142 A BOOK ON ANGLING 



to small fragments of stick, sand, stone, and shells, until it 

 has constructed a small, rough, hard tubular case, within 

 which it can shroud itself completely. One end of the case is 

 left entirely open, and from this the animal at times, when 

 it desires to shift its position, protrudes its head and feet, 

 and travels along, drawing the case after it ; the other end 

 is in many species partially closed, leaving only a round air- 

 hole, which fulfils a curious purpose in insect economy. It 

 is in the power of the larva to raise itself to the surface of the 

 water by secreting within the tail end of the case a small 

 portion of air sufficient to buoy up the weight of itself and 

 its habitation, and by means of this it may often be seen 

 hanging, as it were, from the surface of the water, apparently 

 basking with its tail upwards ; but at the least alarm or the 

 slightest touch the air-bubble is expelled through the round 

 hole alluded to, and the creature drops at once to the bottom. 

 When it is about to change into the pupa form, the larva 

 closes up the tube, and thus in a sort of cocoon becomes a 

 pupa, the wing cases, etc., being developed, as in the Ephe- 

 meridae, but rather more perfectly. When about to change 

 into the imago, some of the species tear open the closed-up 

 entrance and crawl to the bank of the river, and there abandon 

 their case, and become the imago. Some of the smaller 

 species, however, by the power above mentioned, rise to 

 the surface, and take wing from their cases, using them as 

 a sort of raft. These cases are beautifully smooth and 

 polished on the inside, and well adapted to the creature's 

 habits. The rest of its existence is similar to that already 

 described for the Ephemeridae, save that it is somewhat more 

 prolonged. 



As I am not writing a work upon entomology, it is not worth 

 while to occupy further space by describing the history of the 

 other various orders. It will suffice to say, that they all more 

 or less go through somewhat similar transformations egg, 

 larva, pupa, imago being the progress of their existence, which 

 is carried out either in the earth, or in animal or vegetable 

 matters, in the droppings of cattle or the bark of trees. Nor 

 should I have ventured to dip even thus far into the science 

 of entomology, save to dispel errors of belief and judgment, 

 which often produce in practice results unfavourable to the 

 angler's interests. I trust, however, that these explanations 

 may be found so far interesting to the angler as to call for no 

 further apology for their introduction. 



