I’m in Burlington, Vermont for the week, and I’ve been taking advantage of the relative abundance of hackberry (Celtis occidentalis) trees here in the Champlain Valley to look for the galls of Celticecis midges. Gall midge specialist Dr. Raymond J. Gagné is finishing up a paper on these hackberry-specific midges and their galls, in which he is describing a number of new species and revising some old ones, and I’m doing my best to help him out by collecting galls and sending them to him. Here near the northern edge of hackberry’s range, the galls are scarce–after visiting several different spots where I know I’ve found hackberry before, I finally found the first ones today:
Celticecis spiniformis seems to be the most common species, and I think it may be the only one that occurs this far north*. In Tennessee and Mississippi, I’ve found several different types of galls just standing in one spot and examining the leaves of a single tree. I’m fascinated by the diversity of shapes in these galls, and can’t imagine what purpose they might serve, other than giving naturalists a handy way to tell all the different species apart. As far as I know, all Celticecis galls form in the spring, with a single larva developing inside each one. When the larva is mature, its gall drops to the ground. Adults emerge from the fallen galls in the spring, mate, and then females fly to hackberry trees to lay eggs. Below are some more examples of Celticecis galls that I’ve already sent to Dr. Gagné. Not all of them have names yet; when his paper is published I’ll post an update with more information about them. If you are interested in hunting for these galls to collect and send him, just put the whole leaves in ziplock-type bags, send me an email, and I’ll put you in touch with him. Note that he is not interested in the hackberry psyllid galls (the three most common species are shown here), which are not detachable like the midge galls.
Two from Kentucky:
And the rest are all from a single sapling in Nashville, Tennessee:
* Upon receiving these galls, Dr. Gagné told me that they were the first hackberry midge galls of any kind that he had seen from New England. The closest previous records were from Ithaca, New York, and yes, only C. spiniformis has been found there.