16 Iutrnoris NaturAt History Survey BULLETIN 
Hagen did not return Walsh’s duplicate 
specimens to him, but added them to his 
own collection. Walsh sent specimens of 
additional species to Hagen in 1864; these 
Hagen added to his collection. Later, in 
1870, Hagen brought his collection to the 
United States and deposited it in the Mu- 
seum of Comparative Zoology, Harvard 
University. In the meantime, Walsh had 
died, in 1869, and his collection, containing 
the types of all his mayflies, was deposited 
in the Chicago Academy of Sciences. In 
1871, this collection was completely de- 
stroyed in the great Chicago fire. As a 
result, the specimens of Walsh’s species in 
the Hagen collection, still preserved at the 
Museum of Comparative Zoology, became 
the sole remaining authentic representatives 
of those species. 
It should be noted that, although the true 
types of Walsh’s species are destroyed, most 
of the specimens of Walsh material now 
in the Museum of Comparative Zoology 
may be considered to be cotypes. Some 
specimens, however, were collected by Walsh 
after the descriptions were published, as is 
shown by the specimen labels, and these 
specimens are only autotypes. Lectotypes 
for most of Walsh’s species of mayflies have 
been designated by Nathan Banks. A 
number of workers, myself included, have 
studied these specimens. “Table 1 gives a 
list of the species described by Walsh and 
the present status of the lectotypes. 
In addition to the species listed in table 
1, the Museum of Comparative Zoology 
collection includes specimens determined and 
labeled by Walsh as Baetis arida Say, B. 
alternata Say, Potamanthus cupidus Say, 
Palingenia limbata Pictet, Palingenia bilin- 
eata Say, Palingenia interpunctata Say, and 
Baetisca obesa Say. All were collected by 
Walsh at Rock Island. 
In collecting material for the present 
Illinois report on mayflies, we made a great 
effort to secure good series of all the Walsh 
species from the type locality. The results 
were somewhat disappointing, as, of the 31 
species described or identified by Walsh, we 
were able to secure only 8 at Rock Island, 
even with intensive collecting. This is not 
surprising when it is realized that the rivers 
around Rock Island are now quite different 
than they were in Walsh’s time. In the 
1860’s the Mississippi and Rock rivers at 
Rock Island were large, rapid rivers (Walsh 
Vol. 26, Art. 1 
1863: 202). Since Walsh’s time, extensive 
dredging, channel straightening, and dam- 
ming operations have greatly reduced the 
rapidity of flow of these rivers. As a 
result, the Mississippi River at Rock Island 
is now ecologically more like a lake than a 
rapid river, and the Rock River is extremely 
sluggish. Changes in the rivers have pro- 
duced a corresponding change in the local 
mayfly fauna. 
In Walsh’s time, also, it was the annual 
practice, in spring, to float log rafts down 
the Rock and Mississippi rivers to the saw 
mills located in Rock Island (Walsh 1862: 
372; 1863: 202). These rafts originated in 
the pine forests of Wisconsin and Minnesota. 
Walsh noticed that large numbers of mature 
mayfly nymphs were brought down the river 
to Rock Island with these rafts. The 
nymphs, in the accumulated debris of the 
rafts, crawled out on the logs to molt. Walsh 
collected much of his material from these 
log rafts. Needless to say, this source of 
specimens long since has disappeared from 
Rock Island. 
Although we collected only 8 of Walsh’s 
species at Rock Island, we _ ultimately 
secured 27 of his 31 species by searching in 
other localities. Most of the specimens we 
took at various points on the Rock River 
upstream from Rock Island, notably at 
Prophetstown, Dixon, Sterling, Oregon, and 
Rockford. Some also we took in southern 
Illinois at Mount Carmel, on the Wabash 
River. 
Of the Walsh species which have not 
been collected again in Illinois, Ephemerella 
excrucians has recently been reared in 
northern Michigan (Leonard 1949:158). 
E. consimilis, based on a very brief, com- 
parative description, and unrepresented in 
the Museum of Comparative Zoology col- 
lection, has of necessity remained unrecog- 
nized. Walsh identified Rock Island speci- 
mens as questionably belonging to two species 
described by other authors: Baetis debilis 
Walker and Cloe unicolor Hagen. ‘The 
former has been shown by Eaton (1885: 
253) to be a misidentification, but exactly 
what species Walsh had cannot now be 
determined. The latter was an identification 
of a Hagen species which is itself unrecog- 
nizable today. As we lack the original 
material, what species Walsh ascribed to the 
name unicolor cannot be ascertained with 
any degree of certainty. 
