6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, I46 



form characteristic lines on the head; on the thorax the pleuron is 

 braced between the wings and the legs of the wing-bearing segments 

 by a strong ridge- forming sulcus. Elsewhere, all over the body, simi- 

 lar reinforcing grooves may be present. They differentiate the cutic- 

 ula into areas known as sclerites, and have given the impression 

 that the insect skeleton is composed of plates united along "sutures." 



Body regions and plates: In describing the surface regions of 

 the body or those of a body segment, we have in general three areas 

 to distinguish and in each segment three corresponding sclerotiza- 

 tions. To name these we have a choice of both Latin and Greek 

 names for the body surface regions of an animal but no names for 

 the segmental plates on the insects. Hence the available names have 

 been used arbitrarily to fit the needs of insect anatomy without strict 

 regard to the primary meaning of the words. 



The entire back of the insect or the back of any segment may be 

 called the dorsum (L. for back), and from this we have the term 

 dorsal. The back plate of a segment may then be given the name 

 tergum, another Latin word for back. In the thorax, however, the 

 Greek name notum is preferable in order to combine properly with 

 the Greek prefixes pro-, meso- and meta- which designate the 

 segments. 



For the sides of the animal we have no technical term in common 

 use. Since, however, lateral refers to direction toward the side, it is 

 to be assumed that the side itself is the Latin latus. Lateral sclero- 

 tizations of the segments, when not a part of the dorsal or ventral 

 plates, are termed the pleura (Gr. pleuron, a rib), and the pleural 

 sclerites are properly plettrites. 



The whole underside of the animal is appropriately the ventral 

 surface from the Latin word venter. The Latin word, however, 

 meant specifically the belly (also the stomach or the abdominal 

 cavity). A segmental sclerotization of the venter is a sternum (Gr. 

 sternon, the breast or chest), whence sternutation or sneezing. 



The segmental tergal and sternal plates are often called "tergites" 

 and "sternites." The suffix ite, however, means "a part of" in 

 anatomy, as in somite or podite. It is therefore incongruous to apply 

 ite terms to whole plates, and, worse, it leaves us with no terms for 

 parts of the terga and sterna when the latter are subdivided into 

 true tergites and sternites. (It should be noted that tergite is pro- 

 perly pronounced in English as ter'-jite.) 



Tergum and notum: Tergum is Latin for the back of men or 

 animals, but, since we have also the Latin word dorsum for the whole 



