THE WHERRYMEN OR WATER STRIDERS. 975 



near middle behind which they are widely depressed. Elytra usually 

 entire, almost reaching tip of abdomen. Other characters as in key. 

 Length, 9 — 11 mm. 



Common in Indiana, especially so on the lakes of the north- 

 ern counties. Occurs throughout the year, hibernating beneath 

 logs and other cover, usually close to water, but occasionally 

 taken in winter and in times of drought on woodland slopes a 

 mile or more distant from any stream. Ranges from Quebec 

 and New England west to the Pacific and south to North Caro- 

 lina, Georgia and Texas. It is apparently more at home on 

 ponds and in the bays of lakes than on streams, but is usually 

 common wherever found. The elytra are rarely absent, but 

 occasionally reach only to middle of abdomen. When kept in 

 captivity by Riley, its feeding habits were the same as those 

 of remigis but, being a much smaller form, it was more hesitant 

 about attacking the larger living insects which were furnished 

 them. He also has recorded (1922) that marginatus practices 

 cannibalism during periods of stress or of great scarcity of 

 food, as in severe drought. 



1110 ( — ). Gerris insperatus Drake & Hottes, 1925a, 71. 



"Very similar to marginatus. Color markings, form and size the 

 same. Connexiva, except outer margins, and median portion and poste- 

 rior margin of last ventral, golden yellow; median stripe of venter vary- 

 ing from golden yellow to brown. Macropterous form only known. The 

 notch of the last segment of venter and plump genital segments without 

 a keel distinguish the males from those of marginatus. The females of 

 the two are hard to separate. Length, 7.4 — 8.6 mm." 



Knox Co., Ind., July 5 (W.S.B.). Homer, 111., April 27 

 (///. Nat. Hist. Surv. Coll.). Ranges from Ottawa, Ontario, and 

 New York west to Ohio and Illinois and south to Mexico. 



1111 ( — ). Gerris alacris Hussey, 1921, 11. 



In addition to characters mentioned in key, this form differs from 

 marginatus in having the abdomen dull yellow margined with blackish, 

 or rarely wholly blackish; median carina of pronotum less evident; elytra 

 usually abbreviated, reaching middle of third dorsal. Male with sides 

 of median emargination of sixth ventral somewhat more parallel; female 

 with genital segment more narrowed apically and spines of sixth ventral 

 more blunt. Length, 7 — 10 mm. 



Clark Junction, Lake Co., Ind., July 4 {Gerhard). The types 

 were from a small pond at the foot of a sand dune on the shore 

 of Lake Michigan in Berrien Co., Mich., and it is known only 

 from similar ponds in the dune region and at Ann Arbor. 



