SIMULIUM. 187 



the fly synchronizing with or closely following upon the climatic, 

 variations from one season to another. The disease is non- 

 contagious, and the parasite has not been actually discovered. 

 It was previously thought to have been caused by eating diseased 

 maize, but Dr. Sambon's investigations have placed its origin with 

 Simulium beyond a shadow of doubt. 



Simulium has a synonym in Melusina, Mg., 1800, but the latter 

 name is unorthodox, no species being allotted to it ; moreover, 

 Lntreille's name has been so loug in use that it ought not to be 

 changed. 



Table of Species. 



1. Thorax black, at most with a dull reddish 



brown tinge occasionally 2. 



Thorax distinctly reddish brown, with 

 short yellow hair ritfithorax, Bruu., p. 187. 



2. Thorax with grey shoulder spots and a 



wide greyish band on posterior margin, yrisescens, Brun., p. 188. 

 Thorax without either grey shoulder spots 

 or posterior bands 3. 



3. Abdomen destitute of any sign of yellow 



hair ." 4. 



Abdomen with short bright yellow hair 

 or with long rather shaggy brownish 

 yellow hair 6. 



4. Hind metatarsus much incrassated, nearly 



as long and laree as the tibiae * metatarsale, Brun., p. 189. 



Hind metatarsus not so conspicuously in- 

 crassated, distinctly less in size than 

 the tibiae * 5. 



5. Antennae wholly black. Length 2^ mm. griseifrons, Brun., p. 190. 

 Antennas reddish yellow at base. Length 



1J mm rujibasis, Brun., p. 190. 



6. Abdomen with normal short very bright 



yellow hair 7. 



Abdomen with distinctly longer, shaggy 

 brownish yellow hair senile, Brun., p. 191. 



7. Abdomen with at least the first two seg- 



ments distinctly yellowish or brownish 

 yellow ; often several segments so 



coloured indicum, Becher, p. 191. 



Abdomen all black aitreohirtum, Brun., p. 194. 



136. Simulium rufithorax, Brim. 



Simulium rufithorax, Brunetti, Rec. Ind. Mus. iv, p. 282 (1911). 



<3 $ . Head : eyes dull red, the upper facets in the male very 

 large, the lower ones small, sharply demarcated from each other, 

 the eyes being absolutely contiguous from the extreme vertex to 

 the antenna?. In the female, the facets uniformly small, the frons 



* This is probably a sexual character, but no better one offers itself, and the 

 two forms may possibly be male and female of the same species. 



