HENRY SKINNER 197 



I mention this search trusting that caUing attention to the 

 matter will result in eventually finding the types. These species 

 cannot be disregarded on the ground that they were described 

 solely from the genitalia. There is no doubt whatever, that in a 

 number of species,the genitalic characters are far more positive 

 as a means of differentiation than the color and maculation. My 

 own studies have shown that the individual variation in the geni- 

 talia is slight and that some species looking very much alike in 

 color and markings have totally different genitalic structure. This 

 is illustrated by icelus and brizo and juvenalis and hor alius. Tristis 

 and cUtus also are very much alike in appearance yet totally dif- 

 ferent genitalically. Two species have been confused for years 

 under the name pacuvius, yet they are very readily separated by 

 differences in the sexual characters. 



The method I have adopted for the study of the genitalia is a 

 very simple one. The latter half of the abdomen is broken off 

 and boiled for about two minutes in a ten per cent water solution 

 of potassium hydrate (caustic potash). The genitalia are dis- 

 sected out under water, by the aid of needles mounted in wooden 

 handles. The parts are then put in 95 per cent alcohol and left 

 there for at least an hour. They are then dried on a blotter, put on 

 an ordinary glass slide moistened with xylol and mounted in balsam 

 damar in benzole with the ordinary cover glass over the mount. 



I have found the structure of the clasps or harpes quite sufficient, 

 as differential characters, but have also studied the other parts 

 (''upper organ" and penis) as well and have found them useful 

 for the confirmatory evidence. The structure of the genitalia 

 makes it difficult to mount the whole organ intact without distor- 

 tion, or the possibility of having a different view in each specimen. 

 I have therefore, wherever I found it necessary or expedient 

 mounted the various parts separately on the slide. More than 

 one hundred slides have been made and they have all been num- 

 bered to correspond with the pin numbers on the insects. 



Interesting genitalic studies of some of our species were made by 

 Godman and Salvin and illustrated in the Biologia Centrali Ameri- 

 cana and their work was a step in advance. Dr. H. G. Dyar 

 gives a synopsis of the species both from the maculation and geni- 

 tafic standpoints.^ Mabille in the Genera Insectorum , Hesperidae, 



« Joum. New York Ent. Soc, xiii, 120 to 122, 1905. 



TRANS. AM. ENT. SOC, XL. 



