528 The University Science Bulletin. 



was exuded from the arms of the little nymphs. This viewpoint was 

 summarized by Harris (1862) as follows: "Here may be arranged 

 the singular insects called froghoppers, Cercopidse, which pass their 

 whole lives on plants, on the stems of which their eggs are laid in 

 the autumn. The following summer they are hatched and the young 

 immediately perforate the bark with their beaks and begin to im- 

 bibe the sap. They take in such quantities of this that it oozes out 

 of their bodies continually in the form of little bubbles, which soon 

 completely cover up the insects." 



In 1900 several papers on froth formation were published by 

 European and American writers. Morse (1900) is generally given 

 the credit for discovering that the insect emits a liquid only and 

 later enfolds air bubbles in the liquid. His original account really 

 appeared in 1875 in his "Elementary Zoology." Fabre (1900), 

 Gruner (1900), and Sulc (1900) concluded the same thing, but they 

 all differ as to the method by which the result is obtained. 



According to Morse (1900) a clear fluid is emitted by the nymph, 

 which flows over the entire body and fills up the crevices between 

 the legs. Next the insect extends the abdomen out of the fluid, 

 opens the posterior segments like claspers, grasps a bubble of air, 

 and then turns the abdomen under the fluid, allowing the inclosed 

 air to escape. According to him, the movements go on at the rate 

 of seventy to eighty times a minute and thirty to forty bubbles 

 were made in a half hour. He says that the claspers seem to be the 

 tergal portions of the ninth segment. 



Fabre (1900) describes a similar apparatus. According to him, 

 the insect has a special device, which is composed- of the two pleural 

 lobes of the ninth segment, acting as claspers for grasping air, and 

 a pocket, formed by these lobes, which serves as a container for 

 air. From a caudal view of the abdomen, when the two pleural 

 lobes are drawn apart, a y-shaped opening in the pocket is produced, 

 or, in other words, the expanding and contracting of these lobes 

 opens and closes the pocket. In producing the bubbles the tip of the 

 abdomen is thrust out of the liquid, the pleural lobes spread apart, 

 letting air into the pocket, then close together again, and at the 

 same time the abdomen is pulled under the fluid. At this point the 

 pocket, being flexible, contracts, and thus forces air out of the 

 pocket, forming a bubble in the viscid fluid. 



The explanation of bubble formation advanced by Gruner (1900) 

 is similar to that of Fabre's in that he too describes a pocketlike 

 cavity and two terminal clasping plates. He maintains, however, 



