NO.1310. NORTH AMERICAN THYSANOPTERA— HINDS. 123 



the determination of length and breadth of the species herein 

 described. 



When comparative lengths onl}' are desired, as e. g. in the compara- 

 tive lengths of segments of antenntv, relative length and breadth of the 

 head, etc., there is no need to determine the actual measurement. It 

 is sufficient to compare directly the number of spaces read upon the 

 eyepiece micrometer, and this is the method used in such cases. In 

 the case of the comparative lengths of segments of the antenna\ all 

 measurements have been made with a |-inch ol)jective and a 1-inch eye- 

 piece. The measurements given show, therefore, not only a compari- 

 son between the segments of one antenna, but also between the seg- 

 ments of all antennfe so measured. The number of the segment has 

 been given above the line, and directly below it the number of spaces 

 of the eyepiece micrometer covering that segment. Illustration: 

 Number of segment, 12 3 15 etc. 

 Spaces of micrometer, 5 10 11 12 S) etc. 



It has been found that there are slight individual variations in the 

 lengths of corresponding segments in dilierent specimens of the same 

 species, and even in the two antennte of the same specimen, still there 

 is in general a quite close agreement in this respect and the propor- 

 tions hold very well. The antenn;e were selected for such critical 

 study, because there is an evident variation in the proportional lengths 

 of segments in each species, and because the antennas are the most 

 surely availalile for a careful, accurate study of any organs of the 

 insect. Then, again, proportional measurements do not vary nearly as 

 much as do the absolute measurements of different sized individuals. 



All statements made as to lengths, both actual and comparative, in 

 the descriptions herein given are based upon actual measurements 

 made in one or the other of these ways, an average being taken of the 

 total number of specimens used in the description. 



In describing colors it has been my intention to follow a few definite 

 rules, which are given herewith: First, to name colors in plain, well- 

 known terms when possil)le; second, when the color being descri])ed 

 appears to result from a mixture, in equal proportions, of two more 

 elementary colors, they have been given together in the same form and 

 connected b}' a h3^phen (graj^-brown); third, when a predominant 

 ground color is modified by more or less mixture with another color, 

 the name of the ground color has been given last with the modif^dng 

 color preceding it (gra^'^ish brown). Depth of coloring is indicated by 

 such words as light, dark, etc. 



INDIVIDUAL VARIATIONS. 



Individual variation must always be considered in specific determi- 

 nations and due allowance made therefor. The most common variation 

 will naturally be found in the line of color. It is prol)able that to a 

 slight extent the age of the individual may influence the depth of the 



