1911] May-Flies of Fall Creek, N. Y. 103 



pressed slightly downward and inward when feeding. Some- 

 times the labial palp is slipped between the median (fig. 1, 1. e.) 

 and the lateral flaps (fig. 1, 1. d.), sometimes over the inner 

 sides of both. In the first case the plates on the outer sides of 

 the palp are brushed by the hairs on the inner side of the median 

 flap while the semi-circular patch of hairs (1. b.) on the inner 

 side of the palp is brushed by those on the outer side of the lateral 

 palp. In the second and more frequent case the outer side of 

 the palp is brushed by both flaps and the semi-circular patch 

 of hairs fits into the chitinized gutter on the adjacent surface 

 of the hypopharynx (hy. a.) Directly above the median por- 

 tion of the hypopharynx are the grinding surfaces of the maxillae 

 (mx. b.) with those of the mandibles (md. b.) directly above 

 them. Food scraped inward by the labial palps is evidently 

 deposited beneath the hypopharynx. From here it is probably 

 sucked up into the mouth cavity through the slits between the 

 median and lateral folds. The maxillary palps act in a manner 

 similar to those of the labium, but because of their position 

 above the hypopharynx, they must be able to place the food 

 directly in the mouth cavity. The inwardly curving hairs on 

 the lateral borders of the labrum help to keep the food in the 

 mouth while it is being chewed up. 



The foregoing observations were made by placing a nymph 

 in a shallow dish of water, throwing a strong light upon it and 

 studying it with a binocular microscope. The nymph was 

 uneasy in this unnatural position and kept its mouth parts 

 continually moving. Nymphs may be studied under more 

 natural conditions if they are placed in a glass-bottomed box 

 with a small amount of forage. The box may be placed upon 

 some support which will elevate it above the table. The bot- 

 tom may then be tilted at any easy angle and the nymphs 

 studied with a hand lens from beneath. 



Occurrence, habitat. The dates on which nymphs or ima- 

 goes were collected range from May 1 to June 15. These 

 nymphs were all taken in cool, shaded waters and were most 

 abundant during the early part of the season. The data for 

 those reared in cages is as follows : 



1 male emerged May 11, a. m., transformed May 13, a. m. Coy Glen. 

 1 male emerged May 12, a. m., transformed May 14, a. m., Pleasant Brook. 

 3 females emerged May 30, p. m.. transformed June 1, p. m. Pleasant Brook. 

 1 female, 1 male emerged June 10, a. m., transformed June 12, M. Fall Creek. 



