Accurate morphological ant mimicry by Myrmarachne jumping spiders confers strong protective benefits against predators. However, it has been hypothesized that the slender and constricted ant-like appearance imposes costs on the hunting ability because their jumping power to capture prey is obtained from hydraulic pressure in their bodies. This hypothesis remains to be sufficiently investigated. We compared the jumping and prey-capture abilities of seven Myrmarachne species and non-myrmecomorphic salticids collected from tropical forests in Malaysian Borneo and northeastern Thailand. We found that the mimics had significantly reduced abilities compared with the non-mimics. The analysis using geometric morphometric techniques revealed that the reduced abilities were strongly associated with the morphological traits for ant mimicry and relatively lower abilities were found in Myrmarachne species with a more narrowed form. These results support the hypothesis that the jumping ability to capture prey is constrained by the morphological mimicry and provide a new insight into understanding the evolutionary costs of accurate mimicry.
A new species of the genus Castoponera Deeleman-Reinhold, 2001, Castoponera christae sp. n., is described here. The species is closely related to Castoponera lecythus Deeleman-Reinhold, 2001, but can be distinguished by the structures of the male palp and the female genitalia.
The genus Myrmarachne MacLeay, 1839 (Araneae: Salticidae) is one of the most diversified salticid groups in Southeast Asia, with 23 species previously recorded from Borneo. Based on the collections accumulated from 2004 to 2014 in the Lambir Hills National Park, we herein describe six new species: M. amabilis sp. nov., M. hashimotoi sp. nov., M. lagarosoma sp. nov., M. leptosoma sp. nov., M. salaputium sp. nov. and M. tintinnabulum sp. nov. In addition, we describe the female of M. endoi Yamasaki Ahmad, 2013 for the first time. The male-female combination in M. amabilis sp. nov., M. tintinnabulum sp. nov. and M. endoi were confirmed by DNA barcoding.
The genus Utivarachna Kishida, 1940 currently comprises 23 species, with eight described from Borneo. We examined the type materials of the Bornean species, except for U. fukasawana Kishida, 1940, as well as newly collected specimens. As a result, we describe a new species, Utivarachna itiokai sp. nov., which belongs to the dusun-group. We also provide the first description of the female of Utivarachna ichneumon and redescribe the known Utivarachna species of Borneo.