XXIV INSECTA : HYMENOPTERA 367 



leg there projects from the fourth segment a longer, 

 stouter prong, which is used in digging the pollen out of 

 the "pollen-basket" (see p. 373), and also for preening the 

 wings. The back legs are the most complex (see Fig. 292, G). 

 On each there is, on the outer, upper side of the fourth 

 joint, a deep depression fringed round with stiff hairs ; this 

 is known as the " pollen-basket," for in it the pollen obtained 

 from flowers is carried home to the hive. The pollen is first 

 collected on the hairs which cover the body, and then brushed 

 into the baskets by the hairy legs, and especially by the en- 

 larged joint below each " basket " which is beset with rows 

 of stiff hairs, and is used in brushing the pollen off the body 

 into the basket of the opposite side. 

 The " Ab- '^^^ gaster is segmented, five segments being 

 domen " or usually distinguishable. Situated at its free tip 

 Gaster, and is the sting, a complicated and perfect piece of 

 mg. mechanism, by which the skin of the victim is 

 pierced, and poison injected into the wound (Fig. 293). The 

 central part of the sting consists of three special structures, a 

 pair of slender pointed lancets, or " darts," barbed at the tip, 

 and a central, deeply grooved piece, called the director or guide, 

 also finely pointed and barbed at the end. The darts lie in the 

 concavity of the guide, being fixed to it by a sliding junction 

 consisting of two headings running along within the guide- 

 groove, one on each side, each of these fitting into a groove in 

 one of the darts. The darts can be slid along, so that their 

 tips project beyond the end of the guide. These three dark- 

 coloured, piercing organs are enclosed between a pair of fleshy 

 structures, the " sting-palps." Connected with the base of the 

 sting is a poison-gland, and when the sting is being used, this 

 poison is forced down a tubular cavity between the " darts " 

 and the " guide," and entering the wound made by them may 

 cause pain, though the susceptibility of people to the poison 

 varies a good deal ; also after a certain number of stings have 

 been endured the poison usually ceases to have any ill-effects. 

 Sometimes, when a bee stings, it presses the lancets only 

 a little way into the flesh, and if left undisturbed it can then 

 withdraw them, but if they are pressed right in as far as they 

 will go and then an attempt is made by the bee to hastily 

 withdraw them, the whole sting usually becomes separated 

 from its body ; in this case, the insect dies soon afterwards. 



