FIELD BOOK OF INSECTS. 



occasionally go under water; they hibernate and some- 

 times come out in warm winter days to stretch their legs. 

 If you desire to bring home alive for your aquarium 

 species of this and related families, use for the purpose a 

 dry box or one in which there is some damp moss; they 

 frequently drown if carried in a pail containing water. 

 The following key includes the genera most often noticed 

 in our territory. 



1. Body oval, less than 3 times as long as broad; 

 pronotum not longer than broad 2. 



Body elongate, more than 4 times as long as broad; 

 pronotum much longer than broad. Gerris 3. 



2. Second segment of antennas longer than either third 

 or fourth segment M etr abates hesperius. 



Second segment of antennae shorter than either third 

 or fourth segment Trepobates pictus. 



3. Antennae longer than head and pronotum together; 

 hind tibiae and tarsi, together, much longer than middle 

 tibiae. Subgenus Limnoporus, species rufoscutellatus. 



Antennae shorter than head and pronotum together; 

 hind tibiae and tarsi, together, but little longer than middle, 

 tibiae 4. 



4. First segment of antennae nearly the same length as 

 fourth. Subgenus Gerris, of which marginalus is a common 

 species. 



First segment of antennae considerably longer ,than 

 fourth. Subgenus Aquarius, of which remigis is our 

 common species. 



HYDROMETRIDJE 



This family has also been called Limnobatidae and the 

 type, as well as our only, genus is then called Limnobates 

 instead of Ilydrometra (see also Gerridae). The common 

 name is Marsh-treaders. Hydrometra martini (also called 

 lineata] is not rare but is not often seen. It is not quite 

 .5 in. long, very thin, and walks very deliberately over the 

 water and projecting plants. Quoting Uhler again, 

 'They delight to remain at rest, with perhaps a single claw 

 hooked to some projecting object. When disturbed they 

 move very slowly, and seem disposed to save themselves 







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