Stomorhina lunata has long been recognized as an important egg-predator of locusts in many parts of Africa, but there has been little work on its biology or its importance in the natural control of locusts. Field work on S. lunata as an egg-predator of the Desert Locust, Schistocerca gregaria Forskål (Orthoptera: Acrididae), was carried out in eastern Africa.
The life history, from oviposition to dispersal of the resulting adults, is described, and typical observations suggesting the importance of olfaction in the location of hosts, and in inducing oviposition, are described and discussed. The method of feeding by the larvae is such that an infested locust egg-pod is usually wholly prevented from hatching. Quantitative data show that superpredation is rare; that the distribution of infested egg-pods within an egg-field is affected by the grouping of the egg-pods; and that differences of topography, soil and vegetation usually have little effect on the degree of predation. The time at which an egg-field is laid during the course of a locust infestation affects the degree of infestation by S. lunata.
Observations on S. lunata caged in the field showed that pollen and sugar solution are essential for the survival of adults and for the maturation of females.
There is little mortality among eggs and larvae of S. lunata, but pupae are parasited by Dirhinus excavatus Dalman (Hymenoptera: Chalcididae) and an aleocharine (Coleoptera: Staphylinidae), and emerging adults are preyed upon by birds to a considerable extent.
The known hosts of S. lunata are listed, the distribution of the fly is shown on a map, and data on the morphometrics of adults from various sources are given. These matters are discussed in relation to the possible means of survival of the fly in the absence of swaming locusts, and to the possible means whereby large numbers of mature females appear at the time of oviposition by locust swarms; it is suggested that migration and alternative foods may both be important.
It is concluded that S. lunata is the most important insect enemy of the Desert Locust in eastern Africa.
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