October 12, 1906.] 



SCIENCE. 



469 



setts, but, because of its thinness, has not 

 heretofore been separated, from the main or 

 drumlin drift (Montauk) and has even failed 

 of recognition where present on the extensive 

 sandy deposits of the Plymouth and Cape Cod 

 regions of Massachusetts. On Long Island it 

 is better developed and is everywhere recog- 

 nized above the older gravels. It is pre- 

 sumably to be correlated with the latest drift 

 of the Mississippi Valley — the Wisconsin. 



M. L. Fuller. 

 United States Geological Suevey. 



food habits of the snail bulimulus dormant 



BINNEY. 



The orange and other Citrus species, several 

 ornamentals, and various greenhouse and other 

 plants are often badly disfigured by the pres- 

 ence of a black saprophytic fungus,^ Meliola 

 Camellice (Catt.) Sacc. commonly known in 

 the orange-growing region of Florida as the 

 * sooty mold ' of the orange. The fungus feeds 

 on a sweet honey dew exuded by various in- 

 sects, especially species of Aphidse, Coccidse 

 and Aleyrodidse. The habits of the Aleyro- 

 didse species are very favorable to the growth 

 of the fungus. This is especially true of the 

 so-called 'white fly' of the orange, Aleyrodes 

 citri. The larvae of this species, attaching 

 themselves to the under surface of the leaves, 

 exude honey dew which, falling to the top sur- 

 face of the leaves and stems beneath supplies 

 nourishment for a heavy growth of the fungus. 

 The white fly and the fungus are invariably 

 associated, and a badly infested grove or hedge 

 may be recegnized at some distance by its 

 heavily coated dark foliage. So dense is the 

 covering of the intertwining hyphse that the 

 smothering layer is believed to interfere seri- 

 ously with the healthy action of the sunlight 

 on the leaves. The fruit as well as the leaves 

 and stems is coated, and a thorough washing 

 of the smutty oranges becomes necessary be- 

 fore marketing; an added expense is thereby 

 incurred as well as increased danger of bruis- 

 ^ Saprophytic in the sense that, although fol- 

 lowing and directly dependent upon various liv- 

 ing insects, sustenance is derived from waste 

 products thrown off from the bodies of these in- 

 sects. 



ing from additional handling and washing, 

 and, unless the oranges are quickly and prop- 

 erly dried, of decay in shipping from the wet- 

 ting. The presence of the sooty mold is thus 

 one of the most serious results of white fly 

 infection of orange groves, and almost the 

 only appreciable injury from this species to 

 privet and other ornamentals, and is an im- 

 portant element in the injury to various plants 

 from numerous other sucking insects. 



The habits of the snail BuUmulus Dormani 

 Binney* are of the greatest interest in this 

 connection. This species, the normal food of 

 which is apparently fungi, algae and perhaps 

 lichens, has been found during the summer of 

 1905 in numerous groves in Manatee County 

 feeding on the sooty mold. The trees on 

 which the snails are found stand out conspicu- 

 ously among the surrounding trees by their 

 bright foliage and fruit, and clean trunks, in 

 contrast to the sooty leaves and. fruit of the 

 surrounding trees. The work of the snails on 

 orange trees is well seen in the Willis grove 

 of the Manatee Lemon Company near Pal- 

 metto, Florida. The trees of this grove are 

 seedlings and reach a height of thirty to 

 thirty-five feet. Snails are present on per- 

 haps seventy-five trees and have completely 

 overrun them from top to base, cleaning the 

 fruit, leaves and trunks. The foliage of the 

 trees not visited by the snails is densely coated 

 by the sooty mold. The snails have not con- 

 fined themselves to the fungus alone, but have 

 freed the trees from algae, and apparently 

 some of the lichens. The snails are even more 

 widely scattered in some of the neighboring 

 groves. The species is evidently native to the 

 Florida Peninsula, having been recorded, ac- 

 cording to Pilsbry, ' Manual of Conchology,' 

 Vol. 12, 1899, from the mouth of the St. Johns 

 Piver south to the Caloosahatchee Eiver. The 

 snails appear to have found their way nat- 

 urally into the groves of ,the Manatee region. 

 Mr. F. D. Waite, manager of the Manatee 

 Lemon Company, observed their presence on 

 one or two trees in the Willis grove as early 

 as the summer of 1903, and they seem to have 

 appeared in other groves at about the same 

 ' Kindly identified for the writer by Dr. W. H. 

 Dall. 



