Salix (willow) stem galls

Swellings in willow stems could be made by Euura spp. sawflies (of which there are more than 25 in North America) or by gall midges (and smaller ones could be made by agromyzid flies too). In many cases, to be sure which is responsible, it is necessary to either collect some and see what emerges, or cut them open (you can do this with old abandoned ones if you don't want to kill the inhabitants): sawfly galls would have frass and empty cocoons inside; midge galls would not. Once we have some images of galls that have been identified in this way, it may be possible to identify some of the galls in this section.

To the above note by Charley Eiseman, Bob Carlson adds: "Another maker of stem galls on willow is Agrilus criddlei Frost [Buprestidae]. I have reared it from willow galls in Benzie County, Michigan." The adults emerge in late May and in June.