British Species of Caddis-fties. 85 
the two first united; fourth about as long as the second; fifth 
nearly as long as the third and fourth united. Labial palpi long ; 
first joint short ; second long; third still longer, and thinner than 
the others. Mesothorax robust, ovate. Anterior wings rather 
narrow, the apex elliptical; very hairy, sometimes with short 
clavate hairs in the males, resembling scales (M/ormonia in part) ; 
sometimes the costa in the males is furnished with a long back- 
curved fringe (Helictomerus) ; apical fringes very long; discoidal 
cell long and narrow, closed; the female is furnished with two 
more apical forks than the male. Posterior wings nearly similar 
in shape to the anterior, but somewhat shorter ; fringes very long; 
discoidal cell closed ; neuration varying in the sexes as in the ante- 
rior wings. Legs moderately long; anterior tibiz with two 
moderately long apical spurs; intermediate and posterior tibize 
each with two pairs of long and equal spurs. Abdomen short and 
slender. In the males the superior appendices are very small; 
app. intermed. sometimes long; app. inf. very long, curved round 
and approximating at the tips; penis exserted and thickened at 
the apex. In the females the apex of the abdomen is obtuse, with 
a cleft piece, perhaps representing the valves. 
Larva and case similar to those of Scricostoma ; inhabiting run- 
ning streams. 
In all groups of insects there are some which apparently set at 
nought the recognized rules of classification, and while the close 
relationship of the different species is most evident, yet they 
differ in such a manner, that, if the usual laws of generic dis- 
tinctions be strictly applied, each individual species should form 
a separate genus. These vagaries of nature are most curious and 
interesting, but at the same time they puzzle the would-be clas- 
sifier, and prove to him the intensely artificial character of all 
attempts to break the indivisible chain of natural organisms. 
The genus Mormonia is almost an extreme instance of this (as it 
were) propensity to natural experiment. The different species 
all present general characters of the greatest resemblance inter se, 
yet the form of the palpi, a character almost universally acknow- 
ledged as one of generic value, differs more or less in each, 
and sometimes to a great extent. I am unwilling to unnecessarily 
multiply genera, and have therefore divided our three species into 
two subgenera, Mormonia and Helictomerus, leaving it to future 
students to adopt or reject this division as they think fit. 
A. Antenne not fringed in the male; maxillary palpi in this 
sex short and clavate (or ovate) ; costal margin nithout a 
