Biologue

Article by
Barbara Baehr and Robert Raven, Queensland Museum, PO Box 3300 SOUTH BRISBANE QLD 4101

Ant Spiders are one of the most colourful, medium-sized (2.5 - 20 mm), day-active hunters in Austalia (Fig.1). Most species can be easily recognized by their bright yellow or orange spots on dark brown background on their back (Figs. 1,2). Their legs look like the spiders are wearing white, black and orange banded socks. Zodariids feed exclusively on ants. They live together with ants, mimicking their behaviour and sometimes even their chemical traits. For example, Habronestes bradleyi mimics ant pheromones so that ants can't recognized them (R. Allan et al., 1996). In Australia, the ant fauna is one of the most important components in all ecosystems. This could be the reason for the uniquely high diversity and the extreme evolutionary success of ant spiders in Australia. Recent surveys with pitfall traps in NT, WA, NSW and QLD have shown that ant spiders are one of the most dominant groups of all ground-living spider families in semi-arid and arid ecosystems.

With an estimated 300-350 species, Australia has the richest zodariid fauna worldwide. For the Australian continent only 19 species were described in the first 130 years of investigation. In the last 10 years, 55 new species have been described by B. Baehr, & R. Jocqué (1994, 1996, 2000) and R. J. Raven & B. Baehr (2000). Supported by this ABRS grant, 33 new species were described this year (B. Baehr, & R. Jocqué 2001; B. Baehr, & M. Gray submitted). Based upon our examination of museum collections, we estimate that only about 30% of the existing fauna is named.

The most important character by which to distinguish the different species is the male sexual organs ¾ the "male palps" ¾ which are extremely complicated in most genera. Before mating, the male uses the palpal organ to pick up the sperm discharged from the male genital aperture onto a tiny web. Hence, the sperm transfer is indirect. The structure of the palp is thought to bear some relationship to the structure of the female genital organ, the epigyne. However, the correspondence is minimal as often the female epigyne is externally quite simple. Hence, the many complex components of the male palp simply reflect species differences. Figs. 3 - 5 show male palps from the basic genus Pentasteron (Fig. 3) with a quite simple palp and more complex palps from the genera Habronestes (Fig 4.) and Euasteron (Fig. 5).

With the funding from ABRS, we are revealing the exciting world of ant spiders, describing the species and making them useful:

• for any survey undertaken to understand the biological diversity of the Australian invertebrate terrestrial fauna, because most of the ant spider species have a distinct distribution or occur only in distinct habitats;
• as "Indicator Species" in environmental conservation, because they are restricted to certain habitats as well as to certain ant species.

Literature cited:

Published papers resulted from ABRS funding:

Publication in press supported by ABRS funding:

Publication in preparation supported by ABRS funding: