172 



TEXT-BOOK OF ENTOMOLOGY 



semipupa, the end of the abdomen decreases in size, and is gradually 

 incurved toward the base (Fig. 193), and the three pairs of append- 

 ages approach each other so closely that the two outer ones com- 

 pletely ensheath the inner pair, until a complete extensible tube is 

 formed, which, by the changes in form of the muscles within, is 

 gradually withdrawn entirely within the body. 



An excellent account of the honey-bee's sting is given by Cheshire (Figs. 194, 

 195) . The outermost of the three pairs of stylets forming the apparatus is the 



two thick, hairy "palpi" 

 or feelers (P), these being 

 freer from the sting proper 

 than in the ovipositor of 

 Orthoptera. The sting 

 itself is composed of the 

 two inner pairs of stylets ; 

 one of these pairs is united 

 to form the sheath (sh), 

 while the other pair form 

 the two barbed darts. The 

 sheath has three uses : first, 

 to open the wound ; second, 

 to act as an intermediate 

 conduit for the poison ; and 

 third, to hold in accurate 

 position the long barbed 

 darts. The sheath does 

 not enclose the darts as a 

 scabbard, but is cleft down 

 the side presented in Fig. 

 194, which is below when 

 the sting points backward. 

 But, says Cheshire, as the 

 darts move up and down, 

 they would immediately 

 slip from their position, 

 unless prevented by a 

 mechanical device, ex- 

 hibited by E and 6 Y , giving 

 in cross-section sheath and 

 darts near the end, and at 

 the middle of the former. " The darts (d) are each grooved through their entire 

 length, while upon the sheath (sft) are fixed two guide rails, each like a prolonged 

 dovetail, which, fitted into the groove, permits of no other movement than that 

 directly up and down." The darts are terminated by ten barbs of ugly form 

 (Z>, Fig. 194) , and much larger than those of the sheath, and as soon as the latter 

 has established a hold, first one dart and then the other is driven forward by 

 successive blows. These in turn are followed by the sheath, when the darts 

 again more deeply plunge, until the murderous little tool is buried to the hilt. 

 But these movements are the result of a muscular apparatus yet to be examined, 

 and which has been dissected away to bring the rigid pieces into view. The 

 dovetail guides of the sheath are continued far above its bulbous portion, as we 



FIG. 191. A, end of larva of Encyrtus of 2d stage, show- 

 ing- the three pairs of iinaginal buds of the ovipositor g 1 , q", <; 3 . 

 B, the same in an older larva ready to transform ; i, intestine ; 

 a?, genital gland ; a, anus. After Bugnion. 



