HENRY J. FRANKLIN. 223 



are slightly elevated and somewhat excavated beneath. 

 These lobes are always less developed in the workers of 

 Bombus than they are in queens of the same species (figs. 

 149 and 176). The writer has seen queens of Bombus with 

 the male genitalia, torn from the body of the male, hanging 

 to the bases of their stings, in position for copulation. 

 When thus observed, the male sagittse were always found 

 passing between the lobes on the inner sides of the basal 

 arms of the sheath of the sting above described. It seems 

 evident, therefore, that these lobes have some function in 

 connection with that of the sagittse. They apparently serve 

 to guide the heads of those organs to the mouth of the 

 vagina. For this reason, they are, in this paper, called the 

 genital guides. In general, they are largest and most com- 

 plex in those species which have the sagittse of the male with 

 the largest and most complex heads. 



Male genitalia (figs. 119 and 120). — These organs are as 

 follows : 



1. Two ventral and basal foliaceous slerites, one underlying the 

 other (fig. 32) . These are, in this paper, called the jr/a/Aisg'. Together 

 they make up what Radoszkowski designated as the couvercle genital. 

 They vary greatly in form between different species and are, therefore, 

 of some value in classification. The outer spatha is always the larger 

 (figs. 122 to 126 inclusive and figs. 148, 152, 153 and 155) and always 

 has its anterior margin curved far backward in the middle and usually 

 is entirely without fenestrae. The inner spatha is always roughly tri- 

 angular in outline and always has its anterior margin thickened and 

 extended forward prominently in the middle and usually has at least 

 one fenestra (fig. 128). These spathse always have more or less hair 

 on the apical portions of their outer surfaces. 



2. A single large, dorsal and basal sclerite. This plate is known as 

 the cardo (figs. 71, 119 and 120, C). It forms the entire basal portion 

 of the genitalia on the dorsal side and, in narrow and tapering exten- 

 sions, it reaches down on each side of the venter to over one-half the 

 distance toward the middle line. By its connecting membranes it pro- 

 vides most of the attachment for the genitalia to the rest of the abdo- 

 men. It is smooth and without hair. It is quite constant in form and 

 appears to have no distinctive character of value. 



3. A lateral organ on each side known astheclasper (figs. 71, CL and 

 120, CL). During copulation, these organs include the basal portion 

 of the female stinging apparatus between them. The presence of 

 numerous muscles indicates that muscular effort is put forth in the use 



TRANS. AM. ENT. SCO. , XXXVIII. 



