Pteromalus puparum (L.)
Geographic distribution: Cosmopolitan.
Morphology: Females are shiny black with metallic, blue and green, hues, about 3-4 mm in length.
Life history: Pteromalus puparum is a an endoparasitoid of the pupae or prepupae of many Lepidoptera. Prior to oviposition females gauge the size of the host-pupa and then regulate the number of eggs (up to 100-200, depending on host-pupa) inserted therein, along with a venom (toxin). The size of emerging adults decreases, and their development times shorten, with an increase in the number of parasite larvae/host-pupa. Parasitization causes the color of the host-pupa to change from green-gray to dull brown, as the parasite larvae develop. Complete adult emergence may take 2-3 days or more, and the sex ratio is about 6 females to 1 male. The adults are weak fliers, feed on flower nectar and may live for several weeks.
Economic importance: In the Middle East P. puparum is a parasitoid of Pieris brassicae and of P. rapae. Rates of parasitism may approach 50%, but as only the prepupae or pupae are attacked, the larvae are not affected and continue to feed and damage the crops. The benefits of P. puparum are in reducing the adult population, which impacts on the size of later generations.
Up to 37.5% of field populations of P. puparum may be infected by a virus that increases adult longevity, reduces the number of females but apparently does not reduce successful parasitism. Parasitized pupae may also be affected by the Entomopathogenic fungus Beauveria bassiana (Bals.) Vuill.
Parasite prepupae within P. rapae pupae were stored at 10°C and 80% R.H. for periods of up to 15 months and still produced viable progeny.
Abbas, M.S.T. and El-Dakroury, M.S.I. 1985. Studies on Pteromalus puparum L. (Hymenoptera: Pteromalidae), a pupal parasite of the cabbage worm Pieris rapae L. (Lepidoptera: Pieridae) in Egypt. Zoosystematics and Evolution 61: 339–344.
Bouletreau, M. and David, J. 1967. Influence de la densité de population larvaire sur la taille des adultes, la durée de développement et la fréquence de la diapause chez Pteromalus puparum L. [Hym., Chalcidien]. Entomophaga 12: 187-197.
El-Sufty, R. 1988. Biology of Pteromalus puparum L. (Hymenoptera: Pteromalidae) in pupae of the cabbage white butterfly infected with fungus Beauveria bassiana (Balsamo, Vullemin). Journal of Agricultural Research, Tanta University 14: 1261-1271.
McDonald, R.C. and Kok, L.T. 1990. Post-refrigeration viability of Pteromalus puparum (Hymenoptera: Pteromalidae) prepupae within host chrysalids. Journal of Entomological Science 25: 409-413.
Ragab, M.E. 1992. Ecological and biological studies on the parasitoids of the cabbage white butterfly, Pieris rapae (L.) (Lep., Pieridae) in winter cabbage at Mansour. Journal of Applied Entomology 113: 513–517.
Razmi, M., Karimpour Y. and Safaralizadeh, M.H. 2011. Parasitism of Pieris brassicae (L.) (Lep.: Pieridae) on cabbage farms in comparison with wild hosts and study on use of Pteromalus puparum (L.) (Hym. Pteromalidae), as a biological control agent versus this pest. Munis Entomology and Zoology 6: 176-180.
Takagi, M. 1987. The reproductive strategy of the gregarious parasitoid, Pteromalus puparum (Hymenoptera: Pteromalidae). 2. Host size discrimination and regulation of the number and sex ratio of progeny in a single host. Oecologia 70: 321-325.
Wang, F. (and 9 co-authors). 2017. A novel negative-stranded RNA virus mediates sex ratio in its parasitoid host. Plos Pathogens 13: e1006201.
Zhu, J.Y. Ye, G.-Y and Hu, C. 2011. Venom of the endoparasitoid wasp Pteromalus puparum: an overview. Psyche 2011: 1-7.