394 ^^^^' VORK STATE MUSEUM 



A^rUKOSIA BEETLES 



This small group of insects is remarkable because the different species 

 live on various succulent fungi carefully grown in their galleries. These 

 interesting forms have been closely studied by the late H. G. Hubbard of 

 the Division of Entomology, United States Department of Agriculture, and 

 the following account is based on his published observations. These little 

 wood borers are easily recognized by their somewhat elongate, cylindric 

 form and specially by their habit of making uniform sized galleries in the 

 wood of various trees. The burrows usually penetrate to a considerable 

 depth, have a well marked design, and their walls are stained a bluish 

 or black color by the fungus. The exits of the galleries are circular and 

 from them are ejected minute white chips, which may frequently be 

 observed on the rough bark or the ground beneath. These little beetles 

 are remarkable for the care bestowed on their young, and in this exhibit 

 characteristics foreign to most Coleoptera, and such as we expect to find 

 only among the social bees, ants and their allies, and Neuroptera, such 

 as the well known white ants. 



These borers require special conditions for the propagation of their 

 food fungus, and consequently can inhabit only certain trees. This fungus 

 does not appear by accident but is carefully propagated by the mother 

 beetle on a packed bed or layer of chips, sometimes near the entrance in the 

 bark though usually at the end of a branch gallery. The ambrosia of some 

 species is grown only in certain brood chambers of a peculiar structure, and 

 in others in beds near what Mr Hubbard considers larval cradles. The 

 excrement of the young is used in some and probably in all species, to form 

 new beds or layers for the propagation of the fungi, the types of which 

 have been described by Mr Hubbard, as follows: one has erect stems with 

 swollen cells at the tips [fig. 105] ; and another forms tangled chains or cells 

 resembling the piled up beads of a broken necklace [fig. 54]. The erect 

 or stem forms occur among species whose larvae live in galleries, such as 

 Platypus and Xyleborus, while the beadlike kinds appear to be peculiar to 



