ON STRUCTURE 135 



propodeum has no appendages. The mesothorax 

 above has two parts, a larger portion in front called 

 by some the scutum (6 2 ), and a smaller portion be- 

 hind called the scutellum (& 3 ). These are separated 

 from each other by a transverse impression, and 

 the scutellum is often raised into a sort of little 

 shield ; behind this is another little elevation 

 called the post-scutellum (6 4 ) ; this is really the 

 dorsal apex of the metathorax, and behind this 

 lies the propodeum (6 5 ). Each leg is composed of 

 various parts, and articulates into a cavity of the 

 thorax called the acetabulum. The first two joints 

 of the leg, the coxa (d 1 ) and the trochanter (d 2 ), are 

 very short ; then follows the femur or thigh (d s ) ; 

 then the tibia or shin (d*) ; and finally the tarsi (d 5 ), 

 which compose the foot. At the apex of the tibia 

 are usually two spines called the calcaria (d & ). The 

 tarsi are five-jointed, the joints following each 

 other in a linear arrangement, and in the Anthophila 

 the basal joint is more or less dilated ; the apical 

 joint bears two claws (unguiculi, d 1 ) which are 

 sometimes toothed, and between them, in some 

 genera, there is what is called a pulvillus (d 8 ) or 

 cushion ; this is very large and dilated in some 

 of the fossors. 



