Research Grade Species #1290: Asteromyia carbonifera
Wasps aren't the only creatures that create galls (see previous entry for why I started this way). After the strangely complex tale of the Oak Wart Gall, I figured a nice straightforward midge gall of goldenrod would be nice. Then I did the reading.
A gall midge is a fly (different from a wasp in many ways, but most obviously in having 2 wings instead of 4) that spends its youth in the tissue of a plant. Because goldenrods (Solidago sp.) are annual plants, that means no tricky and time-consuming alternating "agamal" and "sexual" life stages. In fact, in the case of Asteromyia carbonifera (no common name, but the scientific name translates to star-fly carbon-bringer--references to the aster family that goldenrod belongs to and I guess the dark circles of the mature galls) there are many generations in a single year.
Now, developing in a gall as a form of protection has its limitations. The main limitation comes in the form of parasitoid wasps that lay their own eggs in the gall so that the wasp grubs can feed on the midge maggots. It so happens that there is a fungus (Botryosphaeria dothidea) that can form cankers (hardened tissue bodies) on a very broad range of plants, including goldenrods. Wouldn't you know it, the mother A. carbonifera midge has been shown by researchers to carry spores of this fungus on its body, inoculating the gall with it, as she lays her eggs. The fungus thickens and hardens the walls of the gall, making it more difficult for the parasitoid wasp to access the delicious midge maggots inside.
I recall when I first noticed the eyelike spots of this gall on goldenrod, that I wondered "is this an arthropod gall, or a fungal canker?" Somehow I was not prepared for the answer, "both."
