BURROWING MAYFLIES. 271 
eaten, which omission, in view of the very great diversity in size, form, and habits of 
different mayflies, detracts much from the value of his report. 
Materials for the present paper have been accumulated in the course of recent work 
done by various representatives of the Bureau of Fisheries in the Mississippi River. 
The most important part consists of field notes and specimens collected by Emerson 
Stringham in the vicinity of the big dam at Keokuk, Iowa. ‘This includes material for 
the life history of a species of Pentagenia, a genus whose immature stages have not 
hitherto been made known. An extensive collection of aquatic-insect larvae made by 
Dr. A. D. Howard in the course of a mussel-bed examination in Andalusia Chute, just 
above Fairport, Iowa, contains a considerable series of mayfly nymphs, mostly belonging 
to the group here treated. H. E. Schradieck collected adult mayflies on the grounds 
of the biological station at Fairport, Iowa, during the summer of 1916 and sent them 
tome. These adults are of the same species as are the immature stages from the mussel 
beds; thus they furnish additional evidence as to the mayfly population of the river. 
A. F. Shira, director of the station, sent me also the mayfly material from nine stomachs 
of the river herring (Pomolobus chrysochloris) collected by various persons. To this I 
have added data of my own, gathered during residence upon the shores of Lakes Mich- 
igan and Ontario and elsewhere. 
MISSISSIPPI RIVER COLLECTIONS. 
Since the pioneer work of Benjamin D. Walsh (1862, 1863, 1864) at Rock Island, 
Tll., the mayflies of the Mississippi have received little attention. Garman (1890) 
published a few observations on the habits of the adult and on the food® of the nymph 
of Hexagenia bilineata in the backwaters of the Mississippi bottom lands. 
But it has remained for the collections above mentioned, made by Emerson String- 
ham, H. E. Schradieck, and Dr. A. D. Howard, to add material data. Mr. Stringham’s 
collections, made by the waterside and along the Keokuk Dam, include adults, subi- 
magos, and nymphs taken at transformation. Mr. Schradieck’s collections, made from 
the walls of the biological laboratory at Fairport, Iowa, consist of adults that have flown 
from the river and alighted on the building. Dr. Howard’s collections, made with a 
dredge from the bed of the river in Andalusia Chute just above Fairport, are all nymphs. 
These three collections supplement each other remarkably well and give a better picture 
of the mayfly life of the river than we have had hitherto. 
Mr. Stringham’s collections were made between the middle of June and the middle 
half of September, 1916 (save for a few adults of an undetermined species of Heptagenia 
taken on May 29 and a single nymph of Siplonurus taken on June 7, and neither again 
recorded). They relate mainly to two species: Hexagenia bilincata Say (Pl. LXXI) and 
Pentagenia quadripunctata Walsh (Pl. LX XIII, fig. 15). Mr. Stringham’s notes were 
accompanied by specimens adequate for determination of the species. His record of 
the occurrence of these two species about the big dam is as follows: 
HEXAGENIA BILINEATA. 
JuNE 7.—One grown nymph collected. 
JuLy 12.—Yesterday I observed that a large, grayish-brown mayfly with two caudal sete was 
very abundant about the dam. Still more abundant to-day. 
a“ The food consists of earth richly charged with dead organic matter and with unicellular plants and animals. Such 
protozoans as Euglena are quite commoninit. A large part of the contents of the digestive tube is sand, which seems to be taken 
incidentelly”’ (loc. cit., p. 180). 
