'2C)0 [April, 



Longevity in a beetle. — On the 15th April, 1878, M. Rene Oberthur sent to me 

 from Eenncs a living pair of the well-known Dytiscus Raeselii, Fab. ; the insects came 

 bj post in a small tin box with some wet moss, and arrived apparently in perfect 

 health ; they had a fresh appearance, and as the larger Dytiscidce are, I believe, all 

 transformed to perfect insects at the end of summer or in the autumn, they had 

 probably, at that time, been perfect insects for about six or eight months ; they may 

 have been older than that, but I do not consider it probable they were. The insects, 

 on their arrival, were placed in a vase of fresh water, and were fed at intervals on 

 pieces of earth worm or tadpoles, and seemed to be quite healtliy under this regime. 

 The male died about two years since in the spring, but the female has continued 

 vigorous until recently ; at the commencement of the present month she was noticed 

 to be weak and disinclined for food, and though she took small quantities of nourishment 

 two or three times after this, she did not recover her activity, and on the 9th instant 

 was found dead. Thus this specimen had lived nearly five years with me in this 

 vase of water, and had pretty certainly been a perfect insect for a period of about five 

 and half-years, if not longer. The earlier stages in the metamorphosis of the Dytiscidm 

 are, I believe, all passed through with rapidity, so that the total duration of life of 

 the individual under discussion would be about five and three-quarter years, or less, 

 at any rate, than six years. Sir John Lubbock has, I believe, recorded as great, or 

 even greater, a longevity in the case of some ants, but such a long life has, so far as 

 I am aware, not been previously observed in any beetle. Lacordaire, in his Intro- 

 duction a I'Entomologie (Vol. I, p. 214) when discussing the duration of life of 

 insects, alludes to the fact that Roesel kept an individual of Cetonia aurata alive for 

 nearly three years, and Esper a specimen of Dytiscus marginalis for about three 

 and a half years. 



Two days after the decease of this specimen, I made a slight examination of its 

 internal organs, in order to ascertain the condition of the ovaries. On opening the 

 hind-body the most remarkable object was the bursa copulatrix, or spermatic vesicle, 

 which was of enormous size, distended and occupying about one-fourth of the area of 

 the hind-body or abdomen. The ovaries were small, and their tubes contained no 

 eggs, but were full of an albuminous substance with darker spots in it, the material 

 I imagined of undeveloped ova. The bursa copulatrix, on being opened, was found 

 to be full of a clear fluid, which, after a moment or two, became very slightly milky, 

 and gave forth an extremely powerful foetid odour, similar to that which collectors 

 who have captured the larger Dytiscidce must frequently have noticed, as being the 

 result of a discharge of liquid from the extremity of the body. The condition of the 

 ovaries surprised me ; as I have no reason for supposing that eggs have ever been 

 deposited by this individual, I had expected to find the ovaries much more largely 

 developed. According, to my experience, it is extremely difficult to obtain oviposition 

 from the larger Dytiscidce in confinement ; Dr. Eeginibart has, however, been more 

 successful, and it would appear from his observations (Ann. Soc. Fr., 1875, p. 201) 

 that special conditions arc necessary to induce the female to lay her eggs ; it would, 

 indeed, seem, if we may judge from the condition of my specimen of D. Roeselii, that 

 even up to tlie period of the extreme limit of life, and long after fertilisation (for 

 such occurred in the present case) the eggs do not become developed in the ovaries 

 unless the individual be placed in cireimistances suitable for their deposition. Such 

 an ini})ortunt physiological induction as this requires, however, more complete 



