10 



In the species belonging to Platypus and Xyleborus the female de- 

 posits her eggs loosely in the galleries or brood chambers, and young 

 and old live together socially in the same quarters. 

 . The species belonging to the genera Corthylus, Monarthrum, Xylo- 

 terus, and Gnathotrichus rear their young in separate pits, which the 

 larvae never leave until they transform to perfect insects. 



The nature of the food of the timber-boring Scolytidre has always 

 been a matter of considerable uncertainty and mystery. Schmidberger 

 first, in 1836, treating of Xyleborus dispar, declared that the food con- 

 sists of a substance coming from the wood and elaborated by the 

 mother beetle to form " a kind of ambrosia." Subsequently Eatzeburg, 

 Altum, Eichhoff, and others confirmed the observations of Schmidberger, 

 but added only vague speculations as to the nature of his " ambrosia." 



In 1844 Theo. Hartig x^ublished an article on tbe ambrosia of Xyle- 

 borus (Bostrichus) dispar, in which he showed that it was a fungous 

 growth (pilzrasen) and he named the fungus Monilia Candida. 1 



The subsequent speculations of various authors have added nothing 

 to our knowledge. In fact, until quite recently, Hartig appears to have 

 been the only writer who has taken the trouble to make a microscopic 

 examination of the so-called ambrosia. In a later writing (1872) upon 

 two species of Xyloterus, the one living in fir and the other in beech 

 wood, the same author states that two distinct kinds of fungus are con- 

 nected with these two sorts of wood. In 1895 R. Gothe 2 published an 

 excellent figure of the ambrosia of Xyleborus dispar. 



The correctness of Theo. Hartig's and Gothe's observations may be 

 easily verified. A small fragment of ambrosia taken from the gallery 

 of any species of these timber beetles, if placed on a glass slide, with a 

 drop of water or glycerine and examined with an objective of moder- 

 ate power, is plainly seen to be a fungus. It will be found, however, 

 that the different kinds of ambrosia fungi are connected with certain 

 species of the beetles irrespective of the sort of timber in which the 

 galleries are constructed. So far as we yet know the food of each spe- 

 cies of ambrosia beetles is limited to a certain kind of ambrosia, and 

 only the most closely related species have the same food fungus. 



Two principal types exist among the varied forms of these minute 

 fungi : (1) Those with erect stems, having at the terminations of the stems 

 or their branches swollen cells (conidia; figs. 4, 20, 23). (2) Those 

 which form tangled chains of cells, resembling the piled-up beads of a 

 broken necklace (figs. 6, 26, 32). The erect or stylate forms are found 

 among those species of the beetles whose larvae live free in the galleries 

 (Platypus and Xyleborus). The bead-like or moniliform kinds appear 

 to be peculiar to the species whose larvae are reared in separate cells 

 or cradles (Corthylus, Monarthrum, etc.). 



^llgemeine Forst -und Jagdzeitung, B. 13, p. 73. 



2 Bericht d. kgl. Lehranstalt fiir Obst-, Wein -und Gartenbau zu Geisenheim, 

 1894-95 (1895), p. 25. See also Dr. E. F. Smith in Amer. Nat., vol. 30, 1896, p. 319. 



