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Parasitic mites (Acari Hydrachnidia) on Pupae
and Adults of Simuliidae (Insecta Diptera)
Alfons Renz1), Reinhard Gerecke2), Peter
Martin3) 1) Alfons.Renz_at_uni-tuebingen.de 2)
Reinhard.Gerecke_at_uni-tuebingen.de 3)
PMartin_at_zoologie.uni-kiel.de
Abstract Larvae of various species of water
mites (Hydrachnidia) are known to parasite on
adult blackflies. Typically, the larvae of these
mites are located inside the pupal cocoons of
Simuliidae, where they wait until the imago
hatches. They then attach to the emerging adult
fly, engorge by feeding on the hosts haemolymph,
and profit from its upstream movement to
compensate for downstream drift and thus
repopulate seasonally fast-flowing breeding
sites.
Sperchon larva on Simulium pupa
Observations In 2003 and again in 2004, we
observed extraordinarily high prevalences of
Sperchon cf. setiger in some streams around
Tübingen in Southern Germany. In the parasitized
populations of Simulium equinum, S. ornatum and
S. latipes, prevalence rates were high, reaching
80 to 90 in over 100 pupae examined, and the
average number of larvae was 3-5 mites per
Simulium pupa, with a typical negative-binomial
distribution pattern. Mites were seen crawling
avidly over and into the pupae cocoons, but were
not attracted by Simulium larvae, even when these
were situated close to the pupae. Only one mite
was seen on a female adult fly, hatched in an
emerging cage. A distinctive melanization marked
the site, where the mite had previously fed.
Mite larvae of different sizes were seen on the
pupae, indicating that some mites were actually
feeding and might therefore develop to nymphal or
even adult stages, without passing through a
phoretic stage on the emerging adult fly.
Mite
Mite
Lesion
Sperchon mite on adult Simlium female
Conclusions Though Sperchon mites are generally
considered being mainly phoretic parasites, their
number and the fact, that they may also suck
haemolymph, makes them potential regulators of
Simulium population. Levels of infestation seem
be linked to water pollution and were lowest in
rivers with little organic load. Like mermithid
nematodes, phoretic mites take advantage of the
upstream compensatory flight of Simulium adult
female flies.
Sperchon spec. larva
Compensation of downstream drift by phoretic
parasites of Simulium adult flies Mites
Mermithids