MTCHODON. 119 



Genus 25. MICRODON, Me i yen (1303). 



In the case of this genus the collection includes very many 

 interesting species, the majority of which are strikingly coloured, 

 while some appear to mimic various species of Hymenoptera. The 

 differences in structural characters are so pronounced tliat separation 

 into minor genera seems to be necessary ; this, however, is not easy, 

 because the shape of antennae is very variable and shows gradual 

 transition to the extreme forms; the scutellum also gradually 

 passes from the armed to the unarmed form. 



Of the generally accepted genera, Ctratopkya, Myxogaster, and 

 Rkopalosyrphus are exclusively American, and therefore need not 

 be considered here. In the collection, however, there is a mutilated 

 specimen from the Cape which closely resembles Myxoyaster or 

 Jtkopalosyrphu*, but has two small spines on the scutellum ; 

 Dr. J. C. H. de Meijere, again, has described three Oriental species 

 ( cespifonnix, indicus, and ody nereides), which exhibit the characters 

 of the genera mentioned, while in each case the scutellum is 

 unarmed. 



The recently described genus Paramicrodon, de Meijere, 1913, 

 which occurs in Xew Guinea, has short antennae and an unarmed 

 scutellum, and is distinguished by the absence of a stump on the 

 third vein. 



Of the generic names relegated to synonymy, Chymopkila 

 proved to have been applied to a Alteration with the head of a 

 Conops glued upon it ; Dimertupit was bestowed upon a true 

 North- American Microdoii not far removed from the European 

 forms, but with an unarmed scutellum ; 3fnopkila is merelv a 

 no men nil J um, which also applies to a North- American species of 

 true Mi c rod on, with bilobed scutellum ; Tfbritte* was bestowed 

 upon a Neotropical species, and, although its characters were not 

 clearly defined, it was possibly meant to include South- American 

 forms with an unarmed scutellum; Omegasyrphus also includes 

 American forms with narrow abdomens, the second segment of 

 which exhibits a very peculiar sculpture. 



As stated above, the Ethiopian forms before me exhibit a 

 great many structural variations, the existence of which renders it 

 necessary to institute new genera ; for the present, however, it seems 

 better to divide the species in question into anonymous groups, 

 since some of the names mentioned above can perhaps be applied 

 to them. I have introduced only two new generic names for two 

 very striking forms, one of which is allied to Eu merits and has 

 been described above. 



The following is a table for the distinction of the Ethiopian 

 groups of the genus ALicrodon, s. 1., with the addition of the two 

 new genera : 



1 (14) Middle cross-vein situate on the basal third of 

 the discal cell; third longitudinal vein pro- 

 vided with the usual peculiar stump in the 

 subapical cell ; a distinct cross-vein uniting 



