N. erigerontis [induces] a large, more or less soft, pithy gall near the base of or midway up the stem [of Erigeron canadensis. The gall] appears in summer and is variable in size but usually many centimeters long and twice the normal diameter of the stem; it is polythalamous and can contain as many as 50 larvae. ,,, Adults ... emerge ... in both summer and spring.

[Here is the full text of the comparison between Neolasioptera eregeroni and N erigerontis from which the briefer quote above was taken]
Larva in stem swellings, either rough and usually to one side of stem or smooth, tapered.
Two different kinds of stem galls occur on this host [Conyza canadensis]: a large, more or less soft, pithy gall near the base of or midway up the stem and a smaller, harder gall on branches of the inflorescence. The first kind appears in summer and is variable in size but usually many centimeters long and twice the normal diameter of the stem; it is polythalamous and can contain as many as 50 larvae. The other appears much later, in fall, is monothalamous and usually about 10 mm long by 5 mm in diameter. Adults from at least the large galls emerge from the hosts in both summer and spring. Larvae from the two kinds of gall show a few minor differences, but adults have not been reared from the inflorescence gall. If the two galls are shown to be made by two separate species, Brodie's name, N eregeroni, would be availble for the inflorescnce gall. Brodie wrote that some larvae escaped from the galls, which is not known in Neolasioptera, but the adults he reared do belong to Neolasioptera.

Host: Conyza canadensis

Disrt: MA to Ontario, south to MD, and NE and CA

- Raymond J. Gagne: (1989) The plant-feeding gall midges of North America^©