Cotesia parasitoids and sex determination

Competition between Cotesia parasitoids.
Both Cotesia glomerata and C. rubecula were introduced from Europe to North America to control the imported cabbageworm – Pieris rapae.  C. glomerata was introduced in the mid-1800’s and C. rubecula in the late 1900’s and this latter species is now displacing C. glomerata in much of the continent and appears to be providing better pest control in the process.  Competitive displacement of one parasitoid by another in the context of biological control is a particularly fascinating outcome that is often tied to slight differences in the behavior, ecology or genetics of the species.  We are testing a number of hypotheses for the displacement of C. glomerata by C. rubecula.  One of these hypotheses involves differences in the sex determination method employed by the two species. 

C. rubecula
Cotesia glomerata.