G Díaz

Artificial feeding in Boophilus microplus (Acari:Ixodidae) through micropipettes.

Abstract: Newly molted Boophilus microplus females obtained in a laboratory at 30°C and environmental relative humidity (RH) were employed. An original device was used to hold ticks during feeding. Three groups of 15 ticks each were created: unfed, fed with heparinized blood, and fed with defibrinated blood. Ticks were weighed before and after feeding. Females were restricted by group in three isolators attached on the skin of a bovine. Ten sexually competent males were added to each isolator. Time of coupling, tick mortality, time of detachment, and weight of engorged ticks were determined. Engorged females were incubated at 30°C and 100% RH. Periods of nonparasitic phase, laying efficiency, and fertility of eggs were noted. There were no statistical differences between the three groups. This means that feeding with micropipettes does not affect the non‐parasitic phase of B. microplus, the differences between heparinized and defibrinated blood are not significant.

Thermal constant estimation in tropical horse tick, Anocentor nitens (Acari:Ixodidae).

Abstract: Experience has demonstrated that the exclusive use of acaricides as a control method against cattle ticks causes several problems, and is not totally effective. Other methods need to be added in order to achieve better and more profitable control of these parasites. Groups of 12 to 15 engorged ticks, bred on bovines, were individually incubated at six temperatures (T= 24, 26, 28, 30, 32, and 34°C) and four relatives humidities (RH= 100, 80, 75.5, and 70%), creating 24 variants. The onset of oviposition and eclosion (emergence of larvae from eggs) was observed in all ticks, and preeclosion times (PET) were determined. A linear regression equation for the velocity of development with temperature as a function of the inverse of PET was calculated for each RH value. For each RH the minimum thermal threshold (MTT) was obtained by extrapolation and the effective temperature summation (ETS) calculated from the equation (incubation temperature − MTT) × PET. The four MTT values obtained were not significantly different; the mean value of MTT was 15.25°C. The thermal constants did not prove to be not statistically different over the range of RH values employed in the experiments, the mean being 354.04°C‐day.

Age and Weight Relationship in Boophilus microplus (Ixodoidea: Ixodidae) Larvae

The study of the age of free-living stages of ticks is not a frequent subject in acarology research. Baseline knowledge and some possible applications both in research and in tick control are to be considered. Sixty engorged females were incubated at 28 +/- 1 degrees C and 100% relative humidity. Age zero of larvae was established at 10 days after the beginning of eclosion. Larvae were weighted in paper envelopes in groups ranging from 150 to 400 each. Live weight means (LWM) and dry weight means (DWM) were obtained. All larvae have defecated at age zero. Maximum survival was 57 days. Larval age was also expressed as effective temperature summings (ETS). LWM declines slightly with age. DWM has a linear relationship to age from 0 to 504 degrees C-day with a determination coefficient of 0.95. Absolute water content increases from 0 to 504 degrees C-day; further water content diminishes. Dry matter weight declines just to 504 degrees C-day of age. It might be theoretically possible to estimate the age of larvae in pasture by weighing groups of them.