1917] The Ottawa Naturalist 1 3 



LITTLE KNOWN MIDGE GALLS OF 

 CERTAIN COMPOSITES. 



By E. P. Felt, Albany, N.Y. 



The writer published in 1911* a tabulation of American Midge 

 Galls and since then a number of new ones have been discovered on 

 plants which are likely hosts of additional species. It is the purpose 

 of these notes to call attention to some interesting analogies and to 

 point out promising lines of investigation. 



The occurernce on the gum plant or tarweed, Grindelia, and on 

 Gutierrezia, of the typical blackened, carbonaceous tissue so conspicu- 

 ous in the oval black blister galls of the narrow-leaved goldenrod, is 

 most interesting, especially as all three are produced by midges be- 

 longing to the genus Aster omyia. The first is the work of Aster omyia 

 grindeliae Felt, the second of A. gutierreziae Ckll., and the third of the 

 much better known A. carbonifera Felt. The gall of A. gutierreziae 

 Felt differs from those of the other two species, in that it consists of 

 slight enlargements of the slender stems instead of a development upon 

 the leaf. Both Grindelia and Gutierrezia are known to support bud 

 or flower-inhabiting species of Rhopalomyia. Ericameria also has its 

 bud inhabitant, Rhopalomyia ericameriae Felt, which produces a 

 small rosette bud gall, really aborted branchlets. It is very probable 

 that the related and rather common Sideranthus supports one or more 

 gall midges. 



The various wormwoods or sage-brush of the western plains, 

 Artemisias, support an interesting and presumably only partly known 

 fauna. Two genera, Diarthronomyia and Rhopalomyia find very 

 acceptable conditions on these plants, particularly the former, a genus 

 which appears to confine itself largely to Artemisia and the related 

 Chrysanthemum. In order to facilitate the discovery of new species 

 on Artemisia, a tabulation of the known galls, including those of 

 associated forms, is given below. 



Insect Galls on Wormwood or Sage-brush x\rtemisia. 

 artemisia californica. 



Irregular, lobulate, woolly masses, apparently arising from lateral 

 buds and frequently confluent, the individual galls with a diameter of 

 about 4 mm. Diarthronomyia floccosa Felt 



Subconical, thin-walled, obliquely-set, brownish or reddish leaf 

 galls with a length of 1.5 mm., and a diameter of .5 mm. 



Diarthronomyia calif ornica Felt 



*Econon. Ent. Journ. 4:451-75. 



