222 • THE CANADIAN ENTOMOLOGIST 



an interpretation the death feint among insects falls into one or 

 other of the three divisions which follow: 



1. The insect on receiving a shock becomes rigid without re- 

 leasing its hold. 



Certain caterpillars will hold on to a twig by one or more 

 pairs of prolegs, and elevate their bodies, assuming more or less 

 grotesque rigid attitudes in which they will remain for a con- 

 siderable time. Perhaps the best known examples are the cater- 

 pillars of the Sphinx Moths and of certain geometers. In these 

 cases the insect seems to come to rest naturally in the immobile 

 attitude, without the stimulus of a shock, the contraction of the 

 muscles being probably due to an internal stimulus resulting from 

 the active metabolism which takes place after the insect has eaten. 

 If such is the case these reactions cannot properly be described 

 as death feints. In other insects, however, a similar attitude 

 can be definitely brought about by a shock. Thus if the yellow- 

 necked apple-tree caterpillar {Datana ministra) be disturbed it 

 will raise both ends of its body with a jerk, retaining hold of the 

 twig by means of the four pairs of anterior prolegs. 



?. The insect when disturbed rolls itself into a motionless ball. 



This habit seems to be common among terrestrial forms rather 

 than among arboreal ones. The ruby wasps or cuckoo-flies (Chry- 

 sididae) lay their eggs in the nests of wasps and bees. If attacked 

 by their hosts the ruby wasps bend their abdomen beneath the 

 thorax, and in this attitude resemble a small, metallic ball. 



Sometimes the head and abdomen are bent back above the 

 thorax. Thus Kirby and Spencer say of Silpha thoracica "when 

 alarmed it turns its head and tail inwards until they are parallel 

 with the trunk and abdomen and give its thorax a vertical direc- 

 tion, when it resembles a rough stone." 



Certain of the rove beetles (Staphylinidse) combine both at- 

 titudes, bending the head beneath the thorax and the abdomen 

 above the elytra. 



Many cutworms and other caterpillars also roll themselves 

 into a motionless ball when disturbed. 



S. The insect releases its hold, contracts its legs and antennce 

 and falls to the ground, where it usually remains motionless and ap- 

 parently dead. 



