Nutritional requirements of flea larvae, and their bearing on the specific distribution and host preferences of the three indian species of Xenopsylla (Siphonaptera)

Abstract

The comparative nutritive value of dried horse blood, highly milled wheat flour devoid of bran, a mixed diet of blood and wheat flour and that of blood and yeast for the larvae of Xenopsylla cheopis, X. brasiliensis and X. astia was ascertained experimentally. Pure blood proved inadequate, probably because it is deficient in accessory food factors. The growth of their larvae on wheat flour alone was erratic; only partial success was obtained, and the adults emerged after long and irregular intervals. This I attribute to the association of micro-organisms, possibly fungi, with this food. A mixture of blood and wheat flour quickened their larval development, but it was not a satisfactory larval diet. Blood and yeast form an ideal food for all flea larvae.It is concluded that larval diets, containing blood or wheat proteins and vitamins of the B group, are essential for the successful rearing of these rat-fleas, and that the proper sclerotization of the adult is due to the presence of haemoglobin in the larval food. The available data on the effects of diverse diets on the growth of flea larvae lend strong support to the conclusion that successful development depends on the presence of these vitamins in the food; it also leads me to think that their source in nature may be the association of micro-organisms with the food.The larval food appears to be an important factor that governs the distribution and host preferences of different species of flea. The larvae of X. astia require the most nutritive diet. If a rich larval food is present in a rodent burrow, X. astia flourishes, as in the burrows of Tatera indica and Bandicota malabarica, and even in those of the domestic rats in certain regions. In contrast, the nutritional requirements of the larvae of Xenopsylla cheopis and X. brasiliensis are simple; thus they prosper readily in a burrow of the domestic rat, even where the nutritive value of the larval food is very low. As the temperature tolerance of X. brasiliensis is the lowest, this species is confined to some of the cooler regions.The irregular distribution of the three species of rat-fleas inside India may be related to differences in the nutritional value of the varied organic sub stances found in rat burrows in different plaoes. The fact that the distribution of X. cheopis and X. brasiliensis is wider than that of X. astia is attributed to the ability of the larvae of the first two species to grow better on flour alone; this possibly enables them to survive transport in grain, even without rats, to places far from their original home.