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HUNGERFORD: AQUATIC HEMIPTERA. 151 
the resemblances would be perfect. Not only is the shape the same, the 
“blossom end” being plainly suggested, and the exposed upper side being 
slightly more convex than the lower, but the streakings fade out below 
in a very similar manner. However, a closer inspection reveals a different 
feature at each end. At the free end, just below the “blossom scar,” 
there is an obliquely-placed white crescent, whose arms extend down upon 
the sides and mark out the cap that the young Benacus will later push off 
at hatching. The brown lines of the under surface stop short at the edge 
of this crescent; they are still more abbreviated at the opposite end of 
the egg. At the basal end the egg is broadly capped with uniform dark 
brown. 
Incubation. Complete period not determined. Dr. Needham found a 
cluster June 13. It began hatching the 23rd. 
Hatching. Dr. Needham secured a splendid photograph of the little 
bug emerging from the shell. They came out of the egg by lifting a de- 
tachable cap of the shell. ‘“The embryo lies once folded within the shell, 
its head flexed upon its breast, and its beak and legs extended flat against 
the venter of the abdomen. Thus the dorsum of the prothorax abuts 
against the detachable crescentic groove. The eyes appear before hatch- 
ing as black spots upon the arms of this crescent. The back is almost 
invariably downward, as seen in the figure, though sometimes turned a 
little to one side. On account of the obliquity of the pale crescent and 
the constant position of the embryo in relation to it, these eggs might 
readily be oriented for section cutting in embryology.” 
“The thin lateral margins of the abdomen unrolling at hatching, and 
the legs becoming extended, the fledgling at once assumes proportions 
seemingly wholly incompatible with the size of the egg from which it 
came. 
Family NEPIDZ Latr. 1802. 
Latreille, Hist. Nat. Crust. Jns., III, p. 252 (Neparie). 
A. TAXONOMY OF NEPIDA. 
Family Characteristics. Interesting water bugs, distinguished from 
all others by the presence of long, slender caudal filaments which are 
not retractile. The fore legs are raptorial. The middle and hind legs 
very little adapted for swimming. The tarsi are 1-segmented. The beak 
is short and 3-segmented. The antenn# are concealed and ocelli are 
absent. The wings are reticulately veined. 
Three genera in America north of Mexico, Nepa, Curicta, and Ranatra. 
Only the last genus named is credited with more than one species. It is 
given seven by Van Duzee. 
Historical Review. These strange-appearing bugs were among the 
first aquatics to be noted in the literature. Frisch, 1727, describes and 
figures both a Nepa and a Ranatra under the following names: 
“Von der breiten Wasser Wanze mit den zwen Fang-Klauen und der 
hintern Lufftrohre” and “Von der grossen schmalen Wasser-Wanze mit 
der Fang fussen und der hintern lufftrohre.” This author says that 
Johnston and France Rhedi had mentioned these bugs. Swammerdam 
