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: HUNGERFORD: AQUATIC HEMIPTERA. 193 
legs may serve as an illustration of this point. In all the instars the 
tarsi end in unequal claws as in the adult, and the tibize possess a 
row of five bristles on their caudo-ventral margin and the tarsi three 
such bristles. 
The metathoracic tarsi end in an unequal pair of claws which are 
prominent in the first instar (plate XX, figure 10), and which become 
Jess and less conspicuous as development proceeds till in the adult 
_ stage their similarity to the other structures of the swimming leg has 
_ led to the common statement that the tarsal claws of hind legs are ab- 
sent in the adult. Upon transforming to the adult stage the 1-segmented 
_ condition of the tarsi is replaced by a 2-segmented tarsus and the 3- 
_ segmented antennze become 4-segmented. (See plate XX, figures 6 
and 7.) 
The eyes occupy an increasingly large proportion of the head in 
successive instars, a point not properly indicated in the drawings which 
were made from living bug's in the water. 
Summary. Notonecta undulata is the most widely distributed of all 
our kackswimmers. It lives well in the aquarium and may be reared 
from deposition of the egg to the adult stage in some forty days if 
placed in isolated jars and given proper attention. The young stages 
_ thrive on a diet of Ostracods and the advanced nymphs do. very well on 
immature and small Corixids for a food supply. In Kansas there are 
;. two main broods in a season, one reaching the adult stage in June, the 
_ other in August. Since these insects draw quite largely in their young 
_ stages upon the Ostracods and similar organisms, which represent a 
_ chief food supply for young fish, as well as preying upon a small fish 
_ directly, as has been noted several times, they deserve more careful 
_ study. This task is greatly facilitated by a workable key to the species 
- and by some knowledge of their feeding habits. 
Biology of Notonecta Variabilis. 
b This species was very abundant in the pools about the Field Station, 
Ithaca, N. Y. The writer has never taken it in Kansas, although it 
should occur there. It likes fresh water, and clings to submerged 
tangles of water plants. 
The Egg. 
The egg is deposited upon a pad of gelatinous material. This 
egg appears to be more truncate at anterior end than the other eggs. 
_ Size Length, 1.69 mm.; width, top view, .65 mm.; width, side view 
: (heighth), .78 mm. 
Color. Surface is hexagonally reticulate; pearly white when first de- 
posited, then turns first amber and then smoky as embryo develops, 
especially at anterior end. Micropyle tube is long and directed toward 
attached side of egg. 
_ Shape. As in other species. 
i First Instav. 
t Size. Length, 2.08 mm.; width of body, .936 mm.; width of head, 
71S mm. 
13—Sci. Bul.—1669. 
