no. 1834. 



NEW SPECIES OF STREPSIPTERA— PIERCE. 



493 



be a matter of considerable difficulty to secure a satisfactory arrange- 

 ment of the species. The females of Stylops show also many small 

 groups, and it is probable that when we know the males we will be 

 able to more definitely arrange them. It is, however, of interest to 

 note the coordination of the parasite and host classifications. Pter- 

 andrena asteris and P. solidaginis are grouped together, and so may 

 their parasites Stylops asteridis and S. swenki be grouped. The same 

 *s true of Andrena solidula and A. vicina and their parasites S. 

 solidulse and S. vicinse; of A. muUiplicata and A. nivalis and their 

 parasites S. multiplicatse and S. grsenicheri; of A. sparsipilosa and 

 A. subcandida and their parasites S. sparsipilosse and S. subcandidse. 



In the following table the species known to the writer are arranged 

 according to their relative forms as nearly as is possible. 



The first column of figures represents the ratio of the breadth of 

 the cephalothorax between the spiracles to the distance between the 

 mandibles; the second represents the ratio of the breadth of the head 

 to the distance between the mandibles; the third the ratio of the 

 breadth between the spiracles to the breadth of the head; the fourth 

 the ratio of the breadth between the spiracles to the distance from 

 spiracles to apex. 



Stylops species. 



Andrena species. 



Breadth to 

 length 



advarians 



harlfordensis . 



asteridis 



swenki 



hippotes 



bipunctatx... 



solidulx 



vicinse 



bruneri 



vierecki 



salicifloris 



polemonii 



multiplicatx. 



grxnkncri 



craivfordi 



cressoni 



sparsipilosse. 

 subcandidse . . 



nubeculx 



cornii 



calif arnica . . . 



nudx 



imitatrix 



claytonix 



nasoni 



andrenoides . , 

 mandibulars 

 oklahomx 



advarians 



harlfordensis. 



asteris 



solidaginis... 



hippotes 



bipunctata. . . 



solidula 



vicina 



illinoicnsis... 



texana 



salicifloris.. . 

 polemonii. .. 

 mvltiplicala . 



nivalis 



craivfordi 



cressoni 



sparsipilosa . 

 subcandida. . 



nubecula 



commoda 



subtilis 



nuda 



imitatrix 



claytonix 



nasoni 



andrenoides. . 

 mandibulars 

 flavoclypeata. 



1.41 

 1.40 

 1.35 

 1.65 

 1.77 

 1.37 

 1.32 

 1.40 

 1.79 

 1.50 

 1.42 

 1.32 

 1.52 

 1.50 

 1.55 

 1.53 

 1.53 

 1.58 

 1.57 

 1.34-1.35 

 1.51 

 1.34 

 1.55 

 1.49 

 1.45 

 1.34 

 1.51 

 1.43 



STYLOPS ANDRENOIDES, new species. 



Host. — Andrena andrenoides Cresson (det. Robertson), Carlinville, 

 Illinois. Described from one female collected by Charles Robertson. 



Female. — Length of cephalothorax 0.69 mm., breadth at spiracles 

 0.69 mm., breadth at base of head 0.39 mm., distance between 



