1880. 



131 



Dr. Mliller assumes, as results from the tenor of some passages 

 (especially oue on p. 41, left column), that in the Blepharoceridce, as 

 in a great many other Diptera, the eyes are contiguous in the male, and 

 separated by a distinct front in the female. But it is just in this 

 respect that the Blepharoceridce differ from most other Diptera ; their 

 eyes are contiguous in some genera and separated in others, but when 

 contiguous, they are so in both sexes, and when separated, likewise. 

 The weight of this statement is qualified, it is true, by the circumstance 

 that amongst twelve described species of Blepharoceridce, only four 

 are known in both sexes ; of the other eight only the males are known, 

 which execute aerial dances and are more frequently caught. It is 

 possible, therefore, that the species observed by Dr. Miiller differs 

 from the cases hitherto known, and has the eyes contiguous in the 

 male, while they are separated in the female. Moreover, Dr. Miiller 

 sta.tes explicitly that he examined the structure of the abdominal ap- 

 pendages of both sets of females, and found them to be the same in 

 both. If it had not been for this statement, one might have suspected 

 that the female without mandibular organs was in reality a male, and 

 that the male with contiguous eyes belonged to a different species. 



Another remark which suggests itself to me, is about the generic 

 name of Dr. Miiller's species. Dr. Schiner described a male Baltostoma 

 as having separated eyes ; Baltost. torrentium has them contiguous ; 

 this would, perhaps, constitute a difference of generic importance. 



The statement, finally, that Baltostoma occurs in Europe, and has 

 been found on Monte Eosa, is based upon some misconception. The 

 Blepharocerid discovered on Monte Eosa is Hapalothriafa, very abnor- 

 mal genus in that abnormal Family ; it has nothing in common with 

 Baltostoma but a superficial resemblance in the venation. P alto stoma 

 has been found in South America and Mexico only, 



If this article should meet the eye of Dr. Miiller, it will perhaps 

 induce him to furnish us with more facts about this interesting question ; 

 mature imagos should be caught, and the venation of their wings, as 

 well as the structure of the genital organs, carefully compared. 



Errors may easily occur. Thus, Macquart received from the same 

 locality specimens with contiguous and separated eyes, and described 

 them as sexes of the same species. It was found afterwards that they 

 constituted different genera, and that the specimens with contiguous eyes 

 {Blepharocera) were the females, while those with separated eyes 

 {JLiponeura) were the males ; exactly the opposite of what one would 

 have expected. 



Persons desirous of more iuformation about Blepharoceridce, I 



