6. STRATIOMYS 149 



TaUe of Species. 



1 (4) Eyes of both sexes bare, and those of the female with a con- 



spicuous yellow postocular collar. 



Tibiae and belly mainly yellow, the latter with small black bands 

 or transverse spots. 



2 (3) Abdominal yellow markings composed of a pair of large basal 



spots followed by pairs of almost similar but less triangular 

 spots. 1 chamceleon. 



3 (2) Abdominal yellow markings composed of a pair of large basal 



spots followed by entire narrow bands or pairs of linear spots. 



2 potamida. 



4 (1) Eyes (of at least the male) hairy, and those of the female without 



any yellow postocular collar. 



Tibiae and belly mainly black, the latter with pale bands. 



5 (6) Abdominal pale spots rather small but distinct. Eyes of the 



female bare. 3 furcata. 



6 (5) Abdomen practically without pale spots. Eyes of the female 



hairy. 4 longicornis. 



Unusually pubescent species. 



1. S. chamseleon Linne. Eyes bare, in the female with an encircling 

 yellow band. Abdomen with three pairs of spots and the tip yellow ; belly 

 yellow, with small black spots and lines. 



A large well-marked handsome fly. 



S . Head moderately large. Face and frons forming an equilateral triangle, all 

 black except for two obscurely whitish yellow stripes low down on the sides 

 of the face close against the eyes ; face rather densely clothed with moderately 

 long greyish pubescence which is equal all over, and which extends on the 

 under part and on to all the back part of the head against the mouth, but 

 not on to the distinctly inflated lower half of the back of the head ; this 

 lower part of the back of the head is dull blackish and bears on its lower part 

 a short pale brown very decumbent pubescence which slopes forwards, and 

 just higher up there is a rather longer glistening white pubescence which 

 mainly slopes downwards, while quite at the back of the head right away 

 from the eyes there is some long greyish white yjubescence ; the upper half 

 of the postocular margin has only a very narrow blackish rim on which there 

 is a very minute black pubescence ; vertex black, shining, bare and corrugated 

 about the ocelli, but bearing a number of moderately short black hairs behind 

 the ocelli; the vertex at its widest part is less than one-twelfth the width 

 of the head but narrows forwards soon after the ocelli, and thence forward 

 the eyes are only slightly separated for nearly a third the distance between 

 the occiput and the antennae, and all along this space there is a line of 

 moderately long rather dense greyish black pubescence which ceases at the 

 commencement of the frontal triangle ; the frontal triangle has a middle 

 furrow which diverges a little before the antennae, and the furrow and this 

 enclosed space are bare and shining black, but the corrugated sides are rather 

 dull and bear a similar blackish grey (or at the top angle and the sides grey) 

 pubescence which extends slightly round the base of the antennae. Proboscis 

 blackish brown, with scattered brownish yellow hairs ; palpi inconspicuous, 

 blackish. Eyes occupying almost all the head, shining black and bare ; 

 facets all about equal. Antennae black, but the tip of the second joint 

 rather chestnut ; the shining basal joint of each antenna stands out straight 



