NEPIDJE. 537 



pearance at the beginning of the spring, and the parent sur- 

 vives until they have arrived at maturity." (Westwood.) The 

 recently hatched young are broad, oval and flattened. Noto- 

 necta undulata Say (Fig. 542) and N. irrorata Say are our more 

 common forms. The genus Ploa differs from the preceding, 

 in the fore wings being coriaceous, and "united together by 

 a straight suture." 



Leach. These insects have very flat bodies which 

 are either oval or very long and linear. The head is sunken 

 into the thorax, with large eyes, but no ocelli. The antennae 

 are short, three or four-jointed, and concealed in a cavity under 

 the eyes ; the beak is three-jointed. The fore wings are mem- 

 branous, and the fore feet are raptorial, while the hind limbs 

 are formed for swimming. In Nepa and Ranatra the body 

 terminates in a long breathing tube, and the tracheary system 

 in these two genera is very peculiar, being very largely devel- 

 oped on the under side of the body. There is a large air- 

 bladder within the metathorax, leading from the spiracle, which 

 evidently lightens the insect during its flight. In the abdomen 

 the spiracles are only present on the third to the fifth rings ; 

 they are not, however, simple clefts in the walls of the body 

 but are closed by a sieve-like membrane, so that they perform 

 the function of tracheal gills. (Gerstaecker.) 



The genus Belostoma comprises the most gigantic forms of 

 the suborder, some species being from three to four and a half 

 inches long. The body is oval, elliptical, flattened ; the eyes 

 are large and the second to the fourth antennal joints provided 

 with hook-like expansions. The fore tarsi are two-jointed, with 

 a single claw, and the hinder limbs are broad, flat, and well 

 fringed. The larvae are provided with two claws on the fore 

 tarsi. "The females of some species of Belostomse carry their 

 eggs upon their backs, arranging them in a single layer with 

 great symmetry." (Westwood.) Belostoma Haldimanum Leidy 

 is not uncommon in our waters. It is three inches and a half 

 in length, and has black patches on the under side of the body, 

 while in B. grisea Say, which is of the same size, the under 

 side is unspotted. Professor A. E. Verrill has sent me the 

 eggs and freshly hatched young of one of our New England 



