Studies on the non-parasitic stages of the cattle tick, Boophilus microplus (Canestrini) (AcarinaL Ixodidae)

Abstract

Laboratory studies of the effects of temperature and relative humidity on the non-parasitic stages of the cattle tick, Boophilus microplus (Canestrini), are described. The pre-oviposition period ranged from 19-39 days at 59-60�F to 2-3 days at 97�F. The duration of oviposition was uninfluenced by relative humidity but varied from a maximum of 44 days at 59�F to a minimum of 4 days at 102�F. The minima at each temperature were exceedingly irregular, due to the deaths of ticks. The number of eggs laid by a female tick was uninfluenced by relative humidity. The peak oviposition mean of 2496 eggs per female occurred at 75�F, fewer eggs being laid at higher and lower temperatures. Daily egg output attained a maximum of 197 at 92�F, but was uninfluenced by relative humidity. The water loss of engorged female ticks was greatly affected by inert dusts and even dusting with a sample of soil chosen at random produced a significant increase in water loss. Developmental period was uninfluenced by order of deposition, but percentage hatch of eggs laid during the last few days of oviposition is lower. Eggs did not hatch at constant relative humidities lower than 70 per cent., but some were able to survive relative humidities lower than this if exposed periodically to a saturated atmosphere. The period of development of eggs varied from a maximum of 146 days at 62�F to a minimum of 14 days at 97�F. Maximum hatch occurred between 85 and 95�F, and at relative humidities above 95 per cent. Exposure of eggs to temperatures below the developmental zero prolonged the period of development merely by the period of exposure. Regular alternation of temperature between the limiting temperatures of 59 and 97�F with a steady rise or fall between the extremes resulted in development at a rate approximately equal to that obtained at constant temperature of 78�F, the arithmetic mean of the above figures. Larval longevity was influenced markedly by temperature and humidity. A maximum of 240 days was recorded at 72�F and 90 per cent. relative humidity. Larvae are able to recoup water losses sustained at low relative humidity by absorption from the atmosphere during subsequent periods of high relative humidity.