61 



classer les Hymenopteres et les Dipteres ; 1807) named "Bullae," 

 observed by him in the wings of certain hymenopterous insects. 

 It is strange that for eighty years these " Bullae " or " Pores " 

 have been either ignored or forgotten by succeeding dipterists. 

 Not having M. Jurine's work to refer to, I cannot state what 

 are his views with regard to these " Bullae," but judging from 

 the name bestowed (buHa, a boss or stud), he did not think they 

 were of the nature of pores. On the other hand Mr. Skuse 

 suggests that they are for the purpose of aerating the blood 

 coursing through the veins. If this be their object the term 

 " pore " is correct. Considering that some of the families of the 

 the Di]3tera do not have them, that their position is limited to 

 certain veins, viz., the junction of the first longitudinal with the 

 costal, the third longitudinal, and the middle transverse vein ; 

 and that in some places the pores are close together, whilst else- 

 where they are relatively far apart, it really seems that if such 

 be their object, nature was extremely capricious in arranging 

 them and that she had neglected in this case that close adap- 

 tation of means to an end that characterises her work. 



So far as my observations have extended, it would appear that 

 the Diptera possessing large scales or hairs on their veins 

 (Cidicidce, Pscychodidce, Tipulidce) have no pores ; while the 

 Mtiscidce, SyrpJiidcf, and Dolichopodidrf' have them. With one 

 excejDtion, a Dolicltopodida, there is always a solitary pore on 

 the middle transverse vein, and in this case the third longitudinal 

 is so enlarged at this sjDot that the pore would otherwise be situ- 

 ated on the mid - transverse vein (fig. 8). My observations 

 have not as yet extended to the Hymenoptera, but judging from 

 Mr. Skuse's remark, only certain families possess them, as in the 

 case of the Diptera. 



Now that the attention of dipterists is called to these facts it is 

 to be hoped that before long their true nature may be satisfac- 

 torily settled, and that they may sometimes be found of value in 

 settling doubtful cases of affinity. 



EXPLANATION OF PLATE IV. 



Wings of the following Families, Genera or Species of the Diptera, showing 

 the position of the pores. 



Family Oscinidte ? I. Lestophonus Iceryae. 2. L. monophlebi. 2a. Por- 

 tion of the 3rd longitudinal vein showing dilation with pores. 2b. A pore very 

 greatly magnified, 3. Sp. ? 



Family Muscidas. 4. Musca domestica. 5. Calliphora sp. 



Family Tachinidce. 6, Tachina ? sp. 



Family Syrphidce. 7. Sp. 



Family Dolichopodidcc. 8, Sp. 8^?. A portion of mid-transverse vein, being 

 greatly enlarged. 



