Distribution, biology and ecology of Dentichasmias busseolae Heinr. (Hym., Ichneumonidae), a pupal parasite of graminaceous stem-borers (Lep., Pyralidae)

Dentichasmias busseolae Heinr., an important pupal parasite of Pyralid graminaceous stem-borers in East Africa, is widely distributed in the Ethiopian Region but is more abundant in areas with an equatorial humid climate. In the laboratory adults mated immediately after emergence and started oviposition the same day. The female oviposits only in a borer pupa without a cocoon in a stem, and oviposition is stimulated by the presence of the frass of Chilo partellus (Swinh.) larvae. D. busseolae does not attack Busseola fusca (Fuller), Sesamia calamistis Hmps. or Eldana saccharina Wlk. in the field but these were accepted for oviposition when exposed in C. partellus pupation tunnels or with frass of C. partellus larvae, and were suitable for development. D. busseolae could complete its development in one- to eight-day-old C. partellus pupae when the pupal period of C. partellus was 10·5 days. The life-cycle was completed in 15–19 days at a mean temperature of 25°C, but could not be completed at a constant temperature of 30°C; temperatures fluctuating between 22°C and 30°C were not detrimental. At Namulonge (Uganda) percentage parasitism showed a positive correlation with rainfall, with a lag of about a month.

Notes on the distribution and biology of Pediobius furvus (Gah.) (Hym., Eulophidae), a parasite of graminaceous stem-borers

Pediobius furvus (Gah.) (Eulophidae) is a parasite of the pupae of Pyralid and Noctuid stem-borers on graminaceous crops in Africa between 17°N and 17°S. It co-exists with the other pupal parasites Dentichasmias busseolae Heinr. and Procerochasmias nigromaculatus (Cam.) (Ichneumonidae) and Hyperchalcidia soudanensis Steffan (Chalcididae), but it is more abundant below 4000 ft where P. nigromaculatus does not occur. Mating follows a courtship dance, and oviposition occurs in any part of the host pupa. The life-cycle is completed in 18–20 days at 30°C, and up to several hundred adults may emerge from a single host pupa, the most suitable pupae being 2–3 days old at the time of oviposition. Longevity was improved when sucrose was provided as food. Host pupae outside the stem were parasitised, but puparia of Diptera and cocoons of Apanteles sesamiae Cam. (Braconidae) were not parasitised in the laboratory. Pupae formed inside cocoons were not attacked. Pediobius furvus has become established in Madagascar on Sesamia calamistis Hmps, and is considered promising for biological control of graminaceous stem-borers in other countries.