April 30, 2010
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A few months back I did a post on a common sight in wintry fields: round galls on the slender stems of goldenrod. In open areas, goldenrod galls are rarely left undamaged; birds such as woodpeckers and chickadees are quick to locate these highly conspicuous snack dispensers during the colder months.
On a walk this week I found a large, open, grassy field whose autumn vegetation appeared to have been rapidly and thoroughly flattened, perhaps by strong winds or a sudden blanket of heavy wet snow. The brown, dry remnants of last year’s growth formed a dense mat on the ground. Amid the grasses and burst milkweed pods were numerous goldenrod stalks, many of which sported fly galls. Interestingly, it would appear that their horizontality protected them from the sharp beaks of hungry birds; almost every gall I inspected was intact. Which meant: it was time for a magic trick.
I picked a stem with a nice pair of galls…my pocket knife came out of hiding…a lichen-covered rock became a cutting board…I carefully slid the blade halfway through the fleshy orb…and pried…
Fly larva! Only one, though; the occupant of the gall on the left had met its end some time ago, but the one of the right – wiggling vigorously!