48 Trans. Acad. Set. of St. Louis 



no doubt, would agree with Holmes that " it is among the 

 insects that the death-feigning instinct reaches its highest 

 development, occurring, in a greater or less extent, in 

 most of the orders. It is especially common in beetles 

 and not unusual among bugs, but it is quite rare in the 

 highest orders such as the Diptera, or flies, and the 

 Hymenoptera, or ants, bees and their allies. It occurs in 

 a few cases among the butterflies and moths, both in the 

 imago as well as the larval state. The instinct is ex- 

 hibited in different species in all stages of development 

 from a momentary feint to the condition of intense rigor 

 lasting for over an hour. ' ' Some insects may be severely 

 mutilated, ' ' according to De Geer, ' ' even roasted over a 



fire before they cease feigning. ' ' 



At the planning of this paper it was intended to give 

 an epitome of the researches of all recent investigators 

 of letisimulating insects ; but later it was decided to limit 

 this part of the paper to recent investigations of mine 

 upon our common ant-lion. Although the ant-lion is con- 

 sidered such a marvel that all popular treatments of 

 insects and practically all textbooks on entomology dis- 

 cuss it, hitherto almost no attention has been paid to its 

 death feigning. Emerton (Amer. Nat., 1871, Vol. IV, pp. 

 705-708) and MacLachlan (Ent. Mag., 1865, Vol. II, pp. 

 73-75) are the only ones that mention it and each devotes 

 only a short sentence to the matter. 



One hundred ant-lions, isolated in numbered jelly 

 glasses of suitable soil formed the subjects of these inves- 

 tigations. These were kept in an out-of-doors insectary, 

 the whole north wall of which is exposed to the weather. 

 Although any kind of rough treatment will cause an ant- 

 lion to letisimulate, in these experiments letisimulation 

 was induced cither by roughly turning the creature upon 

 its back, or else by dropping it from a slight elevation. 



