132 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 



in the open, but in the laboratory they were observed to crawl up the sticks placed 

 in the breeding-jar for the purpose and transform just above the water-level. 

 The subimago stage generally lasted a day, but in the early part of the season it 

 quite frequently lasted 3 days, and in a couple of instances 4 days. No doubt 

 this time would have been shortened had the subimagos been out of doors. The 

 imagos never appeared in large swarms as in the case of Ephemera and Hexagenia, 

 but a swarm would consist of perhaps 50 to 100 individuals. They would begin 

 their flight from three quarters to one half an hour before dusk, dancing up and 

 down in their rhythmic manner at a height of from 12 to 20 feet. On calm even- 

 ings they could be found in numerous swarms all along the shore of the island, 

 but on windy evenings would congregate on the lee side. The females of all the 

 species observed at Station Island deposited their eggs by skimming the surface 

 of the water and brushing off the eggs as they appeared from the openings of the 

 oviducts. The earliest species was H. luridipennis , mature nymphs of which 

 were taken on the afternoon of May 31, and one subimago emerged the same 

 afternoon. The last was H. luridipennis, the imagos emerging Sept. 2, from 

 nymphs collected August 23rd. 



The following are the generic characteristics of the Heptagenia nymph: 

 Body flattened; head orbicularly rounded with flaring margins; eyes dorsally 

 placed; postero-lateral angles of abdominal segments produced into spines; femora 

 flattened; gills on segments 1 to 7, placed dorsally in an overlapping series and in 

 life move in waving undulations; lamellae oblong or oval pointed, the 7th small 

 and lanceolate. Branchial filaments bifid and united basally into a flat trian- 

 gular plate. Setae from one to one-and-one-half times length of body, spreading, 

 fringed with hairs at the joints of the segments. Mouth parts — lab rum with 

 width nearly twice the length and a row of short spines along the ventral surface, 

 just inside the anterior margin. Anterior margin densely fringed with hair. 

 Mandibles rather triangular in shape; fangs two in number, the exterior one of 

 the right mandible stouter than inner and separated along inner edge; the inner 

 fang bifid at tip. Mandible fringed with hair along .the exterior margin. Lacinia 

 of first maxilla externally rounded, the anterior part being beset with spines and 

 hairs. The internal margin beset with a very dense even row of hairs and fine 

 bristles and several spines at upper corner. Palpus 3-jointed, basal one small, 

 middle one stout, distal longer and more slender ending in a curved tip; a row of 

 short spines near the apex. Palpus hairy along outer and inner margins. 



Labium with two pairs of lobes. The outer oval and densely covered with 

 hairs; the inner more slender, more pointed and incurved; also hairy. The an- 

 terior end of the distal segment of the palpus densely beset with long hairs and 

 sharp pointed projections with teeth along inner sides, somewhat resembling a 

 rake. Beneath this crown is a chitinized ridge. Hypopharyax with a triangular 

 tongue; paraglossae extend outwards with ends curved slightly backwards. 



Generic characters of the imago: 



Fore leg of male as long or slightly longer than body. The lengths of male 

 -fore tarsi arranged in order of increasing lengths are 5, 1, 4, 3, 2; 3 and 2 equal 



