Questing activity of larval cattle fever ticks, Rhipicephalus (Boophilus) microplus and R. (Boophilus) annulatus, in relation to photoperiod in south Texas

Photoperiodicity in questing activity has been reported for several tick species. For example, larval Ixodes scapularis quest at night because their host, deer mice, are nocturnal. Host seeking exposes ticks to environmental rigors of temperature, humidity, and predation. Hence, ticks often seek shelter between questing bouts, but ultimately must quest at times when encountering a host are most likely. To measure the periodicity of questing by Cattle Fever Tick larvae, we censused activity in 18 off-host populations simultaneously in south Texas pastures. Over a period of a week questing was measured four times at a different quadrant of the day-night cycle: sunset to midnight, midnight to sunrise, sunrise to midday and midday to sunset, with at least 24 hrs between censuses. For B. microplus, there were seven replicates to include all four seasons. For B. annulatus, there were 6 replicates that covered all four seasons. Populations were tracked so that each replicate was conducted when the populations were near peak. We found that both species quested morning, noon, and night with no significant differences related to the diurnal cycle. Similar results were reported for B. australis in Australia, correlating with our findings.