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BULLETIN OF THE BUREAU OF FISHERIES. 
form the cap and in many genera the cap attachment, both of which are then 
like the case itself. In other genera, however, the dregs of the contents of the 
silk glands are different in color and texture, and so the cap attachment and some- 
times the cap itself differs in these particulars. The attachment is simply the result 
of the efforts of the beetle to completely empty its silk glands of their contents 
and has no relation whatever to the development of the eggs. If this be the 
explanation of the construction of this attachment, the name “fag” is suggested 
for it, signifying the end or loose end, the latter or meaner part, of the weaving. 
In Tropisternus, furthermore, the tip often unravels and forms a sort of fringe, 
which carries the same idea a little farther. In Hydrous and Hydrophilus the last 
of the contents of the silk glands is gummy or mucilaginous and dries in the air, 
because the egg cases of these genera float on the surface of the water. In conse- 
quence the surface of the fag and at least the basal half of the cap are smooth and 
more or less shiny. The fag also is much stiffer than in other genera. It is 
possible, however, that a similar result would be obtained if the fag of the egg 
cases of other genera were dried in the air instead of under water. 
BIBLIOGRAPHY. 
Agassiz, Louis. 
1850. Lake Superior, its physical character, vegetation, and animals, compared with those of 
other and similar regions, with a narrative of the tour, by J. Elliot Cabot, and con- 
tributions by other scientific gentlemen. 8°, 428 pp., 8 pis. Boston. [The Coleoptera 
were by J. L. Leconte and included water beetles, some of which were new species.] 
Alt, Willy. 
1912. Ueber das Respirationssystem von Dytiscus marginalis L. Ein Beitrag zur Morphologie des 
Insektenkorpers. Zeitschrift fur wissenschaftliche Zoologie, Bd. 99, pp. 357-113, 34 figg. 
Leipzig. 
1912a. Ueber das Respirationssystem der Larva von Dytiscus marginalis. Ibid., pp. 414-443, 15 
figg. [These two papers give detailed descriptions and excellent figures.] 
Ashmead, W. H. 
1894. Descriptions of two new hymenopterous parasites from water beetles. The Canadian Ento- 
mologist, vol. 26, pp. 24-2.6. London, Canada. [The parasites were Ichneumon flies, 
Gausocentrus gyrini from a Gyrinus pupa and Cyrtogaster dineutis from a Dineutes pupa.] 
Aube, Charles. 
1838. Species generates des Coleopteres de la collection de M. le Comte Ddjean. Vol. 6. Paris. 
[This volume contains the water beetles.] 
Baker, Frank C. 
1916. The relation of mollusks to fish in Oneida Lake. Technical Publication No. 4, New York 
State College of Forestry, Syracuse University, vol. 16, No. 21, pp. 8-366. [Included 
a list of plants and animals found associated with the mollusks, among which were two 
dytiscids, one haliplid, three gyrinids, and two hydrophilids.] 
Baker, W. F. 
1894. Hydrobius fuscipes: Notes on its life-history, larval anatomy, etc. The Naturalist, pp. 327- 
333. London. 
Balfour-Browne, Frank. 
1908. On the British species of the genus Philydrus Solier. Entomological Record, vol. 20, pp. 
25-29. London. 
1910. On the life-history of Hydrobius fuscipes L. Transactions, Royal Society of Edinburgh, 
Vol. XLVII, Part II (1909-10), pp. 317-340, Pis. I-III. Edinburgh. 
1913. The life-history of a water beetle. Nature, Vol. XCII, pp. 20-24. London. 
