GUESTS AND PARASITES OF HALICTUS. 19 



flattened, oval in cross-section. No ventral sclerites are present. Each 

 segment is margined behind with small bristles and is hairy elsewhere as 

 is the entire body. Glandular opening of the fifth segment l in the shape of 

 an arcuate slit. External genital organs of the usual form. Legs rather 

 stout, the tibiae with two apical spurs. 



Length, 0.75 mm. Testaceous, head and thorax darker above, espe- 

 cially directly about the ocelli. Abdominal plates dark fuscous, the mem- 

 branous parts almost white, with a small fuscous spot at the insertion of 

 each hair. 



This form is a typical representative of the Stethopathinae and 

 strange to say, it approaches more nearly to the East Indian 

 Stethopathus occllatns Wand, than to any of the species that have 

 hitherto been discovered in America. Indeed, it is here regarded 

 as congeneric with the former, although the two species are from 

 such widely separated regions of the earth. 2 It may be neces- 

 sary later to separate these two forms, but at the present state of 

 our knowledge of this group it does not seem advisable. The 

 American species resembles 5. ocellatits Wand, in possessing 

 ocelli, being utterly destitute of wings and halteres, and in having 

 a similarly shaped head and abdomen. But differences in form 

 are also evident : the thorax is only twice as wide as long, in- 

 stead of three times as in ocellatits, the palpi are clavate, not 

 spindle-shaped, and the chaetotaxy is somewhat different, although 

 conforming to the same general type. Although its habitus seems 

 to be quite different from that of the genus dEnigmatias Meinert 

 (which it may be recalled, has just been discovered in Arizona, 3 

 a locality quite distant from its home in Denmark), yet this spe- 

 cies may possibly prove to be a close relative. 



A point perhaps of minor importance, but nevertheless inter- 

 esting as bearing upon its systematic position, is the fact that the 



1 In previous papers the gland opening has been referred to the fourth segment of 

 the abdomen, but the very short first segment in the present species leads us to believe 

 that this sclerite is concealed in the other American species and that there, too, the 

 gland really opens on the fifth segment. 



2 Many cases might be mentioned of monotypical or very small genera of insects, 

 which have an inexplicably wide discontinuous distribution. Amphizoa with two- 

 species, one in western North America and another in Tibet ; Syntelia, which is rep- 

 resented by two species, occurs in Mexico and eastern Asia ; and the water-beetle, 

 Pelobius, occurring in western Europe, Tibet and Australia. For further references 

 to the close approximation in certain details of the faunre of eastern North America 

 and Asia, see C. C. Adams, " The Southeastern United States as a Center of Geo- 

 graphical Distribution of Flora and Fauna," BIOL. BULL., Vol. III., pp. 115, et seq. 



3 1). W. Coquillett, Can. Ent., 1903, p. 20. 



