398 THE NATURAL HISTORY 



onward course of the latter species, the more par- 

 ticularly as it had occurred to me that those butterflies 

 whose wings were of a lax texture with slender 

 nervures, displayed this particular means of avoiding 

 their pursuers, of which those possessing stronger 

 nervures with an apparently more tense membrane 

 between them, would seem to have no need. While I 

 was indulging my speculations upon this conjecture, 

 two individuals of Vanessa Urtica that had repeatedly 

 flown by me, now alighted on a broad blade of grass 

 not a yard off, and I had ample opportunity of watch- 

 ing them for some time. One had fixed itself in an 

 attitude, which though singular and perhaps not very* 

 graceful, is by no means unusual with this beautiful 

 order of insects ; I mean with its abdomen raised so 

 as to form an angle with the thorax, its antennae and 

 wings extended and motionless. The other, about 

 half-an-inch behind it, was displaying a most fantas- 

 tical behaviour, and with as much agility as the 

 narrow space on which it was moving would allow, 

 traversing it from side to side, then closely approach- 

 ing the inactive one and receding from it by sudden 

 starts, and what more particularly arrested my atten- 

 tion, frequently striking its antennae against each 

 other so forcibly as to produce a click or snap 

 distinctly audible to me as I stood upright, and I am 

 no pigmy. 



"At that time I had never heard the noise pro- 

 duced by the larva of Acherontia Atropos (Death's 

 head Sphinx) ; but since then I have though out of 

 nine individuals that I had the good fortune to obtain 

 last year, one only produced the noise in question 

 and I am enabled to assert that the click produced by 

 the butterfly ( Vanessa Urticce) was by far the strongest. 

 I remained watching three or four minutes, during all 

 which time the scene I am describing continued with- 

 out any interruption, the clicking being frequent and 

 perfectly audible. On a slight motion I unintentionally 



