Biology of the Membkacidae of the Cayuga Lake Basin 311 



of peculiar scleritic structure thus suggested is not fulfilled, however, 

 when the anatomy is studied. Aside from the unusual and oftentimes 

 grotesque enlargement of the prothoracic tergum, the general arrange- 

 ment of the skeletal parts is comparatively simple and rather easily 

 determined. 



The prothorax is very weakly attached to the mesothorax and separates 

 from this segment easily. The mesothorax and the metathorax are firmly 

 joined and the sclerites occasionally overlap in such a fashion as to strongly 

 unite these last two segments. 



On the whole the tergum of each thoracic segment is broad, smooth, 

 and, with the exception of the pronotum, simple. The pleuron is narrow, 

 irregular, and more or less complicated, the sclerites are inclined to be 

 twisted from a normal position. The sternum is broad, much sculptured, 

 and indistinctly sutured. 



the prothorax 



No evidence of cervical sclerites has been found. The only suggestion 

 of such structures is a slight thickening of the connecting membrane in 

 the gular region, which in certain species is of sufficient size to warrant 

 attention. On the whole the membranous connection between head and 

 prothorax is remarkably thin and easily ruptured, and shows nothing 

 that could be considered as intersegmentalia or could represent the micro- 

 thorax of Verhoeff (1902). 



The notum of the prothorax shows so much variation thruout the 

 family that no general discussion of it can be attempted. The peculiarities 

 of this region represent by far the most striking and easil}^ recognized 

 characters of the Alembracidae. 



This part of the prothorax is usually expanded into a more or less 

 irregular plate, which covers the entire meso- and metanotum, often the 

 entire thorax, and in some cases the abdomen as well, and bears on its 

 sm'face a wide variety of processes extending to form most grotesque and 

 bizarre structures. A discussion of such variations would be merely 

 an endless catalog, and is of course not to be attempted. Apparently 

 the pronotal structures have no anatomical significance and are merely 

 hollow extensions of the chitinized wall, raised high above the basal 

 membrane which represents the normal body outline. An attempt to 

 explain the function of this structm'e leads at once into the realm of 



