The development of Loa Loa (Guyot) in Chrysops Silacea (Austen) and in Chrysops Dimidiata (van der Wulp)

Abstract

The life-cycle of L. loa has been worked out in two species of Chrysops in Nigeria, C. silacea and C. dimidiata, 358 experimentally infected flies having been examined. The metamorphosis takes ten to twelve days for completion. Development takes place in the muscular and connective tissue, principally in the abdomen of the fly, but also in the thorax and the head. There are three main phases after the embryo has cast its sheath and penetrated the stomach wall. During the first place, which continues for three days, the young larvæ broadens considerably. In the second phase, which occupies another three days, the worms begin to lengthen more than they broaden; and in the third phase there is a rapid lengthening, with little or no increase in breadth. An ecdysis occurs on the sixth day, after which the larva has a trilobed instead of a pointed sickle-shaped tail. From the seventh day onwards the larv˦ are able to travel from one part to another, and by the tenth day they are congregated in the head, mainly at the root of the proboscis. The larva, during its development, increases its length tenfold. A striking feature is the disparity in the size of the developing forms, which is explained by the delay of many of the embryos in the stomach. Sheated and active embryos have been found in that organ for as long as three days after the infecting feed.