258 PEESH-WATEE AQTJAEIA. 



the genus Baetis is the " March Brown " of the angler. The 

 larvse of the Uphemeridce may be found, either in their burrows 

 in the mud, or hiding under stones, in either stagnant or 

 running water. It is hardly worth one's while to hunt for 

 them specially, as they are so frequently found while searching 

 for other fresb -water animals; but they certainly repay the 

 trouble of keeping them when taken. They are generally 

 seen crawUng about the mud which is brought up with the 

 hand-net. 



The insects of the Perlidte family of the Neuroptera are 

 distinguished chiefly by the veins of their wings and by the 

 formation of their thoraces. The longitudinal nervures on 

 the disc of their wings are united by transverse ones ; 

 and the three segments of their thoi-aces are almost of equal 

 size. These flies have four brownish wings, and long and 

 tapering antennse. The wings are longer than the body, and 

 when folded, lie flat, overlapping each other, upon the crea- 

 ture's back. There are two, generally long, filaments attached 

 to the last segment of the abdomen. The larvag (Fig. 159) are 

 very similar in appearance to the perfect insects (Fig. 158). 

 They live in either stagnant or running water, but much 

 oftener in the latter than in the former; do not make cases 

 like the caddis-worms, nor burrow like the larvsB of the Day- 

 flies, but live freely in the water, crawling about aquatic plants 

 or under stones; are carnivorous, and feed upon small animal 

 life, especially upon the larvae of other insects ; and swim weU 

 with an undulatory motion of their bodies. The pupaa are 

 known from the larvae by the appearance of the wings in then- 

 cases. The aquatic Hfe of the Perlidce lasts for two or three 

 years, and when it comes to an end, the pupas climb up an 

 aquatic plant or something else which will take them above 

 the surface of the water, and then wait until the pupal 

 skin bursts and they are able to emerge from it perfect insects. 

 The females carry their eggs, for a time before they deposit 

 them, at the extremity of the abdomen. The flight of these 

 insects is slow and laboured, and some of the males do not 

 fly at all. The larva of Nemura variegata, sometimes called 

 by anglers the " "WiUow-fly," is the most suitable for the 



