347 



the conditions under which a parasitic fungus attacks a new host 

 species, nothing" appears to be known in the tropics, since the 

 records as a rule do not go back far enough to show that when a 

 parasitic fungus is found on an apparently new host plant, it has 

 never actually occurred on that host before in the same locality, 

 or in some other. This again is a problem worthy of attention. 



Other problems of some economic importance also occur in 

 connection with the life-histories of fungi, besides those men- 

 tioned by Professor Salmon. One is: to what extent a strain of a 

 parasitic fungus may lose its virulence when growing for some 

 time on the same host plant in a limited area, exhibiting fairly 

 uniform conditions of climate. Another is : to what extent do 

 strains showing very marked differences in virulence occur in one 

 species of parasitic fungus. While yet another is : to what extent 

 do certain species of partly parasitic fungi, such as Thyridaria 

 tarda, found throughout the tropics on several host plants and 

 originally probably pure saprophytes, exhibit before our eyes a 

 process of developing parasitism, becoming at the same time spe- 

 cialized to the host plant predominating in any given locality. 

 So many partly parasitic fungi are of universal distribution in the 

 tropics, and are capable of attacking several host plants, that it 

 seems very possible that some of them may actually afford- in- 

 stances of the progress and specialization of parasitism. 



The investigation of problems of the nature of those just con- 

 sidered belongs in a sense to the realm of pure research, and re- 

 quires more time than is usually available to the plant pathologist 

 engaged in pioneer or routine work. In fact such investigation 

 bears much the same relation to routine plant pathology that medi- 

 cal research does to the work of a general practitioner. The 

 future may prove that the parallel can be carried farther, and that 

 the solution of these problems is as important to the economic 

 welfare of an agricultural community as the results of medical 

 research are to its bodilv health. 



A SUGAR-CANE PEST IN ST. CROIX. 



Dr. Longfield Smith, Ph. D., Director of Agriculture, St. Croix, 

 Danish West Indies, in correspondence with the Imperial Com- 

 missioner of Agriculture, has given a brief account of an insect 

 which occurs in that island as a pest of atigar-cane. 



The insect is a large, brown beetle, the name of which Dr. 

 Smith gives as Sfratcgiis titanus ; it belongs to the same family as 

 the common hardback (Liv;ynis titiiiulosus). The larva of Strafe- 

 gns titanus is in shape and general appearance similar to the typi- 

 cal larvae of insects in this group, but it is much larger than the 

 common hardback larva, attaining a length of over 2 inches, while 

 it is about one-lialf inch in thickness. 



The insects of this group. Dynastides. are more often scaveng- 

 ers, feeding on decaying organic matter, than actual pests feeding 



