Dimorphic Jumper & Loxocera

Photographed in situ [1]

A dimorphic jumping spider (Maevia inclemens) rips the wing base off a tiger crane fly (Nephrotoma sp) twice its size. Females like this individual are characterized by two bright red lines on the abdomen, while males have two morphs: (1) a gray morph with striped legs and orange pedipalps, and (2) a tufted morph with a black body, light-colored legs, and three hair tufts above the eyes. Females exhibit different behavioral and phenotypic preferences in each of the two morphs. In gray morphs, females are more likely to mate with males that have poorer body conditions but perform more vigorous courtship displays. On the other hand, females prefer tufted morphs of greater body mass with more cautious courtship displays. Under this sexual selection regime, variation in female preference has likely maintained and promoted divergence in male phenotype.

However, differences in visibility throw another angle at understanding male courtship behaviors. Gray morphs are substantially greater in body size, and at close distances are more easily detected by females when performing their courtship display, which consists of jagged shuffling movements. Tufted morphs instead rear up in place and wave the forelegs and pedipalps wildly, which makes them more conspicuous at farther distances. This trade-off in visibility at different distances between the two morphs not only has implications for mating success, but also for susceptibility to predation. One study found that on average, gray morphs were at a greater risk of detection by predatory arthropods such as the bold jumping spider (Phidippus audax). Accordingly, in the presence of a predator, gray morphs court females less often and more cautiously than tufted morphs— contrary to what would be expected based on female preference.

I’ve been wanting to photograph these tiny orange flies (~8-12 mm long) for a while, but usually they are just a little too skittish. This species belongs to the rust fly family (Psilidae: Loxocera cylindrica) and as larvae feed on sedges and rushes. One interesting characteristic of psilids is their third antennal segment, each often bearing a slender antenna-like arista. Photographed after pursuit [3]

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