208 Journal New York Entomological Society. [^'°'- xxiv, 



surface whose irregular surrounding edge is well raised above the 

 plane of the segment and bears two teeth at its lower extremity. 

 The tibial scale is also present in the male but is very small and barely 

 perceptible. The coxae are large, subcylindrical and closely articu- 

 lated with the body. The trochanters are small at their base but 

 increase in size at their distal ends ; they arise dorso-apically from 

 the coxse. All the femora are large and are stoutest at the base, 

 tapering toward the outer end. The tibiae are shorter than the 

 femora and are rather uniform in size throughout; their inner sur- 

 faces are flattened or even concave. The tarsi are composed of five 

 segments, the first being much longer than the other four together. 

 The last segment bears a pair of curved bi-cleft claws between which 

 is a pulvillus. 



All the segments of the legs bear more or less hair, though it is 

 longest and densest on the femur, tibia and first joint of the tarsus. 

 The hind tibiae and tarsi of the females are especially well adapted 

 for collecting pollen because of their very long, dense hairs. 



Secondary Sexual Distinctions. 



There are several sexual distinctions, besides the copulatory arma- 

 ture in the males and the sting in the females, as follows : 



1. The antennae of the female have twelve segments, while the 

 antennae of the male have thirteen. 



2. The posterior tibia in the female has two spines, while in the 

 male there is only one present. 



3. The female has six exposed abdominal segments, while the 

 male has seven above. 



4. There is a triangular row of spines on the dorsal side of the 

 last abdominal segment in the female, not present in the male. 



5. The mandibles of the male are always two-toothed and more 

 narrowed than in the female. 



6. The frons of the male of many species is yellow while that of 

 the female is always dark. 



7. The males of some species are entirely yellow while the females 

 are dark. 



8. The tibial scale is very large and prominent in the female 

 while it is barely perceptible in the male. 



