No. 504] ORIGIN OF FROTH IN SPITTLE-INSECTS 785 



by Poupart (1705), Friseh (1720), GeofTroy (1764), De- 

 Geer (1773) and others. Morse (1900) modified this 

 view somewhat in that he gives as his opinion that what 

 comes out of the anus is a " clear somewhat viscid fluid " 

 and that by means of appendages at the extreme tip of its 

 abdomen the insect secured a moiety of air by grasping it, 

 so to speak, and then instantly releasing it as a bubble 

 into the fluid. Gruner (1900 and 1901) states that the 

 fluid is exuded from the anus and passes under the body, 

 flowing into a pocket-like space where it becomes im- 

 pregnated with air which comes out of the stigmata 

 located in the pocket. 



Porta (1900 and 1901) believed that there were open- 

 ings on the dorsum of Aphrophora which were connected 

 with oval glands little distinct from the hypodermis. He 

 describes them as arranged at the base of the excretory 

 canal in numbers of five, six or even fewer, indistinctly 

 separated from one another. To these glands he ascribed 

 the function of producing the fluid. He also states that 

 the bubbles are blown into the fluid by the method de- 

 scribed by Morse. 



Girault (1904) states that " during the process of se- 

 cretion the fluid flows slowly from a point near the anal 

 opening, and gathers between the legs, where, by their 

 alternate agitation, it becomes mechanically mixed with 

 air and forms cushions of air bubbles," and he further 

 states ' ' that the air is taken in at each up and down mo- 

 tion of the abdomen and that during this dipping proc- 

 ess the ventral plates are in transverse motion like jaws, 

 and that it is probable that the secretory glands are be- 

 tween them. ' ' From this we should infer that he thought 

 that it came from special secretory glands and not from 

 the anus. 



Berlese (1907) believes that the froth is secreted by 

 glands found upon the seventh and eighth abdominal 

 segments, previously described by Batelli (1891). 



In the following it is proposed to discuss the evidences 

 bearing upon each of the current views presented above 



