NOTES ON THE NATURAL HOSTS OF FRESH-WATER MUSSELS. 
By THADDEUS SURBER, 
Assistant, United States Biological Laboratory, Fairport, Iowa. 
A study of the conditions pertaining to natural infection of fishes with the larvse 
of fresh-water mussels was begun by the writer, under the direction of Dr. R. E. Coker, 
at the Fairport laboratory in 1910, but was interrupted by assignment to other work, 
and, while an effort was made to resume the study in 1911, but little was done owing 
to more pressing duty demanding the time. From the last week in June till the close 
of November, 1912, however, work was pushed rapidly, 2,815 fish being critically 
examined, and considerable knowledge gained in regard to certain mussel species. 
The observations given in this paper indicate that the natural hosts of our fresh- 
water mussels are divisible into two classes — i. e., specific distributors of particular species, 
and accidental or occasional hosts. To the first class belong the skipjack {Po^nolobus 
chtysochlor is), distributor of the niggerhead {Quadrula ebena) ; the sheepshead {A plodinotiis 
grunniens) , distributor of the paper-shell (Lampsilis Icevissima) and the deer-toe (L. dona- 
ciformis) ; and the shovel-nose sturgeon (Scaphirhynchus platorhynchus) , distributor of the 
slough sand-shell (L. fallaciosa). The sauger {Stizostedion canadense) may belong here 
as distributor of another sand-shell (L. higginsi), but it would be unwise to conclude this 
on the strength of a single specimen. To the second class, in order of their importance, 
belong the crappie (Pomoxis annularis), which has been observed to carry six species; 
the sauger, carrying four species; two sunfishes {Apomotis cyanellus and Lepomis pallid us) 
each carrying three; the strawberry bass {Pomoxis sparoides), two species; and another 
sunfish {Lepomis humilis) and the white bass {Roccus chrysops), one each. A catfish 
{Anieirus natalis) carries a few glochidia of the Quadrula type, but I have not been able 
to identify the species, owing to accidental loss of material. 
Upon consideration, the first class (specific distributors) will be found to agree 
closely in geographical range with the species of which it is the host, as might be expected. 
This, of course, is not an original theory, but was advanced years ago by Simpson,® 
and I am convinced that he was right in his conjecture, and to that end shall attempt to 
show that it is the case in at least three species of our mussels. 
The second class of infections, accidental or occasional hosts, need not be taken up 
systematically at this time. Reference can be made to table ii, however, which shows 
the species and number of fishes that were observed to be infected with the various 
species of mussels. 
“Simpson, Charles T,: The pearly fresh-water mussels of the United States; their habits, enemies, and diseases, with 
suggestions for their protection. Bulletin U. S. Fish Commission, vol. xvni (1898). p. 282. 
