10.
All species included in the
Polysphincta genus-group develop as ectophagous parasitoids of active spiders, killing their hosts prior to pupation. However, little
information regarding natural history and ovipositing behavior of most species are available. In this study we inspected 85
webs of
Araneus omnicolor to evaluate the frequency of parasitism and host size preferences of the wasp
Hymenoepimecis sp. We also described the web characteristics of normal and parasitized spiders and the wasp ovipositing behavior. About
41% of the adult females of
A. omnicolor inspected were parasitized. The highest incidence of parasitism was observed among relatively small females while no egg
or larva was found in large individuals.
Araneus omnicolor builds a strong web composed of an orb and barrier threads, where the spider rests within a curled leaf. The parasitoid larva
builds its cocoon within this refuge, and modified cocoon webs were not observed. The ovipositing behavior of
Hymenoepimecis sp. was very similar to that of
Hymenoepimecis argyraphaga parasitizing
Leucauge argyra, including the position of the sting, the killing of a previously attached larva, and the expelling of the egg from the base
of the ovipositor.
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