SOME NEW BOOKS. 



BARK-BEETLES 



De Danske Barkbiller (Scolytidae et Platypodidae Danicae). By E. A. 

 L0VENDAL. 4to, pp. xii. + 212 with figs, and 5 pis. Copenhagen, 1898. 



From the earliest period of modern natural history research the Bark-beetles 

 have attracted much attention. Their importance as widespread destroyers of 

 trees (rarely of other plants, as in the case of Xyleborus morigerus, an exotic 

 species now only too common among Dendrobiums in European hot-houses), 

 and the singularity of their burrows in bark or wood have given rise to a 

 literature, beginning with the last century tracts on the " Wurmtrockniss " or 

 destruction inflicted on conifers by various species of Ips (Tgmicus), which is of 

 surprising extent, and with which, concealed as much of it is in obscure period- 

 icals on Forestry, etc., it is difficult to obtain a competent acquaintance. For 

 all but historical purposes, however, it may be said to begin with Batzeburg's 

 " Forst-Insekten," a work which laid the foundation for the scientific study of 

 forest entomology. 



With entomologists not concerned with economic work the study of this- 

 family has not proved popular, and it is only in the last thirty years or so that 

 anything has been known about extra-European species. This is not surprising, 

 for the insects are small and obscure, and often so alike in appearance, that 

 they cannot be satisfactorily determined except after prolonged study, not only 

 of the simpler external features, but of the mouth-parts, antennae, and legs, a 

 task requiring much tedious and exacting microscopical work. 



They are nevertheless well deserving of study by every one who is prepared! 

 not to measure the importance of systematic work by the showiness of the 

 collections on which he is engaged. Accurate determination is the first necessity 

 in the case of many economic problems presented by these beetles ; indeed,, 

 without it divers of them are incapable of solution. And even if the European 

 species present no great variety of structure, the exotic forms sometimes exhibit 

 a singularity that is scarcely exceeded by any family of Coleoptera. 



The habits of the ordinary bark-burrowing Scolytids are peculiar among 

 beetles ; still more strange are those of the wood-borers, who, though they tunnel, 

 do not feed on wood but on fungus growths, which, as Habbard has lately 

 shown, are artificially propagated by the insects themselves. 



In Xyleborus, one of the best known of the wood-boring and " ambrosia- 

 feeding " genera, the males are sub-apterous, dwarfed, and often of bizarre form 

 (in X. morigerus the male is relatively so minute that it might be mistaken 

 for an insect of a different genus or even family from the female). Moreover, 

 they are very much the rarer sex, their numbers varying from one in four to 

 one in fifty, or thereabouts ; the species are therefore polygamous, and must 

 in most cases inbreed, a fact which does not prevent the genus from being one 

 of the richest and most widely-distributed of the Scolytidae. 



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