a Genus of Dipterous Insects. 287 



There are other peculiarities of structure, however, in the genus Diopsis 

 which contribute to its interest. Of these, the 4 or 6 spines which arm tlie 

 sides of the thorax and the extremity of tlie scutellum are remarkable. I am 

 aware of only one Muscideous insect resembling it in this respect, the Tetanoceru 

 bispinosa of Wiedemann, which has only two spines on the scutellum. Latreille 

 has, however, named an entire Dipterous group {Stratiomidw, &c.), from their 

 possessing similar scutellar spines, Notacantha ; but in none of these are the 

 sides of the thorax spined*. So also the two spines which arm the lower 

 sides of the face, and those placed at the extremity of the four posterior femora, 

 are exclusively confined to this genus, whilst the raptorial structure of the 

 fore legs is not amongst its least interesting characters. 



Respecting the characters of this genus the most detailed descriptions 

 hitherto given are those of Fabricius, Latreille, and Dalman, upon which, 

 however, a very careful investigation of the Diopsis Si/J(esii has rendered a 

 few observations necessary. Thus, Dalman describes the antknn^ as " vix 

 visibiliter triarticulatse — articulo tertio subovato — seta terminato ;" whilst La- 

 treille correctly describes them as " conipressse articulis tribus, 1 mo, minimo ; 

 2do, cyathiformi ; 3tio, suborbiculato ;" incorrectly adding, " ad basin seti- 

 gero," — the seta being inserted on the upper margin of tlie third joint near its 

 extremity. As to the trophi, the descriptions of Fabricius and Latreille do 

 not coincide, and Dalman was unable to examine their structure so as to 

 clear up the differences. Fabricius says, " Os baud prominens, proboscide, 

 haustello palpisque. Proboscis magna, membranacea, geniculata, retractilis : 

 stipite brcvi, cylindrico, capitulo carnoso, bilabiato : laciniis sequalibus, con- 

 niventibus. Ilaustellum absque vagina, seta unica, cornea, setacea, acuta, in 

 canalem dorsalem proboscidis recondenda. Palpi duo, elongati, conici, ad 

 basin setoe inserti :" whilst Latreille merely observes, " Proboscis Muscarum. 

 Palpi breves, cylindrici, subacuminati." In the Diopsis Si/kesii, however, the 

 mouth exhibits a more perfect organization than has hitherto been noticed in 

 any of the great second division of the Athericerous Diptera to which it be- 

 longs, closely resembling, in fact, the structure of Latreille's first division of tlie 



* I have more recently noticed in the collection at the East India House a species of Sargus, brought 

 from Java by Dr. Horsfield, the thorax of which possesses lateral as well as scutellar spines. ITie same 

 also occurs in the genus Clilellaria. 



