440 



NEMESTRINID^ 



V. NEMESTRINIDiE. 



Orthorrhaphous brachycerous eremochsetous flies of rather large size, 

 distinguished by their peculiar venation. 



FiQ. 250.— Nemestrina Perezii $ . x 3J 



Head broad and short, but often not quite so broad as the thorax, set close 

 against the thorax so that there is no visible neck, nearly always clothed with dense 

 soft equal pubescence but sometimes with a strong tuft on the upjjer part of the 

 frons, or occasionally the pubescence may be rather slight, and the cephalic bi'istles 

 are entirely absent. Face small, more or less roundedly produced, separated 

 from the frons by a sharply marked deep suture, usually densely and equally 

 pubescent but occasionally bare, and never with any approach to a face-beard as in 

 the Asilidce. Frons and vertex flush with the eyes or slightly raised ; frons some- 

 times wide in both sexes, or contracted in the male, or comparatively narrow in the 

 female and completely closed by the eyes in the male ; Avhen the frons is very broad 

 the ocellar triangle is very large and the three ocelli are placed widely apart, but 

 when the eyes are touching the ocellar triangle is necessarily small and the ocelli are 

 closer together, wdiile in Colax they appear to be altogether absent. Proboscis often 

 very long, thin, and porrect (in Nemestrina lonr/irostris about four times as long- 

 as the whole fly), or long without being porrect (being bent down), or quite short and 

 thick {Hermoneura), and when elongate the sucker-flaps are usually small ; palpi 

 one- two- or three-jointed, often indistinct, but sometimes rather long and 

 very thin and upturned, or occasionally a little clavate. Eyes usually widely 

 separated on the frons in both sexes, but sometimes approximated or even closely 

 touching for a long distance in the male and then only narrowly separated in the 

 female, usually bare but in some genera with very dense and even long pubescence ; 

 facets usiially all equal, but I think that the front facets are sometimes a little 

 enlarged in the male. Antennae very widely separated at the base, small, and 

 inconspicuous unless the thin arista-like style be long ; two basal joints bearing stiff 

 hairs ; tliird joint almost as short as the others but more pointed, or more elongate, 

 and bearing a terminal stout or thin bristle-like usually jointed style which is longer 

 than the antennae and is occasionally tufted at its end. 



Thorax rather quadrate with the humeri inconspicuous, absolutely witliout bristles 

 or bristly hairs but almost always bearing dense fairly equal pubescence all over 

 the disc, the pleurpe, and the scutellum ; even the usual patches of stiffer hairs about 

 the postalar calli are absent, but sometimes the pleur<B bear longer tufts of hairs 

 near the back of the mesopleuree and on the upper part of the metapleurse behind 



