Doering: Lei'YRonia quadkangularis. 531 



segment of the abdomen as being the responsible machinery. Since 

 these are the terminal plates, they naturally are the most prom- 

 inent and mider low magnification appear to do most of the work. 

 From a translation of Sulc's work, it seems that he does not attrib- 

 ute the bubbles to the work of merely the last pair of plates, but 

 to all nine pairs, which come together and form the air channel. He 

 thus makes respiration and bubble-formation a simultaneous action. 

 From observations of Lepyronia he is apparently right, since the 

 writer has seen six pairs of plates in action very distinctly. 



COMPOSITION OF THE FROTH. 



The composition of the froth of spittle insects has been studied 

 by different writers. They all have noted the viscid quality of the 

 fluid, which they assert is necessary to maintain the frothy condition. 

 Morse (1900) found that v/hen nymphs were placed in water they 

 immediately began clutching the air and making bubbles. The 

 bubbles disappeared, however, as soon as made, for the clear water 

 did not preserve them. Besides this viscidity, the spittle has a cer- 

 tain insolubility in water and alcohol. When collecting immediately 

 after showers and heavy rains the spittle masses are found intact, 

 even those which were in exposed places. In alcohol the spittle 

 seems to coagulate in a stringy mass, which clings to the feet and 

 body and is hard to pull away. Garman (1921) says that it is 

 readily soluble in sodium hydroxide, has no reaction to iodine, al- 

 though probably containing some sugar, and that the albuminous 

 substance is not coagulated with heat. Gruner (1900) after several 

 experiments comes to the conclusion that 94.565 per cent of the 

 spittle fluid is water, 3.827 per cent organic substance, and 1.607 per 

 cent inorganic salts. The spittle mass of Lepyronia can easily be 

 told in the field from that of a Clastoptera by its composition. The 

 spittle of the former contains more and larger bubbles and resembles 

 the beaten white of egg, while the spittle of Clastoptera contains 

 much smaller bubbles, which seem to be all on the outside of the 

 mass, while the center of the mass appears to be a clear, gelatinous 

 material. Kershaw (1914) states that the spittle of the nymph 

 appears to be a mucin or mucinoid. He found that it granulates 

 with subacetate of lead and stains deeply with methylene blue in 

 glycerin and alcohol. Furthermore, the fluid appears to have every 

 substance excreted from the anus, such as calcium oxalate, uric acid, 

 leucine pellates and urates, potassium and sodium chlorides. 



