NEMATODE GALLWORM ON POTATOES, ETC., IN NEVADA. 5 
almost invisible to the naked eye. The mature female is nearly pear 
shaped, as shown in figure 1, being less than a millimeter in length, 
more often about three-fourths of a millimeter long, the body cavity 
being occupied by eggs and lar- 
ve. Themaleisaslender,thread- 
like worm, from 1 to 1.5. milli- 
meters in length (see fig. 2). The 
development of the female takes 
place within the underground tis- 
sues of the host plant and its 
presence in these tissues is indi- 
eated by enlargements or mal- 
formations. Figure 3 shows a 
potato which is badly infected 
with gallworms. The skin is 
roughened and broken in patches. 
Not all infected potatoes show 
Fic. 1.—Female of the nema- 
tode gallworm ( Hetcrodera 
radicicola) magnified 85 di- 
ameters: a, Mouth; b, spher- 
ical sucking bulb; c, c, ova- 
ries, aS seen through the 
body wall; d, anus; e, small 
the same symptoms. Often the 
gallworm is found in potatoes of 
which the skin is nearly smooth, 
and in such cases the presence 
white spots showing approx- 
imately the natural size of 
these worms. They are 
usually white. It is gener- 
ally not difficuit to isolate 
them in water by breaking 
open the galls containing 
them. (After N. A. Cobb.) 
of the parasite can be detected 
only by cutting the potato: In 
the infected tubers there is usu- 
ally a ring of darkened tissue just 
under the skin, and a microscop- 
ical examination of this tissue 
will reveal the presence of the mature females and the 
young larve. Infigure 4 are shown the larve and the 
egos of the gallworm as seen through the microscope 
from a preparation made from a diseased potato. 
One of the eggs seen in figure 4 is shown still further 
enlarged in figure 5. 
LIFE HISTORY OF THE GALLWORM. 
The larvee of the gallworm upon hatching from the 
ego, which hatching sometimes occurs within the body 
of the parent, ultimately escape from the host plant 
and live for a period in the surrounding soil. These 
larvee, although very active, have but little power of 
progressive locomotion, and the spread of infection 
from place to place must depend‘ upon the transporta- 
Fig 2.—The adult 
male of Heterodera 
radicicola, or gall- 
worm: J, Worm 
in profile view; I7, 
head of the same, 
more highly mag- 
nified; J7Z, middle 
region of the worm 
showing blind 
ends of the sexual 
organs; IV, pos- 
terior extremity. 
The drawings 
were prepared 
from stained speci- 
mens, examined 
in carbolic-acid so- 
lution. 
a, Lips; b, cesoph- 
ageal tube; c, medi- 
an bulb; d, excre- 
tory pore; é, spear; 
f, intestine; g, 
blind ends of tes- 
ticles; h, testicles; 
i, spicula; 7, rudi- 
mentary bursa; k, 
anus. (After N. 
A. Cobb.) 
tion of infested soil or infected plants. Soon after emerging from 
the parent and the tissue of the host plant these larve seek other 
[Cir. 91] 
