WASPS 203 



support, and direct the delicate needles within, and is therefore 

 known as the " director/' When a sting is inflicted a hole is 

 first made by the " director/' the needles are then slid along 

 inside their sheath, so that they issue side by side from the hole 

 at its extremity and penetrate more deeply into the flesh of the 

 enemy. The opposed faces of the needles are channelled each 

 by a deep half-pipe gutter, so that the two together enclose a 

 tube between them ; into the anterior end of this pipe poison 

 is discharged by a tube leading backwards from a bag, the poison 

 bag, in which this liquid is formed ; the poison is forced along 

 between the needles and escapes into the inflicted wound through 

 minute canals perforating the base of the barbs, which serve 

 for the time to anchor the needles in the flesh. In the cavity 

 of the " director " are rows of projecting studs, which guide the 

 outer edge of each needle and prevent any dislocation of the 

 parts. 



Breathing. A living wasp, even when quite undisturbed, 

 maintains a constant in-and-out telescopic kind of motion of the 

 abdominal segments, as though threatening to sting. These 

 movements are in reality concerned with respiration. Insects 

 do not breathe through the mouth, but through a number of 

 holes (stigmata or spiracles) on the side of the body. In the 

 wasp there are six of these breathing holes on each side of the 

 abdomen, and three on each side of the thorax. The abdominal 

 stigmata can just be seen with the unaided eye if the specimen 

 be well stretched out ; one is situated on each side in the black 

 part of the dorsal semicircle of each segment near its ventral 

 edge where it overlaps the ventral semicircle, and is itself over- 

 lapped by the dorsal part of the preceding segment. The thorax 

 also possesses three pairs of stigmata, one belonging to the pro- 

 thorax, the second to the mesothorax, and the third to the pro- 

 podeum ; these, however, are by no means easy to see, owing 

 to the overlapping of the hard parts of the thorax. The stig- 

 mata lead into tubes, called tracheal tubes, which are connected 

 on each side by longitudinal air-vessels and penetrate into all 

 the tissues of the body, conveying air direct to all parts by means 

 of the numerous ramifications into which they subdivide. These 

 tracheal tubes are really delicate, inward extensions of the external 



