190 PROTECTION AGAINST INSECTS. 



like material, and are constructed on trees, in a hollow trunk 

 or suspended from a branch, or in buildings or a hole in the 

 ground. Just before pupating, the larvae spin covers to their 

 cells. The J? become torpid in the autumn, and their last 

 office is to massacre the undeveloped brood, which would 

 otherwise die of hunger, as their food-providers themselves 

 are speedily killed by the increasing cold. The fertile females 

 alone leave the nest and survive the winter in a dormant 

 condition, reviving in the spring to provide fresh broods for 

 the future. 



Wasps seize insects, especially moths and flies, partly for 

 their own nourishment and partly to use their juices as food 

 for their offspring, or even to feed them with 

 the living insects. They do a certain amount 

 of damage by eating sweet fruits, plums, 

 grapes, etc., and especially the hornet (Vespa 

 crabro, L.), by girdling 2 to 4-year-old shoots of 

 beech, birch, hornbeam, etc., and by barking 

 ash, white alder, etc. ; they prepare the bark by 

 chewing and mixing with a sticky secretion, and 

 7_~~"~ use it for the fabrication of their nests. Bark- 

 Wasp-bottle. ^ n g f ^ rees a l so causes a flow of sap which serves 



as food. 



Where much damage is done, hornets' and wasps' nests 

 may be smoked out, or tar, kerosene, or a solution of cyanide 

 of potassium poured into the entrance holes. Glasses con- 

 taining beer, etc., for catching them, as shown in Fig. 72, may 

 be hung up on fruit trees. 



4. Formicidae (Ants}. 



Ants also have three classes males, females, and workers. 

 The head is triangular and very large in the J? . There are 

 three ocelh, at least in the $ and ? . The antennae have 10 14 

 joints. The wings are long and with few veins. The 

 abdomen is stalked and often spherical, with a sting at its 

 extremity, or a gland which exudes formic acid. The $ are 

 generally much smaller than the ? ; both these sexes have a 

 well-developed globular thorax, wider than the head, and a 

 large abdomen. In the J? the thorax is very narrow, much 



