Influence of leaf litter moisture on the efficiency of the Winkler method for extracting ants

A preliminary checklist of soil ants (Hymenoptera: Formicidae) of Colombian Amazon

Background

This paper presents an updated list of soil ants of the Colombian Amazon collected in three different river basins: the Amazon, the Caquetá and the Putumayo. The list includes 10 subfamilies, 60 genera and 218 species collected from TSBF monoliths at four different depths (Litter, 0 - 10 cm, 10 - 20 cm and 20 - 30 cm). This updated list increases considerably the knowledge of edaphic macrofauna of the region, due to the limited published information about soil ant diversity in the Colombian Amazon region.

New information

This is the first checklist of soil ant diversity of the Colombian Amazon region. Six new records of species for Colombia are exposed: Acropygatricuspis (LaPolla, 2004), Typhlomyrmexclavicornis (Emery, 1906), Typhlomyrmexmeire (Lacau, Villemant & Delabie, 2004), Cyphomyrmexbicornis (Forel, 1895), Megalomyrmexemeryi (Forel, 1904) and Myrmicocryptaspinosa (Weber, 1937), most of them corresponding to subterranean ants.

Rapid extraction of invertebrates from tropical forest litter using modified Winkler apparatus

The Winkler extractor is widely used for collecting both micro- and macrofauna from large samples of forest litter, but the long period of extraction that it demands and that allows continuous feeding and reproduction of target organisms is a serious drawback when samples are collected for subsequent stable isotope analysis. This problem is exacerbated in a humid tropical climate. In this study, we assessed the effectiveness of the modified Winkler apparatus equipped with heating plates placed inside each mesh bag. The study was performed at the end of the wet season in a mature forest and young forest plantation at Cat Tien National Park, southern Vietnam. The heating plates increased the temperature within the extractors by about 8ºC and accelerated the desiccation of litter in the mesh bags. The extraction speed of macrofauna from the forest litter was strongly increased and the number of mites collected nearly doubled in the modified extractors, though the extraction rates of collembolans were not affected significantly. Overall, our results suggest that the application of heating plates accelerates the extraction process while yielding large quantities of litter-dwelling animals.