124 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



colorino-, ))ceau,se a short time is required, in several species which have 

 been observed at least, after the emergence of the adult from the pupal 

 stage before the full depth of coloring is acquired. There is, however, 

 a common variation in color, apparently not due to difference in age, 

 producing in some of the most variable species color varieties. These 

 ma}' be either lighter or darker than the color of the typical form, but, 

 so far as our observations have gone, complete intergrades are to be 



found. 



A variation from the usual number of segments in the antennae is 

 quite fre<|uently met with, but this is alwa3^s in the line of a reduction 

 in numlier du(^ usually to a fusion of the last two or more segments. 



The length and breadth of the abdomen is, perhaps, the most variable 

 character, as in most species the segments are slightly telescoped natur- 

 ally, and being connected with each other by a flexible membrane are 

 capable of great distension. This may be caused naturally by the simul- 

 taneous development of a number of eggs in the ovaries of a female. 

 When specimens are mounted in balsam, glycerin, or any such medium 

 for study, there is danger of compressing the body of the insect if 

 care be not taken to have present plenty of the mounting medium, and 

 the usual result of this compression is the distension of the abdomen. 



Measurements of a series of specimens show that a variation, often 

 amounting to one-sixth, sometimes as- high as one-fourth, frequently 

 occurs between the extremes in the size of individuals in the same 

 species. 



SYNOPSIS OF SUBORDERS AND FAMILIES. 



Female with a saw-like ovipositor. Terminal segment of abdomen of female 

 conical; that of males rarely like females, but usually bluntly rounded. Fore 

 wings witli at least one longitudinal vein reaching from base to tip of wing. 



Terebrantia (p. 124'). 2 



Female without an ovipositor. Terminal segment tubular in both sexes. Both 

 pairs of wings similar in structure with only one median longitudinal vein, and 

 this only partially developed, never reaching to tip of wing. .Tubulifera (p. 187) . 

 Includes single family Phloeothripida'. 



'Antenna; with nine segments. Wings broad and rounded at the tips; fore wings 



with cross veins. Ovipositor of female up-curved ^olothripid^ (p. 126). 



Antennse with six to eight segments. Wings usually narrow and pointed at tips, 

 without cross veins. Ovipositor of f emale down-curved. .Thripidjs (p. 132). 



CHARACTERS OF TEREBRANTIA. 



Antenna?, have from six to nine segments, the terminal segments 

 being usually much smaller than the preceding. Ocelli absent in the 

 entirely wingless forms {AjAmothrlps rufus) as in all wingless Thysa- 

 noi)tera, and sometimes in the wingless males of species in which the 

 females are winged, they are present in all long winged forms. Maxil- 

 lary palpi usually three, sometimes two segmented, and labial palpi 

 usually two, sometimes four segmented. 



2- 



