ACROCERID FLIES — SCHLINGER 361 



downward, while the first two segments project straight forward; the 

 antennal tubercle is large, nearly half as high as eye height, and is 

 placed on the head so that its ventral siu-face is at or above the mideye 

 height level (figs. l,b, 3,e); the third antennal segment is longer ard 

 more laterally compressed than in the female, and the fii'st segment 

 is longer along its dorsal than its ventral surface. 



Another character such as the longer abdomen of the male might 

 also be noted and, if ecuadorensis, new species, is an indication, the 

 color and maculation of the sexes may differ among the species of 

 Pialea; however, this is more likel}^ a specific rather than a generic 

 character. One important and rather unique structure of the anten- 

 nae, which is common to both sexes, is the whole or partial fusion of 

 the first segment of each antenna into a common basal segment (figs. 

 3,c,f,h,i, 4:J). This latter feature is apparentl}^ shared by Stenopialea 

 beckeri as deduced from the original description. Differences in 

 antennal structure are frequently found between the sexes of species 

 in the brachycerous Diptera, but I have been unable to find mention 

 of any species exhibiting the significant difference of antennal insertion 

 as described above. 



System ATics 



The genus Pialea is in the subfamily Panopinae, and I believe it to 

 be one of the more primitive genera of Acroceridae. It is more 

 closely related to the still more primitive genus Stenopialea Speiser 

 from South Africa tlian to its nearest South American relatives, 

 Pialeoidea Westwood and Ocnaea Erichson. This would certainly 

 suggest a definite relationship of the two faunas and a wider dis- 

 tribution of Pialea or Stenopialea, or both, sometime in the past. 



It seems possible that lutescens Westwood and antiqua, new species, 

 belong in a distinct genus, tending to fill the gap between Pialea and 

 Stenopialea. However, for lack of sufficient material, these two species 

 have been included in Pialea. Thus, the genus is redescribed below 

 in its widest sense, and, should it be necessary to narrow its limits in 

 the future, only three of tlie five known species — cap.itella, new species; 

 ecuadorensis, new species; and lomata Erichson — would be included in 

 typical Pialea. 



Genus Pialea Erichson 



Pialea Erichson, 1840, pp. 160-lGl, pi. 1, figs. 9, (9)p. 



Genotype: Pialea lomata Erichson (type by monot^q^y). 



Head: Extremely small compared to thorax; eyes pilose, in lateral 

 view covering anterior one-third to one-half of head capsule, weU 

 separated above and below antennae except in P. capitella (fig. l,c); 

 frontal region either with tubercle or somewhat raised; ocellar tubercle 



