INTSODUCTION". 



XXXI 



while on the underside these segments are distinguished by the 

 names of prosternum, mesosternum, and metasternum, together 

 being entitled the sternum, the sides of which are known as the 

 pleurae. The pronotum is always very large, and is more or less 

 the whole of the thorax which is clearly seen above ; the pro- 

 sternum is the origin of the anterior legs. The mesonotum 

 appears above in the scutellum, which is always well developed, 

 and in some instances (Plataspininoe and Scatellerinfe) is of great 

 size, completely covering the abdomen and concealing all traces of 

 wings ; from the sides of the mesothorax issue the anterior wings 

 or hemelytra, while beneath the mesosternum is the origin of the 

 intermediate legs. The metanotum is not visible when the wings 

 are unexpanded ; from the sides of the metathorax issue the 

 posterior or true wings, and the posterior legs originate from the 

 underside or metasternum. On each side of the metasternum 



Fig. 4. — Wings of Catacanthus incarnatus. 



A. Anterior wing or hemelytron. 



a. Coriuui. 



b. Clavus. 



c. Membrane. 



B. Posterior or true wing. 



Lateral margin of corium. 

 Inner angle of corium. 

 Apical angle of corium. 



and near the posterior coxae may be seen the odoriferous apertures 

 or " stink-glands," sacs from which the peculiar odour arises, so 

 well known as appertaining to these insects. These glands are, 

 as a rule, present in the plant-feeding species, but in some of the 

 carnivorous forms (Eeduviidfe, Nepidte, Notonectida^) they are 

 entirely absent, at least as a metasternal apparatus. The smell is 

 not always offensive ; it has been described as resembling that of 

 well-ripened pears or bananas, or that of a fine bergamot pear, 

 or a sweetish smell like ether. In many species it is, however, 

 of a distinctly disagreeable character. These orifices are of 

 considerable classificatory value, especially in a generic sense, but 

 up to the present time their taxonomical value has scarcely been 



