NOTES AND QUERIES. 261 



Herons and Watercresses. — In the April number of the ' Agricultural 

 Students' Gazette,' Miss Ormerod — so well known for her investigations of 

 the habits of injurious insects — contributes an interesting note showing the 

 prejudicial effect on watercress-beds which may be caused by the thoughtless 

 destruction of Herons. This observation reminds us of Darwin's remarks 

 concerning cats and clover, through the intervention first of mice and then 

 of bees (' Origin of Species,' chap. iii.). and is worth quoting. Miss 

 Ormerod writes : — " We all know that Herons eat fish ; in the present 

 instance trout are the kind especially under consideration ; also that trout 

 eat water insects of various kinds (in this instance the well-known * Caddis 

 worms ') which often feed partly or wholly on vegetable matter. But to have 

 these facts in sequence — in successive series — on one area of less than an 

 acre in extent, culminating in such destruction of the vegetable food (in 

 this instance watercresses) that on special investigation three-quarters of 

 the crop was found to be materially damaged, if not totally destroyed for 

 sale purposes, is what may be considered an only too complete observation. 

 It was on January 23rd that I received a bottle containing specimens of 

 injured watercresses, together with a plentiful supply of what are so very 

 well known as ' Caddis-worms,' that it is unnecessary to describe them. 

 Several of these trichopterous larvae were free from their cases, and thus 

 their somewhat cylindrical shape, horny head, leathery three following 

 segments, with a pair of legs attached to each, and white soft succeeding 

 segments were clearly noticeable. So also were the two strong curved 

 hooks, placed far apart, one on each side of the caudal extremity, of which 

 it is said the larvae make use to fix themselves where they may desire to 

 be stationary. These strong little hooks were a very striking point in their 

 economy, for on lightly drawing the larva along my finger, their catching power 

 was distinctly perceptible; or on drawing them along the woollen tablecloth 

 they raised threads of the wool. In due time the larvae go through their 

 changes up to the state of the four-winged flies, known as * Caddis flies,' or 

 ' water-moths.' These when at rest have the wings deflexed, and as a regular 

 thing both pairs are furnished with branching nerves. The front pair are 

 usually somewhat hairy, the hinder pair sometimes, if not always, folded 

 when at rest. Most of the kinds appear during the summer, and of the 

 vast number of species Stephens says (Illustr. Brit. Ent., Mandibulata, 

 vol. vi. p. 146) in general habit they greatly resemble each other, and from 

 the almost total uniformity of colouring that obtains amongst them, they 

 are extremely difficult to divide specifically from each other. In regard to 

 prevention of attack of these water-grubs, which was the object with which 

 the collection of specimens and report of investigations was sent me, I felt 

 very much at a loss, never having had experience in the treatment of 

 watercress beds on the scale of management for sale. It was obvious, 

 however, that poisonous applications, either to the leafage, or thrown into 



