a9) 
disease was not found elsewhere. August 19, 1915, the writer was in- 
formed by Mr. Frank S. Turner, a farmer living a mile east of Lancaster, 
that the grubs seemed to be dying in one of his fields where they had 
destroyed most of the corn that summer. An examination showed 
that a third or more of them were dead and yellow or decayed, and by 
October 5 at least 90 per cent. of the grubs had died. The disease was 
also prevalent in neighboring fields to a distance of three-fourths of a 
mile to a mile. With one exception, every field in which the dying grubs 
were found had been in timothy the year before, that is, the year the 
beetles were abundant, but whether this had any significance other than 
that such land is usually the worst infested with grubs, can not be told 
at this time. The one exception was a corn field which was in oats the 
previous year and adjoined a field which contained diseased grubs. 
According to Mr. Turner’s observations the disease made its appearance 
in a very wet spell about the first of July, and five or six weeks later, 
when the writer visited the field, a third of the grubs had been killed. 
Towards the end of August and following a period of wet weather 
newly affected grubs again became numerous, but shortly after this a 
dry spell seemed to retard the spread of the disease. From these 
Fic. 44, Nematodes found infesting white-grubs: a, mature indivdiual ; 
b, immature worm. 
observations it seems likely that moisture plays an important role in the 
occurrence, abundance, and spread of this nematode infestation. Af- 
fected grubs were usually within six inches of the surface. They have 
a characteristic appearance (Pl. XII, Fig. 49), recently killed grubs 
being of a peculiar lemon-yellow color and the body fluids yellowish 
green. A few days or a week later they begin to take on a brownish 
color, due apparently to decay, and several weeks after the death of the 
grub decay and disintegration is complete. The bodies of the dead 
grubs are filled with thousands of small nematodes, and frequently, with 
the aid of a magnifier, the active parasites are plainly visible through 
the skin of the host. The appearance of the nematode as it occurs in 
the grub, is shown in Figure 44. Individuals which appeared mature 
measured 2.17 mm., the smaller ones measuring .39 to 1.00 mm., and the 
average being approximately .80 mm. 
Grubs were sent to Dr. N. A. Cobb, who found two species present, 
one being Diplogaster aerivora Cobb, and the other immature Cephalo- 
bus (?) sp., the primary affection being considered by Dr. Cobb as due 
to the Diplogaster, although this point was not positively determined. 
An account of the life history and habits of D. aerivora has been pub- 
