Is Picture Wing Fly a Predatory Jumping Spider Mimic?

The video of this picture wing fly (Delphinia picta) was recorded on April 24th 2011 in Athens, GA. It has a curious wing pattern which resembles a jumping spider but is it really?

Mimicry is a type of species interaction that evolves in response to prey, predators and parasites. Examples of mimicry is abundant in nature and provide compelling cases for natural selection. A classic example is Heliconius butterflies living in tropical America. Some Heliconius species show Batesian mimicry. Wing color patterns of unpalatable species (models) are selected in palatable species (mimics). High resemblance to toxic models confuses predators. In this manner mimics gain a survival advantage and leave more offspring carrying genes leading to mimetic phenotype. Some Heliconius species also show Mullerian mimicry in which two or more unrelated species are all toxic and together they form a very strongly reinforced warning signal to predators. A predator that ever tasted one species will never try another based on this unpleasant ordeal and all species collectively will gain survival advantage. Underlying genetical causes of Heliconius butterflies mimicry and speciation have been well studied and now are being investigated at genomic level.

One form of mimicry is to resemble a visually exaggerated predator to scare the predator away. Many fruit flies belonging to Tephriditae family have wing pigmentation patterns that resemble a jumping spider. Rhagoletis wallnut fly is one of them. Not all wing patterns could be a defensive mimic strategy and claims must be tested. On the other hand human vision may not be sufficient to detect color patterns reflected by transparent insect wings and need further exploration.

In addition to the picture wing fly, you can watch a female fruit fly (aka peacock fly; Xyphosia punctigera, family Tephritidae) from Japan semaphoring around on the leaves of mugwort (Artemisia indica var. maximowiczii, family Asteraceae) as if showing off the intricate pattern of the wings. The video was recorded late July in 2009.

One great tested example comes from metalmark moths of Costa Rica that mimic their jumping spider predator. Researchers Jadranka Rota and David Wagner tested four species of metalmark moths belonging to genus Brenthia and recorded their behavioral interactions inside a plastic arena. The predator deterrence role of the wing patters were clearly demonstrated. Males of jumping spiders are particularly territorial and defend their territories aggressively. If a moth can mimic and move like a predator this will confer a survival advantage. In the wild these moths display their wings on leaf tops. Behavioral trials using moths without wing patterns clearly show that jumping spiders are very effective visual predators. Metalmark moth wing patterns are quite sucessful in deceiving and repelling predatory jumping spiders:

Spider-mimic Metalmark Moths of Costa Rica from Nature Documentaries on Vimeo.

Perhaps some of the best documented examples of mimicry are from insect world. The following section from BBC’s “Life in the Undergrowth” presents two types of deceptive mimicry. In the first, Australian stick insect eggs look like a seed encased with elaiosome-like tissue. Ants are particularly fond of carrying seeds with elaiosomes which are rich in lipids and proteins. Once inside the nest the eggs are safe and ignored by ants probably because they change chemistry. The second example has a bit more complicated natural history involving blister beetles of California deserts. Blister beetle larvae deceive male digger bees by emitting sex pheromones and use them as carriers. When male digger bees try to copulate with a female bee the larvae hop onto females and get transported to her nest where they devour on pollen and also the larvae of the host bee.



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