J\Ir. Foggo oil an Ins tcl J omul in the wood of a Table. 289 



been considered quite analogous to the well-known facts of 

 reptiles being found alive in solid locks, and have been re- 

 ferred to the same cause, a temporary suspension of the vital 

 functions. The circumstances, however, are essentially 

 different. We have reason to believe, that the reptiles were 

 enclosed in the same state as wher» they were discovered. 

 But with respect to the insects, in whatever state they enter- 

 ed the tree, they must have undergone some of the different 

 processes of transformation. It becomes, therefore, interest- 

 ing to ascertain in what state the animal has existed during 

 its confinement, and what are the causes which have retard- 

 ed its advancement to maturity. A late author had conjec- 

 tured, that the ovum from which the insect was produced, 

 having been prevented from undergoing the necessary evolu- 

 tion, had retained its animating principles till summoned into 

 action by some change in its relation to external objects ; 

 and further, that it might have lain dormant for an indefinite 

 space of time. The same author has likewise endeavoured 

 to explain in this manner the periodical visitation of the lo- 

 cust, palmer worm, Hessian fly, &c. with the additional hy- 

 pothesis that certain modifications of the atmosphere may be 

 peculiarly favourable for their production. This explanation, 

 iiowever, is liable to several objections. It is difficult to 

 conceive any cause that could operate year after year in 

 preventing the animal from arriving at maturity, and that too, 

 apparently' in the very situation selected by the instinct of 

 tlie mother. Moreover, on examining the cavity in which 

 this animal was lodged, it is evident that, while within the 

 tree, it must have passed its life in an inert state. This is a 

 fact which is scarcely consistent with our knowledge of the 

 economy of insects, for they are, I believe, always most vo- 

 racious in the larva state. It is, therefore, most probable^^ 

 that the larva penetrated the tree in order to prepare for 

 becoming a chrysalis, and having at last assumed its perfect 

 Ibrm, emerged into light in the usual time. That the insect 

 made its appearance in the ordinary period peculiar to the 

 species, is rendered probable from several collateral facts. 

 It is well known that several species of insects remain in the 

 chrysalis for many years ; that the locust appears in numbersj 

 once only in 17 yi ars, and the palmer worm in 30 years, yet 

 these are cycles not recognised by meteorologists. The tribe 

 Urocerata is also subject to periodical swarming, " et pa- 

 laissent certaines annees en telle abondance quils ont ete po'ur 

 Vol. IX.— No. 2. 37 



