PRePaAck: 
———— 
The completion of the fourth volume of the present work has come 
upon me somewhat unawares. It was begun with only the vaguest notion 
of its most natural order, and with no lines whatever to work upon in 
British literature less than forty years old. Gradually it built itself up, 
yielding to treatment, until the end was reached in an unexpectedly short 
time, for it has run concurrently with other work upon parasitic Hymen- 
optera, which has been thrust upon my hands. On the whole, my own 
opinion of the result as set forth in the present volume is fairly satis- 
factory, especially respecting synonymy, though some groups of the 
Tryphonides require further elucidation, and doubtless many more species 
of them will be found with us, in spite of the fact that the numbers of 
these parasites must always be proportionate to that of their known hosts. 
As regards the Bassides, Exochides and Metopiides, our knowledge is 
sufficiently full and will compare favourably with that of any country, 
especially in respect to the Orthocentrini, which have hitherto been 
everywhere regarded as among the most obscure and indefinite of all 
Ichneumonidae. 
Such difficulty as there may have been in the present volume has lain 
rather in the great number of our indigenous Tryphoninae, both in species 
and individuals, than in their correct identification; and the number of 
species would have been considerably greater, owing to the impossibility 
of synonymising the older authors’ names, were it not that Gravenhorst’s 
types have recently been revised in a very adequate manner. I came to 
the task facing four hundred and thirty-five species, distributed through 
only thirty-eight genera, according to my revision read before the Ent. 
Soc. in 1901; and this mass has now fallen to three hundred and thirty-four 
species comprised in forty-nine genera. In respect to the genera, a great 
many more would have been necessary to embrace all those erected by 
Thomson and Forster; but I do not at all advocate the adoption of 
genera unless the insects present features of pronounced distinction ; a 
genus is an artificial division to be made use of solely for convenience in 
nomenclature, and the fewest convenient number should always be 
adopted. Only the strictest synonymy can account for so great a reduc- 
tion in the number of species, a few of which have been omitted from the 
indigenous Catalogue at the end of the volume on the ground of their 
doubtful occurrence here, though all such are invariably referred to at 
their correct location in the body of the work. ‘The majority of these are 
of wide Continental distribution, and the ever-increasing number of our 
students will soon prove them to be British; the frequent breeding 
2 O2ARS 
