176 THE ENTOMOLOGIST. 



E. cribrum, but few will have realized more pleasure, or had 

 greater facilities for its capture, than I have had in the past. 



Eingwood : June 7th, 1899. 



PHYSIOLOGICAL EXPEEIMENTS UPON DYTICUS 

 MARGINALIS, Linn. 



By Henki Gadeau de Kerville.* 



Dyticus marginalis lends itself very well to physiological ex- 

 periments, as it is very hardy and endures captivity excellently. 

 For nourishment, small pieces of meat of some kind are sufficient. 

 Its gluttony is such that not only does it devour those of its 

 kind who have expired, but even attacks — at least in captivity — 

 those in whom a little life yet remains. I have observed that it 

 gnaws the posterior extremity of the elytra first of all, then the 

 integument of the postero-inferior part of the abdomen, to eat 

 the contents. 



I have remarked, as has also our learned colleague Dr. 

 Maurice Regimbart,t that a male of D. marginalis can fecundate 

 two or three females in a relatively fairly short time ; in one of 

 my experiments a male fecundated three females in less than 

 three weeks. 



Desirous of ascertaining whether the males, possessed by an 

 imperious sexual desire, would copulate with a dead female of 

 their species — a fact observed in other insects — I left dead 

 females with very vigorous males (a couple in each bowl) for 

 some weeks without observing, on the part of the last, any 

 amorous propensity ; these males manifested upon them their 

 voracity, however, to a slight degree. I killed the females a 

 short time before the experiments by means of alcohol or chloro- 

 form, and left them for half an hour beneath a stream of running 

 water to rid them of any odour from the destroying liquid. I 

 also kept males only for some time in small basins, to see if they 

 would attempt copulation ; I have not observed even an attempt 

 at paederasty. 



It is, however, the action produced upon Dyticus by cold, 

 heat, deprivation of atmospheric air, by chloride of sodium and 

 of magnesium, that I have particularly studied. A number of 

 more or less analogous experiments have already been made by 

 eminent physiologists, among them Paul Bert, Leon Fredericq, 



* 1897, Bull. Soc. Ent. France, pp. 91-7 (translated by G. W. Kirkaldy). 



These experiments were made upon fifty male and female individuals of 

 Dyticus marginalis, L., which were obtained for me by my friend Mr. Paul 

 Noel, the zealous director of the " Laboratoire regional d'Entomologie agri- 

 cole " of Rouen. 



f Ann. Soc. Ent, France, 1877, p. 268. 



