FOOD AND WATER-RESOURCES USED BY THE MADAGASCAN HISSING-COCKROACH MITE, GROMPHADORHOLAELAPS SCHAEFERI

We determined the food source and water balance properties of the hiss ing-cockroach mite, Gromphadorholaelaps schaeferi. The food source for mites was identified using Evans blue dye by direct injection into a fasting host cockroach, Gromphadorhina portentosa, or by incorporation into cockroach food. No coloration was observed in mites on dye-injec ted cockroaches, but coloration was present in mites when only the foo d for the cockroaches had been stained. Thus, the mites are scavengers of cockroach food, and are not parasitic as previously thought. Our r esults demonstrate that the mites can absorb water from the air anywhe re between 0.84 and 0.93 a(u)psilon (%RH/100), and wax-block experimen ts revealed that the mouth is the site of uptake. The mites are normal ly clumped together on the host, typically in between the cockroach's legs and around the spiracles. Water loss rates for mites in groups (0 .16% h(-1)) were far lower than for isolated mites (0.30% h(-1)), sugg esting a 'group effect' with regard to water balance. Above the transi tion temperature of 30 degrees C rate of water loss was rapid. The sit es occupied by mites on the cockroach's body seem to be highly specifi c for feeding and absorption of water vapour.