Sept., i9i6.] Felt: New Western Gall Midges. 193 



concolorous swelling with a length about 2 mm., usually at a distinct 

 angle to the surface of the plant tissues, and frequently causing large, 

 confluent swellings of the stem, leaf or flower head of Chrysanthe- 

 mum hypogaea H. Lw. 



aa. IS or 16 antennal segments. 



b. Antennal segments of the female subsessile, the fifth with a stem one- 

 fifth the length of the cylindrical basal enlargement, the fifth of the 

 male with a stem three-fourths the length of the basal enlargement. 

 Reared from an oval, thin-walled, pubescent cell with a length about 

 I mm. and attached at an oblique angle to the vuider side of the leaf 

 or from flower buds of Artemisia heterophylla or a vertical, oval leaf 



gall on A. tridentata occidentalis n. sp. 



aaa. 14 antennal segments. 



b. Antennal segments of the female sessile, the fifth with a length twice 

 its diameter, the fifth antennal segment of the male with a stem 

 three-fourths the length of the basal enlargement ; circumfili not 

 greatly produced. Reared from a brownish or reddish subconical, 

 thin-walled cell with a length of 1.5 mm., a diameter of .5 mm. and 

 protruding at an oblique angle from the tissues of Artemisia cali- 

 fornica calif ornica Felt. 



bb. Antennal segments of the female sessile, the fifth with a length four 

 times its diameter, the circumfili greatly produced and frequently ex- 

 tending to or beyond the base of the next segment. Reared from ir- 

 regular, lobulate, woolly masses, apparently lateral bud galls which 

 are frequently confluent ; individual galls with a diameter of 4 mm., 

 on Artemisia californica floccosa n. sp. 



Diarthronomyia artemisise Felt. 



A series of midges were reared by Mr. P. H. Timberlake in May 

 and Jnne, 191 5, from variable, globose, leaf bud and rosette galls on 

 Artemisia tridentata, and also from a bladdery leaf gall found upon 

 the same plant and collected near Salt Lake City, Utah. The leaf 

 bud galls presented a marked variation in pubescence, the smaller 

 ones being naturally more pubescent, while the larger ones, presum- 

 ably because of the greater expansion of the normal stirface of the 

 plant, are decidedly less pubescent. The larger ones, according to 

 Mr. Timberlake, are polythalamous, the others monothalamous. The 

 bladdery leaf galls are notably softer than the others and less pubes- 

 cent, as in the case of the larger leaf bud galls. The interior of these 

 deformities is filled with loose, spongy matter composed of finely 

 crinkled filaments surrounding one or more larval cells. 



Exuvium. — Length 2 mm. Stout, the head, mesonotum, antennal and 

 wing cases a variable reddish brown, the anterior horns small, the antennal 



