FEEDING NYMPHS OF HYALOMMA-TRUNCATUM (ACARI, IXODIDAE) ON GUINEA-PIGSPREVIOUSLY EXPOSED TO NYMPHS

The ability of nymphal Hyalomma truncatum Koch to feed on guinea pigs previously exposed to nymphal ticks was studied by measuring the perce ntage of ticks engorging and molting, their engorged weight, and hemog lobin content. Four guinea pigs were infested with 20, 40, 80, and 200 nymphs, respectively, on three occasions at 21-d intervals, followed by a fourth infestation after another 21-d interval with 100 nymphs. G uinea pigs originally infested with 20 and 80 nymphs were infested a f ifth time with 100 nymphs 3 mo after the fourth infestation. Guinea pi ps originally infested with 40 and 200 nymphs were infested a fifth ti me with 100 nymphs 6 mo after the fourth infestation. There was a sign ificant decrease, below infestation I levels, in the number of ticks e ngorging on each guinea pig during infestations IV and V. Whereas all nymphs molted after infestation I, the percentage of nymphs molting af ter infestation V ranged from 0 to 34%. For ticks infested on each of the guinea pigs, the percentage molting after infestations III-V were significantly lower than those observed after infestation I. A signifi cant decrease in the mean weight of engorged ticks was observed starti ng at infestation III. Mean hemoglobin content of ticks declined signi ficantly at infestation II. The response elicited by feeding nymphs ap peared to last at least 6 mo.