OAK-BORERS. 63 



The burrows of the Buprestid larvae may nearly always be distin- 

 guished, says Ferris, by their tortuous course, and by the fact that the 

 excrement and detritus, instead of being accumulated iu the gallery 

 without order, are there disposed in small layers forming concentric arcs, 

 whose opening is turned away from the larvae, and of a regularity not 

 less remarkable than characteristic. 



This symmetrical arrangement has as its primary cause the dimensions of the gal- 

 lery, which are out of proportion with the abdomen of the larva. The latter, because 

 of the size of the anterior portion of its body, is obliged to give to its gallery a size 

 sufficient for the posterior part to execute freely movements of advance and retreat, 

 which have as their natural result the disposition en arc of the rejected material be- 

 hind. On the other hand, the larva, in consequence of the dimension y of its gallery, 

 in order to have points of support is obliged to bend the posterior part of the body 

 on itself. It is, indeed, ordinarily found in this attitude, which allows it to press 

 against the walls, so as to push itself ahead ; but in this condition the abdomen forms 

 an arc which, propping itself from the convex side on the detritus, causes the concav- 

 ity of the successive beds. * * * 



We have seen that some Buprestid larvae undergo their metamorphoses in the inte- 

 rior of the bark, others in the thickness of the wood. It is, moreover, in this that the 

 wisdom of nature is revealed, for it is not capriciously and without motive that things 

 happen as I have described. We know, indeed, that if those larv;© which do not at- 

 tack the young trees, as those of Ancylocheira 8-gutiata, of Chysobothris solieri, and of 

 Anthaxia morio, and of several species of Agrilus, should live under the bark they 

 would not be sufficiently protected, because the bark is not thick enough and would 

 easily separate from the wood. When, however, on the contrary, they live under the 

 hard and thick bark of old trees, as Melauophila tarda, Chrysobothris affinis, Agrilus 

 biguttatus, and A-guttatus, and others, they do not hesitate to take refuge in the bark, 

 because they are there well sheltered, and because they save the beetle from making 

 a long and difficult journey in order to make its exit. * * * 



What is the duration of the life of the larvsB of the Biqyrestidwl Ratzeburg is 

 inclined to believe that it is two years. M. Levaillaut, whose observations are repro- 

 duced by M. Lucas in his notice of Chalcophora, is also disposed to think that those 

 of this insect pass two years in the wood. The reason which he gives, and which is 

 drawn from the size of the larvse found from December to August, does not seem to 

 me conclusive, because the female of Chalcophora is capable of laying eggs daring 

 almost the entire year. As to M. Ratzeburg, he has not, apparently, made careful 

 observations in this respect. 



As to myself, numerous facts authorize me to say that, in general, these larvae only 

 live one year. For example, some pines, poplars, and willows which I have cut down 

 in the springtime, with the design of obtaining Buprestids, have afforded me often 

 very numerous perfect insects iu May and June of the year folio wiug. 



Some logs of oak, cut in January, 1847, and which lay during a whole year in the 

 open air, furnished me in June and July, 1848, more than three hundred Chrysobothris 

 affiim. The trunks of some large, very rigorous pines, cut down at the beginning of 

 one year, contained pupie of Ancylocheira in the following May. Finally, as regards 

 all the species that I have here described, and for a number of others, I have, from 

 my own experience, the certainty that the larvae live only oue year. 



I admit that, without doubt, among these larvae there are some which, not placed in 

 conditions sufficiently favorable to complete during this period all the phases of their 

 existence, from one cause or another, may be retarded some months, for a year even. 

 I moreover accept the more willingly this fact, because I have had good occasions for 

 observing this in larvae which I have raised in my cabinet ; but this is the exception, 

 and the rule is that a single year suffices, in our country, for the development of the 

 larvteof the Buprestidae. 



