EXOPEOSOPA. 77 



37 (36) . Underside of the head densely pilose, the root of the antennae, 



epistoma, mouth, &c. being completely hidden Anastcechus, 0. S. 



38 (31). Three suhmarginal cells Pantarbes, O. S. 



39 (30) . First posterior cell open. 



40 (47). Two submarginal cells. 



41 (42) . Both basal cells of equal length Sparnopolius, Loew. 



42 (41). First basal cell longer than the second. 



43 (44). Third antennal joint not truncate at the tip Epibates, O. S.; 



Eclimus, Loew. 



44 (43). Third antennal joint flattened, truncate at the tip. 



45 (46). Proboscis short Paracosmus, O. S. 



46 (45) . Proboscis very long Phthiria, Meig. 



47 (40). Three submarginal cells. 



48 (49) . The rather narrow marginal cell very much expanded at the 



end Lordotus, Loew. 



49 (48) . The marginal cell only moderately expanded Ploas, Latr. 



50 (29) . Three posterior cells ; anal cell closed. 



51 (52). Proboscis much longer than the antennae; small, Bombylius- 



like pubescent insects Geron, Meig. 



52 (51). Proboscis shorter than the antennae; long, Ammophila-Uke } 



almost glabrous insects ; four basal segments of the abdomen 



very narrow Systropus, Wiedem. 



EXOPEOSOPA. 



Exoprosopa, Macquart, Dipt. Exot. ii. 1, p. 35 (1840). 

 Trinaria, Mulsant, Mem. Acad, de Lyon, 1852, p. 18. 



Under this name Macquart separated from the old genus Anthrax those species 

 which have three or four submarginal cells. As further characters he mentioned " a 

 more or less projecting, conical face ; antennae with an elongated, subulate third joint, 

 and with a distinct style, ordinarily half as long as that joint." He was aware of the 

 numerous structural modifications occurring in the genus, especially in the venation. 



Loew, Siidafr. Dipt. p. 223 (1860), pointed out that thus far the presence of three 

 submarginal cells is the only trustworthy character; he added to it the absence of 

 pulvilli (but this character is common to the majority of the 'Anthraeina') ; the other 

 characters mentioned by Macquart occur, says Loew, in most, but not in all, the species 

 of Exoprosopa, and are also found in some species of Anthrax. He mentions inci- 

 dentally that some species have a tooth at the base of the ungues, but takes no further 

 notice of this character, which, as will be shown below, I found quite useful for the 

 definition of the groups of the North- American Exoprosqpce. He rejects the genus 

 Litorhynchus, Macq., merely distinguished by a longer proboscis; neither does he 

 admit Argyrospila, Bond., in which, as will be shown below, I fully concur with him. 



Schiner (Fauna Austr. i. p. 54, 1862) did not do anything towards the closer defini- 



