INTRODUCTION. 25 



limits, and there are but very few forms of transition from the one 

 to the other. 



The Eriopterina, through the entire disappearance of the short 

 anterior branch of the second vein in Goniomyia, may show a 

 leaning towards the group of Limnobina anomala; on the other 

 side, some genera of Eriopterina may come very near those 

 Limnophilina which, with only four posterior cells, combine ex- 

 ceedingly small, almost obsolete, spurs at the tip of the tibia?. 

 These connections are as yet very obscure, and we have to wait 

 for further discoveries. Another question which may be natu- 

 rally raised here is, whether Gladura, which alone among the 

 Eriopterina has five posterior cells, is not rather to be considered 

 as a genus of Limnophilina, the tibial spurs of which have be- 

 come obsolete. A more detailed study of the organization of 

 Gladura will have to show on w T hich side its relationship is the 

 strongest. The Anisomerina, especially the genus Eriocera, are 

 closely related to the Limnophilina ; but the number of antenna! 

 joints establishes a distinct limit between the two sections. 

 Intermediate forms are, as yet, unknown, although they may be 

 in existence. Trichocera, the only genus among the Limno- 

 philina, which has pubescent eyes and the subcostal cross-vein 

 far remote from the tip of the auxiliary vein, shows, in this 

 respect, a leaning towards the Amalopina ; in other respects, 

 however, its relationship to the Limnophilina is manifestly 

 stronger. 



The more characters peculiar to each one of the sections we 

 accumulate, the stronger we render the basis upon which the 

 classification is established and easier the solution we prepare for 

 all future doubtful cases. In this respect, a great deal yet re- 

 mains to be done. The progress of this study depends very much 

 on the observation of fresh specimens, and these cannot always be 

 had when wanted. Thus very good characters may be derived 

 from the comparison of the size and structure of the different 

 parts of the thorax and of the abdomen ; especially of the seg- 

 ments of the latter preceding the forceps. But these parts are 

 subject to shrinkage in drying, and in this state it is easy to take 

 an erroneous view of them. It is for this reason that I have 

 abstained from entering upon their detailed description. The 

 structure of the other soft parts of the body, as the palpi, the 



