WILLISTOX: APIOCERID.^. 105 



as follows: ■'•'Closely allied to Miirodetiis Gerstaecker, as there are 

 three cells interveaing between the forked cell and the margin of the 

 wing, and as the structure of the proboscis is the same, long and linear, 

 directed forwards, with very narrow lips at the end; differing, however, 

 from that genus in the structure of the antenna, in some minor 

 charactersof the neuration * * ; and in the presence of two [three] 

 distinct ocelli" (i6). The only difference in the neuration that can be 

 expressed lies in the shorter discalcell, and it is on the strength of this 

 that Osten Sacken traces a relationship with the Asilidse. By com- 

 paring the figures it will be seen that the Xemistrinid neuration 

 offers the same peculiarity. 



"I believe that a natural arrangement [of families] must be the 

 result of the study of those organs of the imago which are necessary 

 for the functions of external life, principally, therefore, of the organs 

 of orientation connected with the head (eyes and antennge), and in the 

 second line, of the organs of locomotion (legs and wings)."* To this 

 Osten Sacken should have added, as among the most important, 

 the mouth-parts. Certainly there can be nothing which affects the 

 habits of the adult insect more intimately than do the organs by which 

 food is taken into the body. Xow, if we admit that the neurational 

 resemblance between Trie/onus and Rhaphioviidas is of secondary 

 value only, we must find Asilid resemblances in the head to counter- 

 balance it. The actual fact is, however, that the mouth-parts of the 

 TriclonincE, if I may use that term to indicate the three genera, 

 Diochlistus, Mitrodetus and Triclomis, are, if Tricloniis can be 

 taken as a type, quite like those of Rhaphiomidas and Apiocera, and 

 fundamentally different from the Asilid type. We have then left 

 from among the important characters, according to Osten 

 Sacken, only the antennae, which are Asilid and not Mydaid, and the 

 ocelli. But, the difference in the antennse is not so radical as that 

 which occurs between Lepiis and Arthroceras, for example, and 

 Osten Sacken has expressed the opinion more than once that these 

 forms belong together, an opinion with which I coincide. 



Another Asilid argument is left, one on which Doctor Osten Sacken 

 places great weight, — I mean the presence of thoracic bristles in 

 the Apioceridae and their entire absence in x\it Mydaidce. Although 

 fully admitting that too little attention has been given to the chae- 

 totaxy of diptera, I cannot accept the argument as one outweighing 

 those derived from the important differential characters in head and 

 neuration. As Mik has pertinently said (12), the presence or en- 

 tire absence of well-developed bristles among the Syrphidae is of less 

 than generic value. 



*Eutom, Monthly Mag. [3] p. 35, 18 Jl, 



