptes coccophagus Meyer
Taxonomic placing: Acari, Astigmata, Hemisarcoptidae.
Common name: None.
Geographical distribution: This species, originally found in South Africa, is widely distributed around the Mediterranean. It has been introduced into and had become established in New Zealand.
Economic importance: Hemisarcoptes coccophagus is an important natural enemy of armored scale insects (Diaspididae), especially when no other effective enemies are present.
Morphology: The female is about 0.3 mm long, milky-white in color (which may depend on the color of the host scales), with an irregular propodorsal shield. All body setae and short and simple. The genital and anal apertures are confluent, flanked by four setae, of which one is as long as the body. The tarsi bear sucker-like empodia. The hypopus is dark brown with a pair of eyes. It has an anal, ventral sucker plate and each of its two anterior legs bear a single foliate seta on their tarsi; the posterior leg terminates in two long and strong setae.
Biology: At 28°C the mite requires about two weeks to raise a generation when feeding on an optimal host [e.g. latania scale, Hemiberlesia lataniae. Fecundity is host dependent: a female produces 80-90 eggs on latania scale, but only very few on unsuitable hosts, like oleander scale, Aspidiotus nerii. A young host female may support two mite generations, but the eggs, juveniles and male scale pupae are rapidly killed by the mite. The plants on which the scales live affect their size, and thus the fecundity of the feeding mite. The sex ratio of H. coccophagus is variable during the year as well as on its different hosts, strongly male-biased on latania scale during fall and winter, becoming female-biased in late spring; on oleander scale it was distinctly male-biased, whereas on chaff scale, Parlatoria pergandii the sex ratio fluctuated. In the Middle East the mite is dispersed during its hypopal stage by the coccinellid Chilocorus bipustulatus. The main impact of H. coccophagus on chaff scale infesting citrus in Israel is during summer, when the pest’s populations ebb whereas the mite numbers peak.
References
Gerson, U. and Izraylevich, S. 1997. A review of host utilization by Hemisarcoptes (Acari: Hemisarcoptidae) parasitic on scale insects. Systematic and Applied Acarology 2: 33-42.
Izraylevich, S. and Gerson, U. 1993. Population dynamics of Hemisarcoptes coccophagus Meyer (Astigmata: Hemisarcoptidae) attacking three species of armored scale insects (Homoptera: Diaspididae). Experimental and Applied Acarology 17: 877-88.
Izraylevich, S. and Gerson, U. 1995. The hypopus of Hemisarcoptes coccophagus Meyer: distribution and apolysis. Acarologia 36: 333-339.
Izraylevich, S. and Gerson, U. 1996. Sex allocation by a mite parasitic on insects: local mate competition, host quality and operational sex ratio. Oecologia 108: 676-82.
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