121 
These are the only localities where the disease has been found, and 
in both cases it has proved a very effective check. Our facilities have 
not provided for a study of Protozoa, and nothing is known of the 
propagation of this species, either artificially or under natural conditions, 
whether it is a direct or indirect parasite, or whether it can be utilized 
artificially for the control of white-grubs. 
The affected grubs are characterized by their habit of coming to the 
surface of the ground, or near to it, and at a season when, according to 
our observations, the natural migration would be downward, but they 
present no unusual appearance except that they look sickly and emaciated 
and gradually dry up—as one might expect any grub to do if exposed to 
the sun and wind on the surface of the ground where it could not re-enter. 
(Pl. XII, Fig. 48.) 
Bacteria Diseases 
To our knowledge, but one bacterial disease affecting white-grubs 
has been recorded as occurring in this country, although at least two are 
known to attack related species in Europe. Our American disease, due 
to Micrococcus nigrofaciens Northrup, has been studied and described 
by Miss Zae Northrup (52). She concludes that the organism causing 
Fic. 45. A common white-grub (Phyl- 
lophaga sp.) showing typical infec- 
tions of the bacterial disease due 
to Micrococcus nigrofaciens Note 
the one leg with only blackened 
stump remaining; another, in an 
earlier stage, with only its end 
blackened ; also the third infection 
at one of the spiracles. 
the disease is present in soils in widely separated localities in the United 
States and probably through most of the states. The diseased grubs 
are characterized by a blackening of the affected parts (Fig. 45), and an 
excessive wetness of the soil favors the progress of the disease. It has 
been encountered wherever we have collected grubs, and Miss Northrup is 
undoubtedly right in concluding that it is generally distributed through- 
out the United States. According to our observations, grubs become 
infected only through wounds, and the infection is usually limited unless 
certain favorable conditions are present. Grubs are, in fact, often reared 
to maturity which have shown the infection in one or more of their legs. 
We can only conclude from this and other observations, together with 
