109 



11. Lihellulina, nymph. 



Much like 9, but with smoother body, aucl lack.s the 

 cephalic tubercles. A distinct dusky bar between tlie eyes. Legs 

 annulate with dusky. Dorsal spines not cultriform, and not ele- 

 vated behind. Not as common as the two preceding. 



Localities: Lily Lake, Long Lake. 



12. Lihellulina, nymph. 



Similar to number 9, and possil)ly the young of the same 

 species. Tubercles of head relatively much larger. Dorsal spines 

 tuberculiform, erect. Body moi-e slender, nearly uniform blackish 

 brown. 



Two small examples from Willow Slough. 



OKDER EPHEMEEID^. (May Flies). 



Wings four (sometimes two), net- veined, the posterior pair 

 much the smaller. Mouth parts rudimentary. Antenn?e minute, 

 bristle-form. Prothorax very small. With two or three long 

 caudal appendages. Larvie with branchiae attached to the sides of 

 the abdomen, in the larger and commoner species overlying the 

 back. Pupa active. 



The adults of certain species of this grouj) are familiar to any 

 one who has visited our rivers in July. They blacken the willows 

 at the water's edge and cause the limbs to droop, in such quantities 

 do they collect upon them. In the evening, at times, they mount 

 into the air, and may be seen in countless numbers moving for 

 hours in one direction as if bent on migration. They are excel- 

 lent food for fishes, as is attested by the avidity with which many 

 of our fishes eat them, and were used as bait by sportsmen 

 in the days of Isaac Walton. The winged insect takes no food,, 

 and lives only for procreation, but may, in confinement, live a 

 week or more. The eggs are dropped into the water or are placed 

 upon plants, the flies descending into the water for this purpose. 

 The larvfe (nymphs) devour earth and sand containing dead and 

 living animal and vegetable matter. 



Hexagenia bilineaia, Say. 



This is the common brown May fly of Illinois rivers and lakes. 

 It occurs throughout the length of the State, and often in such mul- 

 titudes as to have acquired the name "mormon fly". It is com- 

 monly very abundant in the middle of July. In August, at Quincy, 

 it was rare. 



H<'i'(i<fcnia, nymph. 



An elongated, whitish creature, to be distinguished from most 

 other aquatic insects by the presence of seven pairs of branchije, 

 six of them plumose, attached along the sides of the abdomen 

 and carried turned over the back. Jaws long and curved; front 



