50
Activity Patterns
Fig. 47. The short-term effect of varying temperature and relative air humidity on adult survivorship of the oribatid Scheloribates cf.latipes. Data were fitted by least squares.
the curve of the graph is obvious at about 65% relative humidity. The quadratic effect of temperature is highly significant, and the maximum rate of
faeces production is recorded at 20°C for every humidity level. A further
increase in temperature up to 25 °C results in decreasing feeding activity, and
the animals start moulting. It seems that in general a temperature of 25-27 °C
is the upper activity threshold for most Mediterranean arthropods. At higher
temperatures, feeding ceases and they enter a latent stage showing enhanced
resistance to heat.
Analogous observations concerning feeding activity as well as survivorship in response to varying temperatures and humidity have been made for
most oribatid and collembolan species sampled at Hortiatis. The combined
short-term effect of temperature and humidity on arthropod survival is
shown in Fig. 4.7. At low temperatures survivorship is independent of humidity, while at temperatures beyond 12°C arthropod survival depends upon the
humidity level. In general, different phenomena affecting animal survival,
such as cuticular transpiration, are insignificant below certain critical temperatures (Cloudsley-Thompson 1975).
The survival and feeding activity of arthropods commonly takes place
above a humidity threshold between 65 and 85% relative humidity. It seems
that, like their temperate relatives, the short-term response of the Mediterranean animals to air humidity is of the all-or-none type. The dependence of
activity on temperature appears to be more complicated. On the basis of data
gathered on Hortiatis it is possible to compile graphs showing the average
dependence of arthropod locomotory and/or feeding activity on temperature (Fig. 4.8). Relevant graphs are comparable to those describing the dependence of respiratory metabolism on temperature. Accordingly, graphs of
Activity Patterns
Fig. 47. The short-term effect of varying temperature and relative air humidity on adult survivorship of the oribatid Scheloribates cf.latipes. Data were fitted by least squares.
the curve of the graph is obvious at about 65% relative humidity. The quadratic effect of temperature is highly significant, and the maximum rate of
faeces production is recorded at 20°C for every humidity level. A further
increase in temperature up to 25 °C results in decreasing feeding activity, and
the animals start moulting. It seems that in general a temperature of 25-27 °C
is the upper activity threshold for most Mediterranean arthropods. At higher
temperatures, feeding ceases and they enter a latent stage showing enhanced
resistance to heat.
Analogous observations concerning feeding activity as well as survivorship in response to varying temperatures and humidity have been made for
most oribatid and collembolan species sampled at Hortiatis. The combined
short-term effect of temperature and humidity on arthropod survival is
shown in Fig. 4.7. At low temperatures survivorship is independent of humidity, while at temperatures beyond 12°C arthropod survival depends upon the
humidity level. In general, different phenomena affecting animal survival,
such as cuticular transpiration, are insignificant below certain critical temperatures (Cloudsley-Thompson 1975).
The survival and feeding activity of arthropods commonly takes place
above a humidity threshold between 65 and 85% relative humidity. It seems
that, like their temperate relatives, the short-term response of the Mediterranean animals to air humidity is of the all-or-none type. The dependence of
activity on temperature appears to be more complicated. On the basis of data
gathered on Hortiatis it is possible to compile graphs showing the average
dependence of arthropod locomotory and/or feeding activity on temperature (Fig. 4.8). Relevant graphs are comparable to those describing the dependence of respiratory metabolism on temperature. Accordingly, graphs of