94 HYMENOPTERA. 



each case, and then refer to the existing variations in the 

 discussion. By this means the typical forms can usually be 

 separated, from a study of which the rest may more easily 

 be grouped. 



The following is a list of characters that have at some 

 time been used, and a brief statement of their values in classi- 

 fication : 



Size. — Quite variable in both sexes, and only of use in connection with 

 other characters. 



Wings. — Venation, shade, and yellow ^ spot at base all variable and 

 useless. 



Legs. — Size and shape uniform and furnishing no characters ; mark- 

 ings of comparatively little .value. 



Antennce. — Color useless, except when on scape, and then of only 

 secondary importance ; size and form of the scape useful in 

 the males. 



Thorax. — Markings on collar and tubercles of value ivheii constant; 

 but often not constant ; other marks useless ; puncturation 

 valuable within moderate limits, but not absolutely constant 

 in any species ; enclosure of propodeum likewise variable, 

 and not certain. 



Abdomen. — Shape and puncturation valuable in both sexes if distinct, 

 otherwise not. 



Head. — Puncturation quite useful, especially that of occiput ; propor- 

 tions, position of antennal sockets, etc., valuable in both 

 sexes, except in a few cases ; markings valuable in the male 

 when constant ; less so in the female ; shade of markings 

 valueless. 



Genitalia. — Very valuable in the male, especially seventh and eighth 

 ventral plates. 



A word about the collecting and handling of specimens 

 might well be added at this point. First of all it is essential 

 that large series be collected, if valuable work is to be done. 

 Next in importance is full and accurate data, for it is only 

 by such means that the range, habitat, and time of appear- 

 ance can be learned, or a record of the flowers visited by 

 each species obtained. It will also add to the value and 

 facilitate the study of the specimens if they are glued on 

 cardboard points, instead of being pinned thru the thorax, 

 for the pin distorts the specimen and interferes with the lens 

 in examining it. Especial pains should be taken to get 

 specimens in copula, and preserve them on the same pin, for 



