118 Annals Entomological Society of America [Vol. IV, 



and fine meshed wire-cloth. Over this, a cheese-cloth tent was 

 erected, and in it a large number of nymphs were placed. The 

 records of the results obtained are as follows : 



May 8, 12 nymphs emerged before 12 M., transformed before May 9, 12 M. 

 All Females. 



May 10, 40 " " before 12 M., " before 12 M., May 9. 



All Females. 



May 12, 25 " " before 12 M., " May 13, before 12 M. 



All Females. 



That these nymphs emerged so regularly before noon was 

 doubtless due to the fact that the sunshine reached the tent only 

 at this time and in the late afternoon. Rearings were made as 

 long as the season lasted but neither among the reared specimens 

 nor among the nymphs collected could a male be found. A few 

 specimens of the same species were also collected in two other 

 streams near Ithaca, but no males were found. The fact that 

 no male specimens have been taken neither in collecting, or 

 rearing, indicates a case of parthenogenesis in this species. 



Female imago. Measurements. Length of body 10 m. m. Length 

 of setae 10 m. m. Color bright reddish brown with whitish areas on 

 the thoracic pleurae. Abdomen reddish brown slightly paler beneath 

 with the ventral ganglia marked by darker areas. Antennae brown, 

 paler at the base, the second segment very long. Thorax brown; legs 

 brown, the third pair slightly paler than the others; wings hyaline with 

 their bases shaded with brown and the veins very distinct. Setae brown 

 with their joinings distinctly lined with brown. 



SUMMARY. 



1. The physical features of Fall Creek make possible the 

 greatest variety of aquatic conditions. A study of the abundant 

 May-fly fauna which lives under these conditions has revealed 

 a series of striking adaptations to environment. 



2. One may best observe the nymphs and secure adults of 

 uncommon species by rearing the insects in their own sur- 

 roundings. For this purpose a new type of breeding cage has 

 been described and figured. 



3. Observations upon representatives of 17 different genera 

 have shown some interesting points in structure and ecology. 

 Among these have been described the structural adaptations 

 of various nymphs, the striking peculiarities of Ephemerella 

 nymphs, the emerging of Blasturus cupidus, the swarming of 

 Ephemera and Leptophlebia, and the egg-laying of Baetis. 



4. No male specimen of Ameletus was secured either by 

 collection or among 83 reared specimens. I have, therefore, 

 suggested that this species may present a case of parthenogenesis. 



