Vol. XXviii] ENTOMOLOGICAL NEWS. 2/5 



in the second instar. Tibia and tarsus of hind leg now fringed with 

 hairs wing pads as in Fig. 4,c, Plate XIX. 



Fourth instar. The middle femora now bear very stout processes in 

 the line of the caudal row of spines. A series of short processes on 

 the ventral side of this segment take the place of minute rugosities of 

 the previous instar. 



Fifth instar. The tooth or strong spine on the mesothoracic tibia is 

 now extremely wide at its base. The limbs are stouter than previously 

 and the wing pads now have the position shown in figure 4e of Plate 

 XIX. 



In the above table the measurements are in millimeters and based on 

 reared material. The adults are certainly smaller than those taken in 

 Ithaca, New York, though practically the same as specimens from na- 

 ture in Kansas. These figures are intended to help in determining an 

 instar. The series measured is not large enough for purposes of gener- 

 alization. 



General notes on development. There are certain constants of struc- 

 ture that are carried through all the nymphal instars. The mesotho- 

 racic 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 tibiae 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 (PI. XIX, fig. 10) and which become less 

 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 absent in 

 the adult. Upon transforming to the adult stage the one-segmented 

 condition of the tarsi is replaced by a two-segmented tarsus and the 

 three-segmented antennae becomes four-segmented. (See PI. XIX, figs. 

 6 and 7.) 



The eyes occupy an increasingly large proportion of the head in suc- 

 cessive instars, a point not properly indicated in the drawings which 

 were made from living bugs in the water. 



SUMMARY. 



Notonccta undulata is the most widely distributed of all our 

 backswimmers. 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 ad- 

 vanced nymphs do very well on immature and small corixids 

 for a food supply. In Kansas there are two main broods in 



