400 ENTOMOLOGICAL NEWS [Nov., '12 



Their movements were a combination of squirms and wriggles 

 amounting almost to convulsion ; the fore body was frequently 

 thrown violently from side to side and the caterpillar would 

 often make attempts to remove any eggs placed upon either 

 side by biting or by rubbing or shaking them off. They emit 

 fluid from the mouth. No matter how they would contort 

 themselves, however, they could not reach the region of the 

 cervical shield where the flies were obviously attempting to de- 

 posit their eggs. By observation, it was demonstrated that 

 this region was the safest place to lay them. Generally several 

 flies would attack the same larva. Their eggs were often mis- 

 placed, occurring on any portion of the dorsal aspect of the 

 body. In one of these cases a caterpillar, upon which there 

 had been two eggs misplaced, removed one by rubbing the head 

 against it. However, misplaced eggs were not always re- 

 moved within the time limits of the observation. They are 

 easily removed from a caterpillar's body with the hand and 

 are rather easily crushed. 



Thus, we have here an undoubted explanation of the resting 

 attitude noted above ; the cervical shield is protected by bend- 

 ing back the fore body, while the upcurved hind body aids the 

 protection by preventing access from behind. That the pro- 

 tection is not perfect is to be expected, but it is acted upon by 

 natural selection and only those larvae practicing it obtain the 

 greatest freedom from death following parasitism from those 

 eggs which will be the most successful, namely those placed 

 behind the head. In regard to the origin of the habit in the 

 flies themselves, natural selection has again acted, since only 

 those eggs safely placed would survive. Through the accu- 

 mulated inheritance of acquired characters, the placing of the 

 eggs in safety would become a habit which by the further 

 action of heredity would become instinctive. As regards the 

 obvious fear expressed in the movements of the caterpillars 

 when being pursued by parasites, it must be considered as be- 

 ing- of the same nature as fear in other animals, including 



o 



man. Here it certainly seems to be conscious, though expected 

 to be unconscious; a horse indicates consciousness by turning 



