a Genus of Dipterous Insects. 291 



eludes it from his " familia Jchiidarlum" probably on account of the form 

 and position of its antennae. Latreille also, in tlie second edition of the Regne 

 Animal, removes it from Jchias, and places it amongst his Carpomyza;, im- 

 mediately after Calobata, and before Cephalia, Sepsis, Ortalis, &c. With these 

 genera, indeed, it appears the most nearly allied, not only in the elongate form 

 of the body, but also in the maculation of the wings. The structure of the 

 mouth, however, in Diopsis, previously described, seems to indicate the want 

 of a decided affinity with these groups. 



Hitherto no facts respecting the habits of this genus have been published. 

 Dalman, evidently speaking from information supplied to him by Afzelius, 

 states that the latter found his specimens merely by accident in the windows 

 of houses. He has, however, made two observations, which are sufficient of 

 themselves to prove him to have been a first-rate entomologist, rendering 

 our regret at his loss the more painful: "Insectorum oculos valde promi- 

 nentes semper fere vitam super sabula vel ad ripas indicare, ut coUigere licet 

 ex Cicindela, Elaphro, Omophrone, Steno, inter Coleoptera ; Salda, Alydo inter 

 Hemiptera. Ceterum oculorum prominentia prsesertim insectis rapacibus 

 videtur esse propria, et adaptata ad istum vivendi modum, ut in jam supra re- 

 censitis et in Libellulinis, Hemerobio et aliis ;" adding, however, " Oris tamen 

 ratio in Diopsi a prseda capienda aliena videtur." The statement, however, 

 which Colonel Sykes has been kind enough to furnish me with respecting the 

 habits of D. Syhesii, subsequently detailed, prove that in regard to this genus 

 Dalman was correct in his supposition that insects with prominent eyes affected 

 moist situations, whilst the raptorial fore legs and the more developed structure 

 of the mouth show that his latter observation cannot be far from correct. 



As to the characters which constitute the specific distinctions observable in 

 the following insects, it is to be noticed, that from an examination of not less 

 than thirty-five specimens of D. Syhesll, variation in colour appears to be of 

 the first importance in this group. It will be seen, however, from Caiman's 

 observation upon D. slgnata, that even colour is liable to variation, although 

 evidently only to a slight extent. Scarcely the slightest variation in this respect 

 existed in any of the specimens of D. Sykesll. The length of the horns, which 

 Dalman gives as one of the leading characters of his D. macrophthalma, is, as 

 stated above, a sexual difference, and therefore ought not to be employed. 



VOL. xvn. 2 Q 



