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<pyrgotid.htm> [For educational
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DIPTERA, Pyrgotidae -- <Images>
& <Juveniles> These flies are of medium to large size, with long often partly
clouded wings. They are solitary or
gregarious internal parasitoids of adult scarab beetles. Davis (1919) studied Pyrgota undata Wied., a
nocturnal species attacking nocturnal hosts, Phyllophaga spp. To
oviposit, the female alights on the dorsum of a feeding beetle, causing the
latter to fly. At this time she
inserts the ovipositor through the thin exposed integument of the abdominal
dorsum. Female beetles are more often
attacked than males, and the host dies 10-14 days after parasitoid
oviposition. The puparium is formed
within the dead host. There is a
single generation per year, and winter is passed as pupae. In India, Adapsilia flaviseta Ald. commonly parasitizes
beetles of the genus Popillia
(Clausen et al. 1933). Adults are
dirunal as are the ost. Oviposition
behavior is similar to Pyrgota undata, but male beetles are preferred
(ca. 88%) early in the season. Later
only 60% of males are parasitized as their abundance diminishes. Eggs hatch 3 days after oviposition, and
the larval period is 12-15 days. The
beetle is killed by the parasitoid larva soon after its second molt, which is
12-14 days after oviposition. There
is a single generation per year, and hibernation occurs in the puparium
within the bodies of dead host beetles in soil. Clausen (1940) referred to unpublished reports of R. W. Burrell
containing information of the habits of Maenomenus
ensifer Bezzi, as a parasitoid of
adult beetles of Anoplognathus olivieri Dalm. in Australia. The oviposition bvehavior differs from the
above examples in that attack occurs while the host rests on foliage, the
ovipositor being broght forward between the legs and inserted through the
intersegmental membranes, or through the anal opening. There are generally 10-20 parasitoids able
to mature in each host, but a maximum of 33 was obtained. Pupation occurs externally between the
elytra and abdomen of the dead host in soil. It was concluded by Clausen (1940) that on the basis of information
available on behavior of Adapsilia
and Pyrgota, that these and other
species of similar habit can be of very little value in the natural control
of scarab pests. The long larval
period makes it probable that a portion of the oviposition potential of female
scarabs is realized before death. The
pronounced preferences of Adapsilia
for male hosts reduces its value, because the portion of its effective
reproductive capacity expended on the male sex is wasted. Death of male beetles contributes nothing
to population reduction of the following generation, even though it
perpetuates the parasitoid (Clausen 1940/62). For detailed descriptions of immature stages of Pyrgotidae,
please see (Clausen 1940/62). References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] |