NO. 2 HONEY BEE — SNODGRASS 'J'J 



individual movement to the tarsomeres, but the entire tarsus is 

 traversed by the flexor-muscle tendon (iiyAp) of the pretarsal 

 claws, and a pull on this tendon causes a deflexion of the slender part 

 of the tarsus beyond the basitarsus. 



The pretarsiis. — The pretarsus of the honey bee has a complex and 

 highly specialized structure (fig. 25 A, B). The median part of the 

 segment is differentiated into a conical, stalklike basal part (E) from 

 which the claws arise laterally, and an oval distal lobe, which is the 

 arolium (Ar). In the ordinary position of the foot (E) the aroHum 

 stands upward between the claws on the end of the basal support. 

 Dorsally the arolium presents a deep concavity (A) between its up- 

 turned lateral parts, and in its outer wall is a dark, elastic, U-shaped 

 band, the arcus (B, E, arc), which embraces the base of the arolium 

 ventrally with its arms extending distally in the lateral walls. The 

 conical base of the pretarsus contains dorsally an elongate median 

 sclerite (A, E, inn) armed with five or six long, thick, curved spines. 

 By its widened base the sclerite is articulated to the end of the tarsus 

 between the bases of the claws, and its narrowed distal end is at- 

 tached like a handle to the base of the scoop-shaped arolium (H), 

 for which reason the sclerite may be termed the aroliar manubrium. 

 In the ventral wall of the pretarsal base is a broad, weakly sclerotized 

 plate, the planta (B, E, pin), thickly beset with strong spines diverging 

 distally. 



The claws are hollow, strongly sclerotized lateral outgrowths of 

 the membranous lateral walls of the pretarsal base. Each claw has 

 two points of unequal length, and in size and shape the claws differ 

 considerably as between the drone (fig. 25 A, B) and the worker (C, 

 D). Dorsally the claws are articulated individually to two small 

 knobs on the end of the tarsus (A, 0, p), corresponding with the ar- 

 ticular condyles at other dicondylic joints of the leg, but the claws 

 themselves are devoid of muscles. 



The motor apparatus both of the claws and of the arolium consists 

 of the depressor muscle of the pretarsus, and of accessory sclerites in 

 the ventral articular membrane at the base of the segment. The prin- 

 cipal one of the basal sclerites is a large median plate, known as the 

 unguitractor plate (fig. 25 B, Utr), which is comparable with the 

 genuflexor plate below the knee joint. In the membrane at the 

 proximal end of the unguitractor plate is attached the tendon of the 

 pretarsal muscle (P5Ap), and at the distal angles are two small 

 auxiliary sclerites (aux) intermediate between the unguitractor plate 

 and the bases of the claws. The pretarsal tendon extends forward 

 through the tarsus (fig. 23 G) into the tibia (fig. 24 K), where it 



