323 



nematode, but having had so far no opportunity of submitting it to an 

 authority on the group I can not present any definite information as to 

 its identity. 



The following observations regarding the family status of the 

 genus may be of interest to students of the Nemocera. 



The genus Mycetobia presents in the larval stage what, judging 

 from our present very meager knowledge of the family, is a departure 

 from the normal mycetophilid respiratory system in having no lateral 

 abdominal spiracles. In fact the lateral tracheal branches simply fork 

 and have no terminal extension which would seem to indicate the re- 

 cent possession of abdominal spiracles. This is not. to my mind, in- 

 compatible with their position in this family, though there are some 

 writers who may differ from me upon this point, — e. g. Osten Sacken, 

 who considered that the genus does not belong to the Mycetophilidcu 

 because of the closed spiracles. In this connection it seems necessary 

 to mention a recent paper dealing in an arbitrarv manner with the 

 classification of this group.* In the paper referred to there is a sum- 

 mary of facts deduced from the writings of investigators, principally 

 Brauer, unsupported by any other data in possession of the compiler, 

 by means of which the latter endeavors to outline what he considers to 

 be a natural classification of the families in the group. I have the con- 

 viction that a natural classification can only be arrived at by a careful 

 consideration of the characters possessed by all stages taken in con- 

 junction with their mode of life. It is impossible, to my mind, to 

 arrive at a decision as to the importance of certain organs as a means 

 of Classification unless we know how the species live, what is the im- 

 portance of the organs in the habitat, and, finally, to what extent a 

 departure from a certain mode of life may affect one set of organs in 

 comparison with others that seem to be of less fundamental signifi- 

 cance. That we may, and do, find species in a family with certain or- 

 gans functional which in others are vestigial or even absent, is not suf- 

 ficient reason for the separation of such species into different families, 

 and though the respiratory system is of more importance probably 

 than any other one character, I consider that it is absurd to lay down 

 any rule of classification based upon that one character, which is admit- 

 tedly variable in most groups of insects, especially in view of the fact 

 that we are unacquainted with probably ninety-five per cent, of the 

 species included, in so far as their larval stages are concerned. 



Another, and most reprehensible attitude is that taken by the writer 

 previously referred to when he discounts the evidence brought for- 



*The Nemocera not a Natural Group of Diptera. Ann. Ent. Soc. Amer., Vol. 8, 

 1915, p. 93. 



