REPORT OF THE SECRETARY. 11 



individuals. Hence, it may be considered as one of the most interesting 

 families of the order. Nevertheless, but little has been done as yet for 

 the exact definition of its limits nor for its subdivision into smaller 

 groups. It was, therefore, impossible to attempt a satisfactory descrip- 

 tion of the North American species of the Ortalldcv without first settling 

 the question of the true limits of the family, of the relationship of it to 

 other families, and of the character upon which it is established. This 

 preliminary work the author thinks he has successfully accomplished, 

 and presents his reasons for this in an introductory chapter, in which is 

 reviewed what has previously been done on this point. 



The Trypetidce given in this part of the general work may be con- 

 sidered as a supplement to that published on the same family in the first 

 part of the series. This supplement has been rendered necessary by the 

 number of species of the family which have been found since the date 

 above mentioned. At that period only twenty-three North American 

 species were known. Since then the number has reached sixty-one, be- 

 sides a number of species of previous authors of which information has 

 since been procured. The author has, therefore, adopted the form of a 

 supplement to his previous paper. 



The following remarks in regard to the series, are by Baron Osten 

 Sackeu : 



"As this will probably be the last volume of the present series of the 

 publication of which I have the care, a few words with regard to the use 

 and aim of these volumes may not be out of place here. The diptera, 

 from the minuteness of their size and the extreme delicacy of the charac- 

 ters, upon which their classification is based, are without any doubt the 

 most difficult to study of all the orders of insects. To the general difficulty 

 of the subject, the North American diptera add another one in their analo- 

 gies with the European fauna on the one side and the South American 

 on the other. At the same time the dipterological literature in the Eng- 

 lish language is not a rich one. The only eminent English dipterist, Mr. 

 Haliday, published so little that his superiority was known to his cor- 

 respondents much more than to the public in general. Other English 

 publications which exist are utterly insufficient for any scientific pur- 

 pose, and more apt to mislead than to teach. Now the volumes of the 

 Monographs, although they embrace but an inconsiderable fraction of 

 the whole dipterous fauna of this continent, show at least how the sub- 

 ject has to be treated, how descriptions are to be drawn, what charac- 

 ters have to be noted, what analogies with the European and South 

 American fauna occur, and with what care they have to be studied in 

 order to distinguish analogy from identity. Moreover, three of those 

 four volumes are the work of the first dipterologist now living, who, 

 after Meigen, may be considered as the founder of scientific dipterology. 

 For all these reasons, I hope that the labor and expense bestowed upon 

 these publications will, after a time, bring its fruit, although it may not 

 be immediately." 



