Appearance
At around 3.4mm average for females and 2.9mm for males these Torymid wasps are fairly large for Chalcids. With their yellow body and some darker markings the species of the the genus Megastigmus are quite recognizable on first sight and only a few species develop on Rocacaea (most others on Conifers). Only recently a handful of additional species from Angiosperms has been described from Africa.Of the species occurring in the Palearctic region, M. aculeatus has the longest ovipostor. Other characters include the shape and size of the stigma and the teeth at the tip of the ovipositor.
Distribution
Megastigmus aculeatus is a cosmopolitan species, found all over the world where Roses thrive.
Reproduction
Most species in the genus Megastigmus are known to reproduce by thelytokous parthenogenese, meaning that unfertilized eggs will produce females. The ratio of males to females is usually well under 7%, in many populations even 0-2%References:
Some text fragments are auto parsed from Wikipedia.
Roques & Skrzypczyńska (2003) Seed-infesting chalcids of the genus Megastigmus Dalman, 1820 (Hymenoptera: Torymidae) native and introduced to the West Palearctic region: taxonomy, host specificity and distribution. - Journal of Natural History, vol.37, pp.127-238.