28 Myron Harmon Szvenk 



1900. Anthidium (Dianthidium) parvum Cockerell, Ann. Mag. Nat. 



Hist., series 7, V, p. 413 (in part). 

 1904. Dianthidium ulkei Cockerell, Bull. Sou. California Acad. Set., 



Ill, p. 6. 

 1909. Dianthidium ulkei Cockerell, Entomological News, XX, p. 261, 



? c?. 



Abundant in the Pine Ridge of Sioux and Dawes counties, July 

 I to August 20, at flowers of H elianthiis petiolaris, Gutierresia 

 sarothrae, Carduus plattensis, Vernonia fasciculata, Cleome ser- 

 rulata and Monarda fistulosa. A series of fifty-three females 

 and twenty-four males is before the writer from Warbonnet and 

 Monroe canyons, Glen and Crawford. In the clay buttes about 

 Glen we found its resinous brood cells commonly in August, 1906, 

 and bred the bees from them. A study of the series shows con- 

 siderable variation, especially among the females, and in frequent 

 cases there is a marked tendency to approach quite closely the 

 maculations of D. parvum (Cresson). Typically and usually, 

 the outer faces of the tibiae are bright yellow, but sometimes the 

 black encroaches on the sides so as to reduce the yellow on the 

 first four tibiae to mere broad stripes, while the posterior pair 

 have large antero-median black areas, or, in the extreme of 

 blackening, are black with the bases yellow and sending a yellow 

 streak down the posterior face of the joint. Such specimens also 

 have the emarginations of the band on tergite i cutting through 

 and the spots on tergite 6 lacking, but as specimens of tdkei with 

 the typical amount of yellow on the legs may also have tergite i 

 three spotted and tergite 6 immaculate or with the spots much 

 reduced, these differences are clearly within the individual varia- 

 tion within the species. None of the specimens have the yellow 

 of the tibiae restricted to mere basal spots, as in parvum $, and 

 the clypeus always has lateral yellow spots or bands, while in 

 most specimens a yellow supraclypeal, vertical, postocellar or 

 pleural spot or a yellow stripe on the anterior femora betray the 

 insect at once as idkei, all these markings being lacking in parvum. 

 The male of idkei differs at once from parvum (^ in the quite 

 diflferent pygidium, parvum having distinct notches at the sides of 

 the median apical tooth which are lacking in ulkei. We have 



28 



