THE PROBLEM OF DEFENCE 169 



its dual function. But in the unsexed or worker classes 

 of social species it has become a weapon pure and simple. 

 Briefly, the sting of a worker hive-bee consists of a grooved 

 and pointed shaft along which slide a pair of many-barbed 

 darts. Externally, there are two feelers or palpi, which 

 are used to ascertain the most vulnerable point of attack. 

 The first thrust is administered by the shaft, which serves 

 to open a wound and to guide the darts. The latter then 

 strike alternately with a rapid, plunging movement, while 

 the poison is pumped down from a chamber at the base 

 of the shaft. Two glands, one acid and one alkaline, 

 minister to this deadly flow ; for while the combined liquid 

 is always acid, an alkaline admixture appears to be neces- 

 sary to render the poison lethal. It is said that in insects, 

 such as digger-wasps, which merely paralyse their prey, 

 the alkaline glands are functionless or abortive. More- 

 over, in these insects, and in most other stinging Hymen- 

 optera, the darts of the sting are far less formidably barbed 

 than is the case with the worker hive-bee. Thus, the 

 sting can be readily withdrawn ; whereas the bee com- 

 monly leaves her weapon sticking in the wound, and 

 suffers a fatal rupture — a remarkable sacrifice of the 

 individual for the benefit of the species. Mr. Cowan tells 

 us, however, that if time is allowed the bee can withdraw 

 her sting by a spiral motion, similar to drawing a cork- 

 screw out of a cork ; but she is usually far too agitated 

 to go through this slow performance. The sting of the 

 queen hive-bee is curved, and only slightly barbed, while 

 the contents of her poison-sac differ materially from that 

 of the worker's. We shall see later that this royal weapon 

 is used to despatch rivals when the state of the community 

 does not warrant the sending forth of a swarm. 



Many ants are armed with a sting, but in other species, 

 such as the common wood ant {Formica rufa)> the poison- 



