CHAP. IV.J 



MEANS OF DEFENCE IN INSECTS. 



53 



Chapter IV. 

 MEANS OF DEFENCE IX INSECTS. 



t animal est tres mechant, 

 Quand on 1' attaque il se defend.'' 



THE means of defence adopted by insects against the attacks 

 of their tin-mil- are very numerous and can only be touched on 

 here very lightly but, broadly speaking, they may be divided into 

 (i) passive and (2) active defence. In the first group we find pro- 

 tective resemblance and mimicry, etc., whilst warning coloration is 

 perhaps intermediate between the two groups, active means of 

 defence including the use of more or less poisonous bites or stings, 

 urticating hairs, the discharge of [acrid, volatile or nauseous 

 liquids, etc. 



~ 



Fig. 18. — Sathrophyllia rugosa, a long-horned grasshopper common on tree 

 trunks in Southern India. (Original.) 



Protective resemblance is probably the most primitive and also 

 in modern times the most usual (and hence, we may add, the most 

 successful) method of defence practised by insects, and under this 

 term are included all cases in which insects resemble their surround- 

 ings or any object commonly found in those situations in which 

 they occur normally. Millions of years ago, when the Coal 

 Measures were being deposited in the Palaeozoic Epoch, the cock- 

 roaches of those ancient times had acquired a type of neuration 

 strikingly similar to that found on the fronds of a fern (Neuropteris 

 odontopteroides) which was one of the plants from which the coal 

 was derived. In modern days the prevalence of protective resem- 

 blance is best (and perhaps only) appreciated by the eye trained 

 by field observation. On pointing out some protectively-coloured 

 animal in its natural surroundings, nothing is commoner than the 

 observation, "However can you see such things? I never see them ;" 

 3-a 



