Genus XXVIII.— THEL AXES, Westwood* 



Plattlaus. 



Rostrum long, reaching to the third coxse. Second 

 joint very long and thin, third joint thickened, the 

 last pointed. > 



Antennae rather short, five-articulate, if the nail-like 

 terminal process be not counted. The third joint 

 equal to the two following, taken together. Cornicles 

 wart-like and very short. Wings carried horizontally, 

 and folded one over the other when at rest. Upper 

 wing with a single furcated cubital vein, the other 

 veins as in Pemphigus. Lower wing has only one 

 single oblique vein, springing from the cubitus. 



The eyes in the apterous forms are rudimentary. 

 Kaltenbach points out that they are very small, and 

 that they want the tubercle. 



Von Heyden's genus Vacuna has been so generally 

 received by Continental authors that some may feel 

 regret that any change should be made in the name. 

 However, it now seems granted, as a general rule, and 

 in fairness, that priority in descriptions of genera shall 

 decide between rival names. 



Prof. Westwood by some years has precedence over 

 Von Heyden, and therefore I adopt his nomenclature 

 as above. 



* From 3>jXa£uv, to bear mammae, alluding to the papilliform nec- 

 taries. 



