PREFACE. Vll 



siclered them to be distinct species, which has added vastly to their 

 cumbrous synonymy. Besides being unnatural, however, this method 

 adds nothing to the convenience of determination ; and I have 

 described them collectively, taking care to clearly indicate what 

 peculiarities appertain to one sex only. 



In the tables prefixed to each genus, too, this method has been 

 adopted, and points of sexual agreement have been chosen whenever 

 possible, rather than more obvious ones existing in one sex alone. 

 Consequently, these tables, though of sounder foundation than sexual 

 ones, are slightly more difficult to follow, and they are intended to be 

 taken, not as the alpha and omega of identification, but as mere 

 guides to the fuller descriptions. 



My object throughout has been rather to put what was already 

 known, though in so scattered a form, of our indigenous species into 

 concise and easily assimilated fashion, than to bring forward additional 

 or new species and original observations upon them, but these have 

 been inserted wherever it has happened to be my good fortune to 

 meet with them. Beyond this, it was very necessary that British 

 students should become familiarised with modern Continental and 

 American methods of classification and nomenclature, regarding which 

 nothing whatever was to be ascertained from our own literature, since 

 it has been an unbroken tenet to take the now obsolete Marshallian 

 list as a basis for all work. Sound and fundamental as this list 

 undoubtedly was thirty years ago, more recent investigation and the 

 inevitable evolution of the study since 1872 have brought to light new 

 facts, which cannot, on the plea of their many subtilities, be ignored. 



Concerning the distribution of these insects with us, the study is 

 too young for any definite statement to be reliable ; and I will only 

 say that, in spite of what Berthoumieu has written to the contrary, 

 I am of opinion that their greater or less prevalence is not due to the 

 frequency of Lepidoptera and their larvae in general, but to that of 

 those kinds of them which are peculiarly subject to parasitic attacks. 

 Many hundreds of hosts are now known in the Ichneumoninae alone, 

 yet a very large proportion of the commoner lepidopterous insects 

 which one would expect to find freely preyed upon are, as far as is at 

 present known, entirely immune from attacks. McLachlan and J. J. 

 AVeir have referred to the larvae of Cucullia and Dilobn, both of 

 which are conspicuous, but for long supposed to be free from attack ; 

 and Bates has pointed out that information is also required as to what 

 larvae are most subject to ichneumonidous onslaughts, and has asked 



