The association between larval parasitic water mites (Hydracarina) and Anopheles implexus (Theobald) (Diptera, Culicidae)

Abstract

The parasitic larvae of two species of water mites were studied on resting and biting Anopheles implexus (Theo.) from the Zika Forest near Entebbe, Uganda. Details are given of the mites' morphology, positions of attachment, growth stages and visible effects on hosts. Living larvae of the more numerous mite species (designated as species F, Limnesiidae) were only moderately reliable indicators of the nulliparous state of female hosts, whereas those of the other species (species G, Arrenuridae) were more reliable nullipar indicators, evidently owing to their far more rapid development. The presence of living larvae of either species not completely full-grown denoted the nulliparous state of female hosts with certainty. Male mosquitoes showed consistently lower infestation rates than females from the same resting samples, but the incidence of the different growth classes of species F indicated that these mites departed from hosts of either sex with equal facility and therefore regardless of whether the hosts returned to oviposition sites or not. Frequency distributions of species F on each host sex fitted most closely to highly clumped negative binomials, and biological interpretation of patterns of decline in mite numbers on females in successive Sella's stage groups, and other data, provided evidence of there being at most a negligible amount of mite-mediated host mortality.The study confirms the usefulness as well as the limitations of the presence of parasitic water mites as a rapid means of age-grading female mosquitoes, and suggests several new applications.

The behavioural ecology of host selection in Anopheles implexus (Theobald) (Diptera, Culicidae)

“…Differences between the activity patterns of females at nectar and blood sources, most evident in the first two hours of the night, do not necessarily imply that nectar response thresholds are modulated by separate endogenous control, for not all the unfed females would have been ready to bite, and the more recently emerged females may well have had a distinct activity pattern. In this respect a study of the temporal incidence of different growth classes of mites (McCrae, 1976) comparing nectar-feeding with blood-feeding mosquitoes could be instructive.…”

“…It involved distinguishing between nulliparous and parous females, using as criteria the presence or absence of ovarian tracheolar ' skeins' and relict ova (Detinova, 1962), with handling techniques as described by Davies et al (1971) and McCrae (1972). The attachment of living larval water mites was found to provide a useful if imperfect criterion of nulliparity (McCrae, 1976), and this paper also presents evidence for the absence of a 'pre-gravid' stage (Gillies, 19546, 1955) in female A. implexus, which would otherwise have added considerable complications to interpretation.…”

“…To the numbers of age-graded females reported by McCrae (1976) may now be added the results of previous dissections. These two sets of data are given in Table XII and indicate that the parous rate or mean age of cattle-biting A. implexus outside forest is higher than of those taken in any kind of catch inside the forest.…”

Review of Parasitic Associations of Larval Water Mites (Acari: Parasitengona: Hydrachnida) With Insect Hosts

“…Larvae that appear to be limnesiids have been reported from mosquitoes in the tropics (Speer 1927;Laird 1947;McCrae 1976;.…”