Daily activity, thermoregulation and water loss in the tiger beetle Cicindela hybrida

Abstract

1. The tiger beetle Cicindela hybrida is a diurnal predator inhabiting open sandy areas. The activity pattern on a sunny day in May with a mean maximum surface temperature of 40°C is described (Fig. 2). The inactive period is spent in burrows in the sand and it is suggested that a threshold of 19°C releases the daily round of activity (Fig. 5). The animals appear on the sand between 7.00 and 10.00 and the number reaches a maximum at 34-42°C (surface temp.). The duration of the activity period is indirectly determined by the number of available prey which is maximal at 36°C and decreases both at higher and lower temperatures. Mean onset and termination of activity occur at about 28°C (surface temp.) when the expected capture rate is 3 per hour. In actograph experiments, onset was controlled by the illumination and occurred several hours before "dawn" (Fig. 9). 2. The preferred body temperature is at about 35°C and thermoregulatory behaviour patterns are used in order to approach this. At low ambient temperatures, body temperature is increased by sun-basking, while at high temperatures stilting is used to prevent it from increasing above 35°C. If the temperature becomes intolerably high, the animals dig into the sand (Figs. 8, 16). Measurements of body temperatures in the field show that tiger beetles have partial regulation (Fig. 10) and it is suggested that this is because the cost of thermoregulation is low, but prey is not abundant enough to allow a full exploitation of this, and predation (hunger) interferes with the thermoregulation. 3. An estimation of the daily water loss under field conditions is presented based on measurements of the water loss in the laboratory at different temperatures and relative humidities. These values are weighted by the times actually spent at different combinations in the field (Figs. 17, 19). The loss amounts to about 10% per day of initial body weight, and it is concluded that tiger beetles have not evolved any special adaptations with respect to this factor.

Distribution and habitat preferences of tiger beetles (Coleoptera: Cicindelidae) of the riverine ecosystems of Sri Lanka

“…When considering the habitat preferences tiger beetles, were found foraging at air temperatures of 35.13±0.53 0 C. Tiger beetle activity is highly dependent on air temperature and many species display maximum activity at an optimal temperature range that is decided by thermoregulatory mechanisms, desiccation and prey availability (Dreisig 1980;Schultz & Hadley 1987). Our data suggests that the optimal temperature range of the riverine tiger beetles lies between 31.00-41.00 0 C. Tiger beetles are also sensitive to soil moisture, soil salinity and soil temperature of locations due to preferences in oviposition and larval development (Romey & Knisley 2002;Cornelisse & Hafernik 2009).…”

A comparative study of ultrasound‐triggered behaviour in tiger beetles (Cicindelidae)

“…The radiation of tiger beetles away from the tropics was, however, accompanied and/or facilitated by a shift to spring±autumn activity peaks in some species (Vogler & Goldstein, 1997). Studies of their thermal biology have shown that most cicindelids are adapted for activity at high temperatures (> 30 8C) and routinely operate near their upper thermal limits (Dreisig, 1980;Pearson & Lederhouse, 1987). Even though they can maintain their body temperature slightly above ambient (Dreisig, 1984), their movement is largely curtailed at air temperatures below 20 8C (Morgan, 1985;Pearson & Lederhouse, 1987;Knisley, Schultz & Hasewinkel, 1990).…”

Field analyses of insect heat budgets: Reflectance, size and heating rates

“…Although the present documentation of insect heat budgets is so poor, there has been much recent work on their thermal ecology and energy balance (cf. Edney 1971 ;Casey 1976;Dreisig 1980;and review by May 1979), and though in some cases this has included spot measurements of body temperatures many other studies have relied on assumptions about rates of heat exchange, and the effects of size, shape or colour thereon, which are poorly substantiated. There is thus a recognized need for a realistic consideration of the effects of insect size (weight, and/or linear dimensions) and of colour (determined by emissivity or reflectance of the surfaces) on the rates of heating and cooling of insects, and on the temperature excesses which they may attain in sunny conditions.…”