hungerford: aquatic hemiptera. 161 



swimming forms, chiefly small crustaceans and insects which come near 

 the surface of the water. Like the adults, they are very efficient ene- 

 mies of mosquito larvae. They do not pursue their prey, and seldom 

 catch forms that keep close contact ynth. solid objects. They are like 

 so many traps set and respond to an impact upon the water." He 

 observed one very young bug catch an Ostracod which closed up and 

 escaped. 



Ormerod in the Ento., XI, p. 95, gives the economic side to the foraging 

 of this bug. Record is made of its attack upon the spawn of fish. The 

 only method of ridding the ponds was to drain them dry and restock with 

 fish. Swammerdam's account still stands as a good one. "There is not 

 perhaps in all the animal creation so outrageous or fierce a creature 

 against those weaker than itself than the water scorpion. It destroys, 

 like the wolf among sheep, twenty times as many as its hunger requires. 

 I have often seen one of these when put into a basin of water in which 

 were 30 or 40 of the worms of the middle Libella, which are at least as 

 large as itself, destroy them all in a few minutes." Bueno has found 

 that their food consists of those unwary insects that fall into the water. 

 The writer thinks that much of their food consists of such May-fly 

 njTTiphs * as clamber about in the same environment. These it captures 

 as they swim by. 



Behavior. Holmes and Severin have studied the behavior of these 

 insects. In Holmes' "Evolution of Animal Intelligence" are several notes. 

 He finds it negative to light when first brought to light from the dark, 

 but this soon gives way to a decided positive response. 



Bueno, 1903, published an interesting account of the stridulation of 

 Ranatra. When one of these insects is lifted cut of the water it often 

 gives forth a peculiar squeaking sound. The writer has not found it 

 very loud, and often the bug must be held to the ear to hear it at all. It 

 resembles somewhat the hum of a muddauber wasp at its building. 

 Bueno describes it as a "rasping, creaky chirp." This sound or chirp- 

 ing is made by "holding the fore pair of legs in the same plane as the 

 body, perfectly straight" and separated as far as the prothoracic shoulder 

 will permit and then jerking these rigid limbs up and down. The sound- 

 producing device is figured on plate XVIII. There is, on the inner face 

 of the outer lobe of the prothorax suri'ounding the coxae, a stridular area 

 as figured. A roughened spot on the coxa makes the rasp that completes 

 the musical device. Kiritshenks in Rev. Russe Entom., X, p. 311, men- 

 tions an interesting flight "en masse" of Ranatra linearis. 



DESCRIPTION OF STAGES. 



These are taken from Bueno and relate to Ranatra quadridentata. 



The Egg. 

 Size. 3 mm. long; width, 1 mm.; appendages, 5 mm. 

 Color. White at base, growing dark toward apex; when freshly de- 

 posited, clear white. 



* Callibaetis and Blasturus, for instance. 

 11 — Sci. Bui. — 1669 



