Arachnologische Mitteilungen 54

22 Y. Zvik ted were immature under 1 cm long and the rest where sub- adults and adults with a maximum length of 2.1 cm (anterior carapace margin to tip of telson). All individuals of Birulatus were found exclusively around Messor ebeninus nest openings, or on their active foraging trails, and demonstrated a unique behaviour of pausing and allowing the ants to check them frequently (Fig. 2). In at least six instances, scorpions were observed going in and out of the nest itself, disregarded by the ants. Beside scorpions of the genus Birulatus , six other scorpion species where found regardless the presence or absence of Birulatus : Androctonus crassicauda Olivier, 1807 (20 individuals), Leiurus hebraeus (Bi- rula, 1908) (~300 individuals), Compsobuthus schmiedeknechti Vachon, 1949 (10 individuals), Compsobuthus carmelitis Levy, Amitai & Shulov, 1973 (6 individuals), Scorpio palmatus Eh- renberg, 1828 (~150 individuals) and Nebo hierichonticus Si- mon, 1872 (10 individuals). The scorpions from the different species observed in the field appeared to avoid close encoun- ters with the ants, and in one case a young L. hebraeus that approached the nest was immediately attacked by the ants. Of 20 ant nests observed, ten contained remains of dead Birulatus or parts of their exuvia, even at times when live spe- cimens were not found around the nest. In two incidents, ants were observed carrying a dead, dry body of Birulatus out of the nest. Most of the scorpion remains were recovered from orga- nized piles of dead ant bodies, suggesting that the ants treat the scorpions the same as they treat other nest member ants. Discussion These observations offer some primary evidence for a myrme­ cophilous relationship between Birulatus sp. and Messor ebeni- nus , the first such relationship ever recorded. During the field observations, no aggressive or negative interactions were ob- served between the Birulatus scorpions and the ants.The ants neither attack, nor serve as prey for the scorpions. How the scorpion avoids being attacked by the ants remains to be de- termined. Possible benefits to the scorpions from the relation- ship might include the following: 1. The Messor nest is a well-protected, environmentally-sta- ble and resource-rich space, which may provide a suitable shelter (Kronauer & Pierce 2011). Large colonies provide a greater variety of microhabitats and can sustain larger and more stable populations of guests over longer time periods (Kronauer & Pierce 2011). 2. Ant colonies are well defended, so from the perspective of a myrmecophile, they provide an ‘enemy free space’ (Kronau- er & Pierce 2011). 3. Colonies of M. ebeninus can persist for a long time, as some queen ants are known to live up to 30 years ( Jemielity et al. 2005), perhaps offering a long-term environment for the scorpions. Although it is unlikely that individual Birulatus scorpions live for more than a few years, the possibility of successive generations cohabiting a single ant nest should be investigated. 4. Ant species with large colonies can harbour a high diver- sity of myrmecophiles (Pérez-Lachaud & Lachaud 2014), which in turn may serve as potential prey for the scorpions. The scorpions may also feed on the ant eggs and larvae as with some other myrmecophiles (Kronauer & Pierce 2011, Hölldobler & Wilson 1994). Possible advantages to the ants from this relationship re- main unclear, but perhaps the scorpions control the number of parasitic myrmecophiles or predators in the nest. The observations described above suggest the existence of a positive interaction between B. israelensis scorpions and M. ebeninus ants. Further research is required to explore the nature of the relationship and whether other Birulatus species are also associated with ants or with other burrowing organisms. Fig. 2: Birulatus israelensis Lourenço, 2002 pauses on the ant trail and lets an ant examine it with her antennae (photo Yoram Zvik)