€ ORY 
III. Descriptions of new or little-known Genera and 
Species of Exotic Trichoptera; with Observations 
on certain Species described by Mr. F. WALKER. 
By Rosert M‘Lacutan, F.LS. 
[Read 2nd October, 1865. ] 
Tue greater number of the exotic caddis-flies described in this 
paper were collected in the islands of the Malayan Archipelago 
by Mr. A. R. Wallace, and are contained in the collection of Mr. 
W. Wilson Saunders; others are in the British Museum or in my 
own collection. ‘The paper may be considered as pretty well ex- 
haustive of the new species existing in collections in this country, 
excepting a few of which there are only solitary and much 
damaged examples. I cannot but regret that in many instances 
the descriptions have of necessity been drawn up from single 
specimens. The number of new genera, compared ced that of 
new species, is very considerable. 
The more [ become acquainted with the value of generic cha- 
racters in the Z'richoptera, the more am I convinced that, as in 
Hymenoptera, the neuration of the wings (combined with the 
leg-spurs and palpi) furniShes the safest starting-point for the 
formation of generic divisions. The wing system is not absolutely 
infallible, and is to a certain extent arbitrary, as indeed is the case 
with all schemes devised to facilitate the classification of natural 
objects, but it affords easily-seizable characters; care must, 
however, always be taken to avoid mistaking sexual for generic 
differences. In the family Limnephilide alone the wing-system 
appears to fail, the neuration of all the genera being almost iden- 
tical ; here too the palpi are of small value for generic diagnosis ; 
and we are compelled to fall back upon the tibial spurs and other 
characters. 
With respect to the abundance or paucity of tropical and 
southern T’richoptera, there are scarcely sufficient data to gene- 
ralize upon. The number of known South American species is 
very small, yet Mr. Bates informs me that on the Amazons they 
were sometimes so abundant as to extinguish the lamps ; in the 
VOL. V. THIRD SERIES, PART III.—JUNE, 1866, s 
