2 PROCEEDINGS OP THE NATIONAL MUSEUM tol. 68 



coloration is rather plain. Numerous species are whitish to yel- 

 lowish without markings, several have dark markings, and only a 

 few show any other colors. 



The scarcity of external features upon which classification might 

 be based suggested appeal to the characters of the genitalia. The 

 aedeagus assumes a remarkable variety of forms, but its structure 

 is very constant for each species. The shape of the eighth sternite 

 of the female also is helpful in segregating species, but is more 

 limited in diversity. 



TECHNIQUE OF GENITALIC STUDY 



Remove the entire abdomen ; this is easily done by applying pres- 

 sure at the base while the specimen is held back down on a cork or 

 other support under a low power of the binocular microscope. The 

 abdomen is more readily severed at the base than elsewhere and 

 usually can be removed without otherwise damaging the specimen. 

 A great advantage in removing the entire abdomen is securing a 

 sizable object to work with; the hypopygium alone is small and 

 more easily lost, and the abdomen makes a convenient handle for it 

 in consequent manipulations. Before proceeding further observe, 

 describe, and draw if necessary, the external features of the genitalia. 

 These are more easily made out in dry than in cleared specimens. 

 For identification all that is necessary in some cases is to flip off 

 (by a forward and lifting pressure with a needle) the anal tube. 

 The apex of the aedeagus often is thus exposed fully enough for 

 its characteristic shape to be observed without further dissection. 

 When it is desired to go further place the specimen in saturated 

 solution of potassium hydroxide in a small beaker or test tube and 

 gradually bring to the boiling point. This is sufficient clearing for 

 most specimens; in fact a litle shorter exposure to the reagent will 

 serve in many cases. A fine needle or pin, hooked and mounted in 

 a handle, is convenient for transferring the specimen to and from 

 the reagent. Upon removal place the cleared abdomen in glycerine, 

 using a slide with a concavity or cell ground in it. Under a mod- 

 erate power of the binocular examine for additional details of ex- 

 ternal structure and add to or amend the notes previously made. 

 This accomplished, tease the hypopygium with fine needles so as to 

 loosen and draw out the aedeagus, but not to disconnect it. These 

 organs are very minute and if separated are likely to be lost; it is 

 well, therefore, to keep them attached to large "handles." Observe 

 the natural relationship of the parts, and describe and draw them 

 in natural positions. Flattening them out under cover glasses is 

 very inadvisable. The genitalia can be studied in a drop of glycerine 

 under powers of the microscope as great as are needed. If high 



