46 



Granting that many habits may arise from external causes, let us 

 be careful how we speak of them in relation to the insect producing 

 them. We are often in the habit of speaking of such and such an 

 organ as being wonderfully adapted to the habits of the insect possessing 

 it ; but do not these considerations rather suggest that it would be 

 more correct to say that the habit was wonderfully adapted to the organ ? 

 Instead of saying that a certain organ enables an insect to perform a 

 certain action, would it not be more accurate to use such words as 

 compels, constrains, or urges? Let me give a few examples to make my 

 meaning clear. The bifurcators of C. pnsio compel it to remain within 

 its case ; the anal feet force it to grasp the wall of its dwelling, and 

 the pain-hairs compel it to shrink when touched: the stiffening spines 

 urge the pupa forward until the operculum is burst off the pupal-case : 

 the particular articulation of the limbs of the Cockroach and other 

 Blattidae constrain them to live in cracks and crevices : the palmate 

 hairs on the abdomen compel Anopheles to maintain a fixed position 

 during respiration. The function of the palmate hairs has only lately 

 been pointed out by NUTTALL AND SHIPLEY, who write " The whole 

 [bundle of hairs] forms a most delicate little cup, and it is by means 

 of these five pairs of palmate hairs, which cling to the surface film, 

 that the larva maintains its position close under the surface of the 

 water." 



To speak of optic, auditory or olfactory stimuli compelling an insect 

 to act in a certain way is no new thing. We are accustomed to speak 

 of a bright light drawing, attracting or fascinating a moth, or an odour 

 alluring one sex to the other; so that to claim that cutaneous sensations 

 should govern an insect's actions is really only an extension of a well- 

 known principle. This principle, with its enlarged meaning, is that the 

 insect is driven to its actions by direct sensations arising from the 

 stimulus of all sensory nerve terminations whether they belong to the 

 special or the general senses, or by tendencies that ar*e themselves the 

 product of direct sensations. 



It will be advisable to state shortly the three ways in which we 

 can account for insect actions. First we have those actions which are 

 the result of innate tendencies, born in the animal, and resulting from 



