133 
THE CONTAGIOUS DISEASES OF THE WHITE GRUBS. 
The native contagious diseases of the American white grubs 
are not, so far as known, encouraging subjects for practical use 
in the destruction of these insects; but certain other insect dis¬ 
eases, due to parasitic fungi capable of artificial cultivation, offer 
a more promising resource. Numerous experiments have been 
made in recent years in France with a native fungus parasite* 
of the European larva of Melolontha vulgaris (already fre¬ 
quently referred to as the agricultural equivalent of our species) 
which have been carried so far by Prof. A. Giard as to lead to 
the artificial cultivation of this fungus on a large scale, and its 
sale to farmers as a specific for that insect. 
Experiments with this fungus for the destruction of larvae of 
Lachnosterna and allied American genera were made in my lab¬ 
oratory in 1892, and similar and still more extensive experi¬ 
ments were made with two other species ( Isaria leprosa and 
Sporotrichum globu life rum) occurring spontaneously in America. 
This work was done under my own immediate supervision by an 
assistant, Mr. John Marten, from whose report I take the fol¬ 
lowing statement of methods and results: 
Two culture tubes of Botrytis tenella were obtained in 1892 
from a Parisian firm of chemists, who offered the spores of this 
fungus in glass tubes for sale; and another was received directly 
from Professor A. Giard. March 31, 1892, fifty grubs taken 
from a rotten oak log—most of them Polymoechus brevipes and 
the remainder Serica vespertina —were thoroughly dusted with a 
portion of the contents of one of these tubes, and were then 
placed in an earthen dish with a quantity of the rotten w T ood. 
A check lot was established under similar conditions, but not 
dusted with the spores. The first effect of this treatment was 
observed April 6, w T hen a single larva each of Serica and Poly¬ 
moechus was found dead, the latter with flabby thorax and the 
abdomen somewhat hard. This lot of larvae was examined at 
intervals of two days, and April 8 one more was found dead, April 
10 sixteen, on the 12th seventeen, on the 14th one, on the 16th 
three, on the 18th four, and, finally, May 2 sixteen more—mak¬ 
ing forty-nine in all. 
Infection by this fungus is unmistakably indicated by a pale 
pink tint of the dead larva, deepening to a definite rosy color, 
which disappears, however, with the development of spores upon 
the surface of the grub. This characteristic color w'as shown by 
twenty of the above larvae, the first exhibiting it April 8. It 
was noticed that the Serica larvae, although seemingly affected 
like the others, did not change color in this way. An external 
*Botrytis tenella or Isaria densa, as it is variously called by different authors. 
