Among the insects, sublethal pesticide doses are known to affect general activity. Low doses of malathion, for example, increase walking speed of wasps, while other compounds cause continuous wing-fanning and/or flight (Haynes 1988). Among some mites and ticks formamindine compounds affect dispersal by increasing locomotion (Knowles 1987). Observations in our laboratory suggested that dosed spiders were more active than control animals.

SEE Lynaphia communis HERE

To test this assumption, software was written so a computer-driven camera could follow up to 10 individual spiders over 24-hour periods under natural photoperiod. Data have been collected for the lycosids Schizocosa ocreata and Rabidosa rabida, the salticid spider S. scenicus, the theridiid Achaearanea tepidariorum and a linyphiid (Frontinella pyramitella). The system records the time and distance an animal moves (including movements in place such as grooming). The activity levels are then analyzed using both conventional and circular statistics. The artificial intellegence routines used for this appication are specific to my recording equipment. A manual program is available to input analyze movements recorded in AVI format. You may request a copy by e-mailing me  (btietjen@bellarmine.edu)

Adults of all species showed both higher activity and a shift in peak activity when dosed with malathion. Changes in a spider’s total activity and peak activity time are likely to affect the time budgets of the dosed animals (Cloudsley-Thompson 1960). The data shown above are for the lycosid, Rabidosa rabida.

These tracings show the paths taken by normal and dosed Schizocosa ocreata during a ten-minute run. Note the obvious change in activity following exposure to malathion. These data also suggest that dosed spiders would increase their metabolic rate. Anderson (1970) suggested that two lycosids show diurnal variation in their metabolism, but his data were limited to a single 24-hour cycle. In general, he found that spider metabolic rates were lower than other similar-sized poikilotherms, and he suggested that the low metabolism of spiders may be an adaptation to cope with an inconsistent food supply. We suspect that the low metabolism may also be partly responsible for the relative insensitivity of spiders to various insecticides (while spiders were usually dosed in the 10^-4 to 10^-7 range, while our test insects were dosed with 10^-8 to 10^-12 malathion). If metabolic rates increase as expected, this may further compromise their chances for survival; especially since prey capture appears to be adversely affected by pesticide exposure.

For all tested species, spiders became active earlier in the day which may cause them to forage when competitors or predators are present, or could have them active when their normal prey are unavailable.

Field data collected by our laboratory through an arrangement with the Kentucky State University Research Farm, suggests that S. scenicus adjusts its’ time budget so their peak activity coincides with that of their primary prey on the surface of grain bins (the Angoumois grain moth, Sitotroga cerealella, typically exit grain bins through top vents about 14:00). During peak hours, 47% of grain moths on the bin surface were being fed upon by S. scenicus (over 1200 grain moths were scored). The shift of over an hour by dosed spiders would cause them to forage outside the observed peak activity of their prey.