1873.] 231 



the natural state of a stream for liis own benefit are of use to the col- 

 lector, for if the placid course of a slowly flowing stream be changed 

 to a foaming waterfall by a weir or water-wheel, the congenial condi- 

 tions are at once seized upon by species which othermse might be 

 sought in vain. In fact, it is probable that more species frequent 

 running than standing water, and it is this that makes the torrents of 

 alpine regions so particulai'ly productive ; the cold is no hindrance, 

 they may be found up to the snow-limit, and delighting in the vicinity 

 of a glacier. So marked is the necessity of certain aquatic conditions 

 for the well-being of particular genera or species, that the water- 

 system of a particular district or countiy can often be understood by 

 an inspection of a collection of caddis-flies from it. Thus, I once 

 examined a large collection of species from Holland, which told as 

 plainly of a low-lying flat country "without mountains or torrents aa 

 could the most elaborate map. A certain amount of shelter in the 

 perfect state is absolutely necessary to TricJwptera, and for this 

 reason streams flowing over barren rocks are not productive. The 

 acme of success may be obtained when the stream is fringed with low 

 overhanging bushes ; the net should be placed as far under the bush 

 as possible, and the latter beaten vigourously over it, taking care that 

 the net itself do not come off its handle, or it may go sailing away 

 down the stream at a rate anything but agreable to the astonished 

 collector : such a contretemps has more than once happened to the 

 writer. In moorland districts there are often streams which have cut 

 their way through the peat, fringed with heather and other herbage ; 

 these are localities that should never be neglected. Light powerfully 

 attracts some species, and unique or rare forms have more than once 

 been found on gas lamps in the suburbs of London. It has also been 

 recommended to hang a white sheet near water, the insects being 

 attracted by it after dark, and settling on it. Tree trunks and walls 

 near water should always be examined ; on such positions the minute 

 and excessively rapid species of HydroptilidcB often absolutely swarm. 

 But, after all, experience — that " hardest of all schools," as I have seen 

 it termed — is the one thing to be gained and acted upon. 



Triclioptera should be set exactly as are Lepkloptera (premising 

 that the excessively low setting mentioned at the beginning of this 

 paper be eschewed), but must remain upon the setting boards longer 

 than is necessary for insects of the latter order. Relaxed and re-set 

 specimens take an especially long time before it is certain that the 

 wings will not ultimately fall back. Much care should be exercised 

 in re-setting with regard to the management of the hind-wings, which 



