Ethanol fuel improves pitfall traps through rapid sinking and death of captured orthopterans.

The choice of killing solutions for pitfall traps can influence sampling and is highly dependent on the objectives of each study. It is becoming increasingly common, however, and is more environmentally friendly, to use the same organisms to extract information for different kinds of studies. The killing solution should, therefore, be able to sample local active organisms, as well as maintain the integrity of their organs, tissues, and macromolecules. In a previous work, we showed that using ethanol fuel as a killing solution maintains the integrity of the specimens and enhances the Orthoptera richness and abundance of samples. In the current study, we evaluated two explanations for this pattern. We set up a field experiment to test whether ethanol fuel is attractive for orthopterans, and we investigated in the laboratory whether individuals of Gryllus sp. sink or die faster in ethanol fuel than in other killing solutions. Our results allowed us to refute the hypotheses of attraction caused by ethanol fuel and showed that the higher sampling efficiency of ethanol fuel is directly linked to the specimens sinking and dying faster than in other killing solutions. Thus, in addition to taxonomic, anatomical, and molecular studies, we recommend ethanol fuel for sampling organisms active in the litter in ecological studies.