AQUATIC INSECTS 



long periods. The aquaria will need screen-covers, for they 

 can fly out of their dishes just as they can from ponds. Only 

 a few should be kept in a dish, for they need space, and a few 

 water plants to make them feel at home. They will eat small 

 water animals of almost any kind; the water boatmen need 

 only some good bottom ooze full of plant tissues. Many 

 water-bugs will lay their eggs and their young will hatch in 

 captivity. 



Identification.— Excellent accounts of all the families of 

 aquatic Hemiptera have been given by H. B. Hungerford in 

 his report "The Biology and Ecology of Aquatic and Semi- 

 aquatic Hemiptera." 



Key to families of aquatic Hemiptera here included, after 

 Hungerford. 



1. Antennae shorter than head. 2 

 Antennas as long as or longer than head, exposed. 6 



2. Hind tarsi with indistinct setiform claws (save in Plea 



which is less than o.i inch long). 3 



Hind tarsi with distinct claws. 4 



3. Head overlapping thorax dorsally. Front tarsi i -seg- 



mented, palaeform. Water boatmen, CorixidcB, p. 239 

 Head inserted in thorax. Front tarsi normal. 



Backs wimmers, NotonectidcB, p. 237 



4. Membrane of hemelytra (front wings) reticulately 



veined. " e 



Membrane of hemelytra without veins. 



Creeping water-bugs, Naucoridce, p. 238 



5. Apical appendages of the abdomen long and slender; 

 tarsi I -segmented. Water scorpions, NepidcE, p. 235 



Apical appendages of the abdomen short and flat, retrac- 

 tile. Giant water-bugs, Belostotnatidcs, p. 232 



6. Head as long as entire thorax; both elongate. 



Water-measurers, Hydrometridd, p. 228 



Head shorter than thorax including scutellum. 7 



227 



