54 J. PERCY BAUMBERGER 



tip. The latter condition is termed conidial by Hubbard. 

 Escherich observed that these conidia served as food for the 

 beetles and their larvae. As a certain degree of moisture is re- 

 quired by the fungus, the insects never select dried-out trees for 

 their galleries, but always bore in wood which retains some sap. 

 Other species of ambrosia beetles (Corthylus) are able to live in 

 sapwood in the absence of the fungus, perhaps because of the 

 abundance of protein in that region. The fungus is usually prop- 

 agated in a little bed of chips, prepared by the female, in which 

 the egg is deposited. In other species the woody tissue, after 

 passing through the digestive tract of the larvae, has a yellow 

 mustard color. In this condition it is plastered on the walls of 

 the gallery and serves as a medium on which fungus grows. Un- 

 doubtedly, under these conditions the fungus may be considered 

 as a chemical collaborator digesting food indigestible to the in- 

 sect and furnishing it in a tender luscious form to the larvae. 



Hedgcock ('06) studied fungi from various species of Ambrosia 

 beetles and was able to refer them to the wood-bluing (Cerato- 

 stomella), wood-blackening and -browning (Grophium, Hormo- 

 dendron, and Hormiscium) and to the wood-reddening (Penicil- 

 lium and Fusarium fungi. According to Escherich and Neger, 

 the fungus in the absence of the larvae may assume a slightly dif- 

 ferent form. Neger has also found fungi in the galleries of Ce- 

 rambyx and Tetropium luridum, but is unable to decide whether 

 or not it serves as food. 



The fungus-growing habits of the white ants or termites are 

 principally known through the work of Hagen ('60), Holte ('99), 

 Haviland ('02), Triigardt ('04), Doflein ('05, '06), Fetch ('06), 

 and many others. These wood-eating insects build subterranean 

 nests, the ground which they excavate being placed in a pile 

 which itself is later used to form chambers. Shafts may be left 

 in this superstructure with an outer chimney; these are used as 

 permanent scaffolds and have little effect on the ventilation of the 

 nest. The fungus gardens are either on the floor or suspended 

 from the ceilings of the chambers, and consist of a mass of com- 

 minuted woody tissue which has passed through the digestive 

 tracts of the workers and is then built into the comb. The fun- 



