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Spring 2010

Urban Jungle

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


March 30, 2010

Blowfly emergence

In early spring, blowflies emerge from the ground's top two inches of soil, where last fall's late-season maggots overwintered.

Bigger than a housefly, these "bottle flies" are often seen basking on sunny outdoor walls. A fly will sponge up flower nectar, such as from the spicebush blossoms shown at left, but if its antennae catch the scent of decaying flesh -- as far as 10 miles away the insect will launch a relentless search for it.

Female blowflies will lay eggs on dung or rotting vegetation, but fresh carrion is their preferred breeding site. The tiny eggs are deposited in "rice ball" clumps of 200 that quickly hatch into maggots, which grow, molt, pupate and emerge as adults within two or three weeks.

Blowfly maggots are so effective at devouring necrotic tissue that they are sometimes used by surgeons to clean out wounds and stimulate healing. Used for centuries, maggot therapy has been readopted by numerous wound-treatment centers after the practice fell out of favor in the mid-1940s.

SOURCES: University of California at Riverside; University of California at Irvine