SIMULIUM. 187 



tlie 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. Sainbon's investigations have placed its origin with 

 Simidium beyond a shadow of doubt. 



Siniidiwn has a synonym in Mdusina, Mg., 1800, but the latter 

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

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

 changed. 



Table of Siiecics. 



1. Thorax black, at most with a dull reddish 



brown tintre occasionally 2. 



Thorax distinctly reddish brown, with 

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



2. Thorax with grey shoulder spots and a 



wide greyish band on posterior margin, grisescens, Brim., 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 larce as the tibire * mefatarsale, Brun., p. 189. 



Hind metatarsus not so conspicuously in- 

 crassated, distinctly less in size than 

 the tibiae * 5. 



5. Antenna) wholly black. Length 2i mm. yriseifrons, Brun., p. 190. 

 Antennae reddish yellow at base. Length 



1^ mm riifibasis, Brun., p. 190. 



6. Abdomen with normal short very bright 



yellow hair 7. 



Abdomen with distinctly longer, shaggy 

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



7. Abdomen with at least the first two seg- 



ments distinctly yellowish or brownish 

 yellow ; often several segments so 



coloured iyidkiim, Beclier, p. 191 . 



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



lo6. Sinmlium rufithorax, Brun. 



Simuliian rufithorax, Brunetti, Eec. Ind. JMus. iv, p. 282 (1911). 



(S $ . Head : eyes dull red, the upper facets in tlie male very 

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

 the eyes being absolutely contiguous from the extreme vertex to 

 the antennae. In the female, the facets uniformly small, the frons 



* This is probably a sexual character, but no better one offers it.self, and the 

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



