ACTIVE DEFENCE 



359 



ejected with a slight noise, giving at the same time the appear- 

 ance of a minute puff of smoke. One of the little Click- Beetles 

 (Lacon murinus), of which the larva attacks corn-crop, is provided 

 with a pair of stink-glands, which open near the tip of the abdomen 

 and secrete an extremely-offensive fluid. The protection afforded 

 would appear to be considerable, for it is stated on good authority 

 that when attacked this beetle makes no attempt to escape, but is 

 content with assailing the nose of the enemy with evil smells. In 

 the Mole-Cricket {Gryllotalpa campestris) there are stink-glands 

 in much the same position as in the Bombardier- Beetle, and glands 

 of similar kind open on the upper side of the abdomen in Earwigs. 

 The order of Bugs (Hemiptera) has been much neglected, even by 

 specialists, and this is no doubt partly due to the fact that very many 

 of them, especially the plant-feeding forms, are provided with stink- 

 glands, of which the secretion is decidedly offensive. It is a 

 curious fact that in many such species the young are provided 

 with glands of the kind which open on the upper side of the 

 abdomen, but these are replaced in the adult by similarly-endowed 

 structures opening on the sides of the thorax. The larval glands 

 would not be of much use if retained, for their openings would be 

 covered over by the wings. 



The Stick- Insects (Phasmidce) are provided with defensive 

 glands in the thorax, of which the secretion is reputed to be 

 extremely acrid as well as malodorous. It can be ejected with 

 considerable force, and it is stated that blindness may result 

 should it happen to get into the eye (compare p. 303). The 

 caterpillar of the Puss Moth (Cerura vinula] is one of the forms 

 which assume a terrifying attitude (see p. 313), and to this mode 

 of defence is added the one now under consideration. Lodged in 

 the front part of the body there is a gland secreting an irritant 

 fluid containing as much as 40 per cent of formic acid, and this 

 can be squirted out upon an attacking enemy, proving most 

 effective when it happens to hit the eye. Poulton (in The 

 Coloiirs of Animals] speaks as follows of this secretion and its 

 properties: " So far as we know at present, no other animal 

 secretes a fluid containing anything which approaches this per- 

 centage [40] of strong acid. . . . The value of this strongly- 

 irritant liquid is sufficiently obvious. I have seen a marmoset 

 and a lizard affected by it, and have myself twice experienced 

 sharp pain as the result of receiving a very small quantity in the 



