[509] THE SPHEGOIDEA AND VESPOIDEA III 



with the types of the latter species in the collection of the American En- 

 tomological Society leads the writer to the conclusion that the northern 

 form is distinct, since in M. mixta the antennae and petiole are both 

 shorter, the posterior face of the middle segment is not depressed and 

 the smooth area at the base is lacking ; also the front of the head is 

 striato-punctate, which is not the case in the new form. 



VESPOIDEA. 

 Family POMPILIIXE. 



Arachnospila septentrionalis sp. nov. 



Female : Black ; first and second segments of abdomen sanguineous 

 except the extreme base of first segment and narrow apical margin of 

 second, which are black; head broader than thorax, smooth, with in- 

 distinct, widely separated punctures; vertex and front sparsely clothed 

 with long black hair, a greater abundance of the same on the cheeks ; 

 eyes separated from the mandibles by a narrow margin, converging 

 but little above, the space between them equal to one and one-half 

 times the length of the first joint of the flagellum ; space between hind 

 ocelli a little less than that between them and nearest eye-margin; 

 clypeus very slightly emarginate, almost truncate, the lateral anterior 

 angles rounded and the anterior border finely margined ; antennae 

 slender, nearly as long as head and thorax, first joint of flagellum 

 longer by one-fourth than the second ; pronotum angulate behind ; 

 scutellum flatly convex in the center, declivous at the sides ; middle 

 segment strongly rounded out, smooth, with a faint trace of a medial 

 groove; medial and posterior tibiae and tarsi with numerous spines 

 outwardly ; anterior tibiae and tarsi with a row of spines along outer 

 margin ; tarsi coarsely ciliated beneath ; inner spur of hind tibiae two- 

 thirds the length of the first tarsal joint; claws with a sharp median 

 tooth ; abdomen elongate-ovate, as long as the head and thorax ; 

 wings fuliginous; third submarginal narrowed about one-fourth on 

 upper margin, the third cubital nervure curved outwardly; second 

 submarginal of nearly the same shape and slightly smaller than the 

 third submarginal, the first cubital nervure curved toward the base of 

 the wing; first recurrent nervure received a little beyond the middle 

 of the second submarginal ; second recurrent received before the mid- 

 dle of the third submarginal cell. Length 8.5 to 9 mm. 



Two females, Kukak Bay, Alaska. Taken on the flowers of Hera- 

 cleum lanatum. 



Type. Cat. no. 5313, U. S. National Museum. 



