Parasitization of a libellulid dragonfly, Urothemis assignata Selys (Anisoptera: Libellulidae) by water mite larvae of the genus Hydrachna (Acarina:
Hydrachnidae
)

HASSAN, A. T

ABSTRACT:

The parasitization of a libellulid dragonfly, Urothemis assignata Selys, by mite larvae of the genus Hydrachna is reported here for the first time. Infestation was initiated usually on the ultimate instar in water, although occasionally, the penultimate ins tar was infested. Parasitization of the adult host was evidenced by the presence of mites or their scar on the wings. Adults and larvae were parasitized all the year round, most heavily during the dry season (October to May). The number of the mite larvae per host varied between
12 and 206, while parasitism in the sample population ranged between 55 and 900/0. The transfer of mite larvae from the host larvae to adults during ecdysis seemed to coincide with the period of wing withdrawal from the cast skin. Mites re-entered water during
territorial defence and mating of their adult hosts. There is evidence that the mite larvae develop into nyrnphochrysalis or nymphs before dropping into water. Out of the other 10 common libellulids screened for mite parasitization, only three had mites. Hygrobates sp. was recorded on two of the three, whilst the third had Hydrachna sp.

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