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222 COLLEGE ENTOMOLOGY
gle also with the mud dwellers on the one hand and the cascade dwellers on
the other and may be found on or among aquatic plants in still pools.
The adults have comparatively few cross veins, and the hind wings are very
greatly reduced or wanting. There are two caudal filaments. The males of
some E::etis,l Cloeon, and Centroptt'lum have turban eyes. The claspers are foursegmented
although some are so poorly jointed as to appear but threesegmented.
The second segment is slender and often about as long as the first
and may be fused with the third which is much the longest and frequently incurved.
The apical segment is very small and not always distinctly separated.
This is also a large and cosmopolitan family represented by the following
important genera: Eretis Leach (widespread - the naiads often living in waterfalls),
Cloeon Leach (cosmopolitan), Centroptilum Eaton (Holarctic, Ethiopian),
Callib::etis Eaton (American), and Procloiion Bengtsson (Palroarctic).
Bmlt's pos/£catus (Say) is a common mayfly in the upper Mississippi River
valley. The small black and greenish-white adults, which have hyaline wings
and are but 8-19 mm. long, swarm early in May along rapid streams. Following
mating, the females alight on stones, crawl under the surface of the water,
attach gelatinous masses, containing from 80 to 300 eggs, to the surface of the
rocks, and then perish. The eggs hatch in a month. The naiads molt about
27 times and finally emerge as adults in October. These mate, lay eggs, and
give rise to another brood which emerges the following August. Thus there
are three broods in two years.
Family ClENIDJE 2 Klapiilek 1909 (Cre'ni-dre, from the Greek KIlLVOS, novel,
new, strange; in reference to the peculiar naiads).
The naiads are peculiar in having the second pair of gills very large and
elytrum-Iike, covering the succeeding pairs. The three caudal filaments are
nearly equal in length. They live under a variety of conditions, many of them
inhabiting sand or mud bottoms.
The adults have very few cross veins and no hind wings, three caudal filaments,
and their male claspers are horn-shaped and one-segmented.
The family is quite a large one with a wide distribution. The most important
genera are C;enis Stephens (cosmopolitan), Tricoryphodes Ulmer (American),
LeptohYPhes Eaton (South American), Leptohyphodes Ulmer (Neotropical),
Tricorythus Eaton (Ethiopian), Brachycercus Curtis (Palrearctic).
Family LEPTOPHLEBIIDlE Klapiilek 1909 (Lep'to-phleb-i'i-dro, from the
Greek Af7rTOs, fine, small, + rp"Al:{3wv, veinlet; referring to the slender veins).
The naiads are elongated, with fairly long antennro and three equal caudal
filaments as long as or almost as long as the body and with long slender leaflike
or string-like gills.
I This appears to be the correct form of this word since it is so printed in connection with the
brief description of !.he genus by Leach. Continuing on the same page (p. 137), however, the
spelling is changed to Bailtis when used with the species hioculalus, and is Bmlis in the index
(p.163). l'he first use has precedence (Leach. W. E., "Entomology," in Brewster, Edinburgh
Encyclopedia. vol. 9, pp_ 137, 163, 1815).
• AlsD BRACHYCERCIDlE Lestage 1917 (?).