Incongruent molecular and morphological variation in the crab spider Synema globosum (Araneae, Thomisidae) in Europe

Establishing species boundaries is one of the challenges taxonomists around the world have been tackling for centuries. The relation between intraspecific and interspecific variability is still under discussion and in many taxa it remains understudied. Here the hypothesis of single versus multiple species of the crab spider Synema globosum (Fabricius) is tested. The wide distribution range as well as its high morphological variability makes this species an interesting candidate for re-evaluation using an integrative approach. This study combines information from barcoding, phylogenetic reconstruction based on mitochondrial CO1 and ITS2 of more than 60 specimens collected over a wide range of European localities, and morphology. The findings show deep clades with up to 6% mean pairwise distance in the CO1 barcode without any biogeographical pattern. The nuclear ITS2 gene did not support the CO1 clades. Morphological assessment of somatic and genital characters in males and females and a morphometric analysis of the male palp uncovered high intraspecific variation that does not match the CO1 or ITS2 phylogenies or biogeography either. Screening for endosymbiotic Wolbachia bacteria was conducted and only a single infected specimen was found. Several scenarios might explain these inconsistent patterns. While the deep divergences in the barcoding marker might suggest cryptic or ongoing speciation or geographical isolation in the past, the lack of congruent variation in the nuclear ITS2 gene or the studied morphological character systems, especially the male palp, indicates that S. globosum might simply be highly polymorphic both in terms of its mtDNA and morphology. Therefore, more data on ecology and behaviour and full genome sequences are necessary to ultimately resolve this taxonomically intriguing case.

Bassaniana birudis sp. nov., a new crab spider (Araneae, Thomisidae) from South Korea

The crab spider genus Bassaniana Strand, 1928 consists of six species mainly distributed in North America and Far East Asia. Two species of them, Bassaniana decorata (Karsch, 1879) and Bassaniana ora Seo, 1992, are known in Korea so far. A new crab spider, Bassaniana birudis sp. nov. is described, based on a male collected from Gumi-si, Gyeongsangbuk-do, South Korea. Distribution records are provided, as well as photos of habitus and illustrations of the male copulatory organ. The type specimens of this study are deposited in the collection of the Nakdonggang National Institute of Biological Resources (NNIBR) and Konkuk University (KKU), South Korea.

Masquerading predators deceive prey by aggressively mimicking bird droppings in a crab spider

In aggressive mimicry, a predator accesses prey by mimicking the appearance and/or behavior of a harmless or beneficial model in order to avoid being correctly identified by its prey. The crab spider genus Phrynarachne is often cited as a textbook example of masquerading as bird droppings in order to avoid predation. However, Phrynarachne spiders may also aggressively mimic bird droppings in order to deceive potential prey. To date, there is no experimental evidence to support aggressive mimicry in masquerading crab spiders, therefore, we performed a field survey, a manipulative field experiment, and visual modeling to test this hypothesis using Phrynarachne ceylonica. We compared prey-attraction rates among bird droppings, spiders, and control empty leaves in the field. We found that although all prey combined and agromyzid dipterans in particular were attracted to bird droppings at a higher rate than to spiders, other dipterans and hymenopterans were attracted to bird droppings at a similar rate as spiders. Both spiders and bird droppings attracted insects at a significantly higher rate than did control leaves. As predicted, prey were attracted to experimentally blackened or whitened spiders significantly less frequently than to unmanipulated spiders. Finally, visual modeling suggested that spiders and bird droppings can be detected by dipterans and hymenopterans against background leaves, but they are indistinguishable from each other. Taken together, our results suggest that insects lured by spiders may misidentify them as bird droppings, and bird dropping masquerading may serve as aggressive mimicry in addition to predator avoidance in P. ceylonica.

Phrynarachne birudis sp. nov., a new crab spider (Araneae, Thomisidae) from South Korea

The crab spiders of the genus Phrynarachne Thorell, 1869 comprising 32 species has been widely known to distribute worldwide to date. Only one species, Phrynarachne katoi Chikuni, 1955, is known in Korea so far. A new crab spider, Phrynarachne birudis sp. nov. is described, based on a male collected from Gumi-si, Gyeongsangbuk-do, South Korea. The geographic record is provided as well as photos of habitus and illustrations of the male copulatory organ. The type specimens of this study are deposited in the collection of the Nakdonggang National Institute of Biological Resources (NNIBR) and Konkuk University (KKU), South Korea.

Phrynarachne birudissp. nov., a new crab spider (Araneae, Thomisidae) from South Korea

The crab spiders of the genus Phrynarachne Thorell, 1869 comprising 32 species has been widely known to distribute worldwide to date. Only one species, Phrynarachne katoi Chikuni, 1955, is known in Korea so far. A new crab spider, Phrynarachne birudis sp. nov. is described, based on a male collected from Gumi-si, Gyeongsangbuk-do, South Korea. The geographic record is provided as well as photos of habitus and illustrations of the male copulatory organ. The type specimens of this study are deposited in the collection of the Nakdonggang National Institute of Biological Resources (NNIBR) and Konkuk University (KKU), South Korea.

Avoiding attack: How dune wasps leverage colour and motion to detect their cryptic spider predators

Ambush predators depend on cryptic body colouration, stillness and a suitable hunting location to optimise the probability of prey capture. Detection of cryptic predators, such as crab spiders, by flower seeking wasps may also be hindered by wind induced movement of the flowers themselves. In a beach dune habitat, as Microbembex nigrifrons wasps approach flowerheads of the Palafoxia lindenii plant, they need to evaluate the flowers and avoid landing on crab spider occupied flowers. Wasps may detect spiders through colour and movement cues. We tracked the flight trajectories of dune wasps as they approached occupied and unoccupied flowers under two movement conditions; when the flowers were still or moving. We simulated the appearance of the spider and the flower using psychophysical visual modelling techniques and related it to the decisions made by the wasp to land or avoid the flower. Wasps could discriminate spiders only at a very close range, and this was reflected in the shape of their trajectories. Wasps were more prone to making errors in threat assessment when the flowers are moving. Our results suggest that dune wasp predation risk is augmented by abiotic conditions such as wind and compromises their early detection capabilities.