VIII INTRODUCTION 



cheek is used for the space between the eye and the base of the 

 mandible (''malar space" of Smith and Shenefelt). temple is used 

 for the space between the hind margin of the eye and the occipital 

 carina ("gena" of Smith and Shenefelt). clasper is the outer lateral 

 piece of the male genitalia ("paramere" of Smith and Shenefelt). 

 The epipleurum (not in the Smith and Shenefelt diagrams) is the 

 thin free flange attached to the lower margin of an abdominal tergite 

 and usually sharply turned mesad to cover part of the lower side of 

 the abdomen laterally. The orbit is the part of the head next to the 

 eye. The orbit is divisible into regions, with self-explanatory termi- 

 nology, like frontal orbit, hind orbit, lower hind orbit, etc. 



The spelling pleurum, rather than pleuron, is preferred in this paper. 

 Pleurum comes from the Greek "pleuron", meaning side. It is a 

 word similar to notum and sternum, which come from "noton" and 

 "sternon". All three Greek words have the neuter singular ending 

 "-on", which when brought into English may be transliterated as 

 -on or given as the Latin neuter singular ending -urn. It is strange 

 that "noton" and "sternon" have come to be spelled notum and 

 sternum in English, while the structure between them, coming from a 

 Greek word with the same ending, is more often spelled pleuron than 

 pleurum. Either the -on or the -um ending would be linguistically 

 acceptable for any of the three, but since they are for adjacent struc- 

 tures and are often used together, simplicity suggests that the choice of 

 endings should be the same in all three cases. 



Counts and Measurements 



In counting the abdominal segments, we (like Smith and Shenefelt) 

 start with the first apparent segment rather than with the first 

 morphological segment. The propodeum (the morphological first 

 segment of the abdomen) is included as a part of the thorax, which 

 it is from a functional standpoint. 



Heavy use is made of measurements in the keys and descriptions, 

 not because we are fond of them or because they are unusually con- 

 stant, but because they seem to be the most convenient way to 

 express the differences of relative size and proportion which must be 

 relied on for many distinctions. A multitude of drawings would 

 be the only other practical method for showing these differences. 

 In measurements of proportions, like length in relation to width, 

 we have used a microscope with an ocular micrometer for the measure- 

 ments and a slide rule for the computations. The resulting figures 

 express differences that are evident to the practiced eye when com- 

 parison material is available, and need not be checked by measure- 

 ment in such cases, but without comparison material one must 

 usually measure rather exactly with a microscope and ocular microm- 



