ON CERTAIN PECULIAR FUNGUS-PARASITES OF 



LIVING INSECTS 1 



Roland Thaxter 



(with plates xvi-xix) 



During the past ten years the writer has examined many 

 thousands of freshly collected insects of various sorts preserved 

 in alcohol, which have come from various parts of the world, 

 especially from tropical regions, and in looking them over for 

 fungus-parasites, the possibility of encountering forms which might 

 throw some light on the origin of the Laboulbeniales, yet not mem- 

 bers of this group, has been constantly in mind. Although the 

 hope of meeting with forms of this nature has not been realized, 

 and nothing remotely related to these plants has been seen, apart 

 from many genera and species which are entirely typical of the 

 group, a certain number of wholly unrelated fungi have been 

 observed, which appear to be as peculiar in their mode of life on 

 living insects as are the Laboulbeniales themselves. Although 

 few in numbers, these parasites belong to several quite unrelated 

 groups, and seem to have adjusted themselves successfully to the 

 uncertain conditions of life and propagation on rapidly moving 

 living hosts. The apparent rarity of most of them seems quite 

 remarkable, however, in view of the fact that any such exist; 

 since, if a certain small number of insects furnish favorable condi- 



elopment, it is difficult 



similar 



parasitized, 



and why an extensive flora of this nature, or at least one comparable 

 in numerical importance to that of the Laboulbeniales, has not 

 been developed. 



What may be called the idiosyncracies of such parasitism are 

 well illustrated by equally inexplicable host relations or rather 

 lack of host relations, between certain groups of insects and the 

 Laboulbeniales. The ants, for example, would seem from their 



1 Contributions from the Cryptogamic Laboratories of Harvard University, 



LXXIV. 



2 35l [Botanical Gazette, vol. 58 



