Xil PREFACE. 
parison of the entire system of the neuration facilitated, 
which will be found sometimes necessary to detect their 
differences when resembling. The generic descriptions 
will, however, at once correct any inadvertent error that 
may be made, by displaying the combination of characters 
which corroborate the differences traced in those organs, 
and which I have selected by preference as their most 
simple expression. 
To add to the convenience of Entomologists, I have 
given, at the end, two copies of the nomenclature of the 
genera and species, printed upon hard paper; the one for 
the purpose of labelling their collections, and the other as — 
an index to their possessions : and I hope I have added to 
its utility by introducing the sexual signs, for no species 
can be considered complete with but one sex only. 
In conclusion I beg to return my sincere thanks to my 
numerous Entomological friends, for it is impossible to 
enumerate them here, both for the facilities they have 
afforded me in describing the rarities of their respective 
Collections, and the liberality with which they have con- 
tributed to my own; and to my friend Mr. Frederick 
Smith I am indebted for engraving my plates. 
31, Robert Srreer, Cuersea, 
December, 1836. 
