Stem borer and parasitic wasp. Larva of an African pink stem borer (Sesamia calamistis) with the parasitic wasp Cotesia sesamiae. The larvae of the Sesamia calamistis moth feed on a wide range of plants, boring into the plant stems. The crops affected include rice, millet, sugar cane, wheat and maize. It is found in many tropical and subtropical regions of Africa. Its numbers can be reduced by use of the parasitic wasp Cotesia sesamiae, a form of biological pest control. The wasp lays its eggs in the larva and the hatching and development of the wasp kills the larva.