148 Journal New York Entomological Society. [Vol xin. 



being also the best way of packing them for transportation. To soften 

 them, they can be put with perfect safety into a little cold water, and 

 in the course of an hour or so they will be sufficiently relaxed to be 

 pinned without danger of breaking off legs, etc. 



Living Notonecta for breeding or study should be put in a clean, 

 dry tin box with a little excelsior in it to give them something to cling 

 to, so they may not be too much shaken about or huddled together, 

 which wets them and seems to be otherwise hurtful to them. It is 

 wise also to put in with them a small piece or two of moist water- 

 weed, which seems to help to preserve them in good condition till the 

 aquaria can be-reached. When in captivity, they should be fed on 

 living flies or other small insects, which can be dropped into the water 

 near them. One or two flies a day apiece appear to be enough to keep 

 them in good condition. 



In preparing the list of distribution I have consulted the papers 

 indicated in the appended bibliography, and they will be denoted by 

 the number each title bears in this list, which follows each locality. 

 Other sources will be denoted by name. 



The genus Notonecta is peculiar for the lack of a sufficiency of fixed 

 diagnostic characters to facilitate the separation of the species by 

 means of tables. Color is unreliable to a degree, varying as it does 

 with locality, age, condition, or even without any assignable cause in 

 the same species. For instance, the general coloration of Notonecta 

 undulata Say, our most common and widespread species, varies from 

 pure white with yellow scutellum, greenish feet and claret-colored 

 eyes, to an entire black color, the feet and eyes remaining the same, 

 and the scutellum being also black, with gradual and almost imper- 

 ceptible intergrades from one to the other form. Occasionally, N 

 variabilis Fieber is found with black fasciae corresponding to those of 

 N. undulata, to such a degree that it may be taken for a dwarf form 

 of the latter. In view of this, Kirkaldy has proposed as a diagnostic 

 characteristic the proportion of the distance between the eyes at the 

 front, which he has called the vertex, to the distance between the 

 eyes at the base of the head, at the most constricted part, which he 

 has denoted by the term synthlipsis. In practice, and I have made 

 hundreds of measurements, 1 have found this proportion to hold good 

 in each species within very narrow limits of variation ; and in connec- 

 tion with the length of the insect and the proportional length and 

 breadth of the pronotum and scutellum, it affords an excellent means 



