Influences of the behaviour of epigeic arthropods (Diplopoda, Chilopoda, Carabidae) on the efficiency of pitfall trapping

Abstract

The behavioural response at pitfall traps and the attracting or repellent effect of fixing solutions were studied on seven species of epigeic arthropoda (Diplopoda, Chilopoda, Carabidae) in laboratory experiments. The tests were done individually with 30 males and 30 females (in exceptional case 20) under different illumination.

Tests with empty traps resulted in six different behavioural patterns. Their frequency was highly different between species as well as between sexes. It is remarkable that specimens of all species were able to avoid the traps or even rescue themselves out of the traps (with unlike skill). The behaviour pattern depends on visual and tactile inputs of the trap, the illumination and the characteristics of the specimens themselves.

Furthermore, four different fixing solutions (water, ethylene glycol, formaldehyde, acetic acid- ethanol-water-mixture) were tested. Only the mixture seemed to be repellent to millipedes and centipedes, but not to Carabidae. Attraction was not detectable for any of the species.

As a consequence of the very different behaviour pattern of specimens at the traps, it must be considered that pitfall trapping does not reflect the number of specimens being active in the surroundings of the trap. Therefore, this method is inappropriate for quantitative investigations of the arthropods living at a site (‘activity abundance’).