VIII MAY-FLIES 323 



company with Heptagenia, sheltering itself in the 

 mud. 



II. LarvcB ivith flattened bodies. — -Ecdyurus flumi- 

 num, a large species found in clear, stony streams in 

 hilly districts, or Heptagenia, will serve to exemplify 

 this section. All parts of the body are flattened out ; 

 the head is semi-circular and the legs very broad. 

 This flat shape enables the larva to cling to stones, 

 and escape the full force of the stream. The leaflet 

 of the gill is well developed, and the filaments small. 

 They make no burrows, but when disturbed they 

 swim with tolerable ease. They are carnivorous, and 

 prey upon small aquatic larvae. 



III. Swimming Larvce. — The common Chloeon, 

 which is found in pools, ditches, and small rivulets, 

 is adapted for swimming in preference to other modes 

 of locomotion. The legs are weak, but the tail- 

 filaments, all broadly fringed on both sides, form an 

 efficient tail-fin. The tracheal gills consist of leaflets 

 without filaments. The larvae feed on small anim^^* 

 which they find among aquatic plants. 



IV. Creeping Larvce. — Here Pictet places some 

 larvae of which Ephemerella is the best example. 

 Not possessing limbs adapted for digging, nor means 

 of rapid locomotion of any kind, it inhabits streams 

 of moderate swiftness. The tracheal gills, which are 

 reduced to four pairs, are protected by large and firm 

 leaflets. To escape its enemies and pounce unseen 

 upon its prey, it covers its body with a thin layer of 

 mud, which clings tenaciously to the fine hairs with 

 which the integument is furnished. Some Perlidai, 

 as Pictet remarks, have the same instinct. So has an 



Y 2 



