330 PERCY SLADEN TRUST EXPEDITION 



eye to eye) to close up to the base of the antennae: the front edge terminates in a 

 slightly curved line which covers one-third of the frontal breadth ; the side margins are 

 slightly concave. 



Note. When the specimen is shrivelled the shape of the frons etc. has a somewhat 

 different appearance: the central strip of the frons is more strongly chitinized than the 

 spaces between it and the eyes; on drying this central strip falls in and drags the side 

 strips down with it so that the frons appears to be deeply furrowed; the bottom of 

 the furrow being the central strip, the side strips now form roughly perpendicular 

 boundaries of the furrow. When this occurs the eye-margins no longer appear parallel 

 throughout. 



The face is yellow slightly dusted with silver, with two very shallow antennal fovese: 

 the mouth opening when viewed perpendicularly to its plane is trapezoidal in outline; 

 the upper lip is pale, the sides of the mouth edge are margined with a fine brown line ; 

 palpi and tongue reddish brown. 



Antennae reddish yellow with a brown slightly pubescent arista. 



Back of head black with a broad yellow margin all round; jowls very small. 



Thorax (PI. 16, fig. 3). Dorsum shining black with a somewhat irregular contour, 

 having a nick at the cross suture, and a slightly wavy and less sharply defined hind 

 margin. The black central part is bordered with bright yellow; pleura yellow with 

 a reddish linear spot just behind the cross suture and an elongated black spot on the same. 



Fig. 18. Ops glaberrima, n. sp., wing. 



Scutellurn in the form of a nearly equilateral triangle with rounded angles: very 

 flattened on the dorsum; a pair of short black converging terminal bristles; metanotum 

 shining black. 



Wings (Fig. 18): venation normal, the distal part of the fourth vein being much less 

 distinct than the other veins ; extreme base of costa blackish and slightly swollen. 



Halters with bright canary yellow knobs, stalks blackened beneath. 



Legs pale yellow including the tarsi, which have minute black claws. 



Abdomen. First and second segments reddish yellow, the latter with the usual two 

 tiny black spots on the extreme margin, sides paler. The third shining black including 

 the sides to the belly. Fourth yellowish with a broad black stripe interrupted in the 

 centre, the breadth of stripe and interruption varying somewhat in different specimens. 

 Fifth yellow with two elongate black basal side spots, the remainder being pale yellow. 



Size. 2 to 2^ mm. 



