Doering: Lepyronia quadrangllaris. 529 



that the air for the bubbles is supplied from the tracheae. The fol- 

 lowing is his account of the process: ''Soon after the larvae have 

 fastened themselves head downward on the plant and have imbibed 

 some of the sap. the terminal portion of the abdomen rythmically 

 contracts so that the fluid from the anus is exuded and flows into the 

 cavity or pocket. The insect being head downward, the fluid flows 

 into the pocket, where it becomes mixed with air coming from the 

 last few pairs of spiracles. Bubbles are thus produced in the pocket 

 by the contraction and expansion of the tergal plates." 



Sulc (1910) describes a still different apparatus, namely the air 

 canal. He says that the "pochette" of Fabre and the "tasche" of 

 Gruner is not present, but that the special device is the air canal 

 (pi. LXII, figs. 6 and 7). This air canal or channel is formed by the 

 tergal pads or plates. Beginning with the fourth segment and ex- 

 tending to the ninth, the plates are prominent and are capable of 

 touching on their median margins. The plates of the first and 

 second segments are short and widely separated from each other 

 The tergal plates of the third abdominal segment are triangular, so 

 that only their posterior medial margins can touch each other. 

 Arising from the median portion of the third sternite between the 

 two plates there appears a special triangular, caudad-projecting 

 protuberance (pi. LXII, fig. 6), which serves to close the channel. 

 Thus the tergal plates form a channel which extends directly from 

 the ninth segment to the rniddle of the third. At this point it be- 

 comes Y-shaped, dividing into two smaller channels, which continue 

 to the right and left until the hind margins of the thorax are reached. 

 When the cercopid is submerged in the spittle the tergal pads are 

 pressed firmly together by means of the contraction of strong 

 muscles, and the tip of the abdomen just reaches the surface of the 

 spittle. According to Sulc, the froghopper nymph can be compared 

 to water-dwelling insects with open, tracheal systems, only devi- 

 ating from all hitherto know^n examples by having this special de- 

 vice of the air channel. When fresh air is desired the tip of the 

 abdomen is thrust out of the spittle, the air channel opens and the 

 air enters. Immediately the air channel is compressed and at this 

 moment a bubble is released in the spittle mass. 



The writer's own observations were made before reading the 

 above descriptions. It was very difficult to view this process at all, 

 because of the difficulty of getting the nymphs to settle on the cut 

 plants, and when they made the foam on living plants it was almost 

 impossible to focus the microscope on them. Most of the observa- 



