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Spring 2012

Urban Jungle

The changing natural world at our doorsteps | Illustration and text by Patterson Clark      

June 19, 2012

Picture wing flies: Clowns of the outdoor cafe

Occasionally performing on bright, sunny surfaces, the picture wing fly at first glance looks and runs like a medium-size ant, but the insect appears to have a tiny gas mask for a head, and from its back rise two harlequin wings that slowly row the air.

When the fly finds a prominent spot to show off — such as on a stack of artificial sweetener packets — each of its two boldly patterned wings will move independently, delivering a miniature semaphore message for another picture wing fly to decipher.

The flies appear at many outdoor venues, so a cafe with planters is as good a place as any to perhaps catch an act. The fly will show no interest in your food, as it prefers the juices of decaying plants.

Rotting vegetation is also where the fly lays its eggs. Larvae feed for about a month, pupate for another couple of weeks and emerge as adults throughout the summer months. When the weather cools, late-season larvae slow their development, crawl deep into the humus and drift into quiescence for the winter. Next May, warm temperatures will inspire larvae to squirm to the surface, undergo metamorphosis and emerge for another round of summer antics.

SOURCES: Journal of Insect Behavior, Annals of the Entomological Society of America, University of Florida Institute of Food and Agricultural Sciences

Picture Wing Fly, Delphinia picta

Delphinia picta

Like many other flies,
picture wing flies
sometimes "bubble," regurgitating a drop of of their meal and holding it in their mouthparts for a while before reingesting it. Flies that swallow solutions with a higher water content are more likely to bubble, leading entomologists to believe that bubbling evaporates water from the droplet, concentrating the liquid meal into a smaller, more digestible volume.