596 EDWARD M. NELSON ON VARIOUS INSECT STRUCTURES. 



useful, but also a fascinating branch of microscopical study. 

 We will now pass on for a moment to the Vespa crabro, or 

 hornet. If its sting be examined with a 2/3rd inch objective 

 the barbs, A, fig. 2, will be seen ; B is a tube, and C a razor blade. 

 Fig. 3 shows the sting in section. The fine tubules, three below 

 the last barb and one below each of the others, will be seen. The 

 breadth of the sting in fig. 2 is 110 fx, the width of the razor blade 

 33 fx, the length of a barb 17 /x, the length of a tubule 25 //,, and its 

 width 4*2 fx. If the sting happens to be well placed the exit 

 pore of a tubule may be caught. It is probable that these stings 

 are homologous with the saws in the ovipositors of insects. 

 Instead of barbs there are bold saw-like teeth, which, unlike 

 those in a carpenter's saw, go round the side of the saw the 

 holes for the emission of lubricating or poisonous fluids are 

 numerous and much easier noted than those on the sting of a 

 hornet. The ovipositor of a dragon-fly is a good example. 



In conclusion, I would draw your attention to the pygidium 

 of a flea. If the right- and left-hand edges be examined a hole will 

 be found ; this is an Eustachian tube. The apparatus corresponds 

 to the drum of an ear, and must like it have an air passage to 

 equalise the pressure on either side. Now look at the base of 

 the haltere in a blow-fly, where a similar tube will be easily seen. 



Joum. Quekett Microscopical Club, Ser. 2, Vol. XII., Nc. 77, November 1913. 



