June, *18] 
BURGER AND SWAIN: WALNUT APHIS, FUNGUS 
287 
were examined from time to time as they were found, and without any 
exception they were infected with this same Entomophthora. 
Description of the Fungus 
During the spring of the year and in places where the humidity is 
rather high due to the fogs, an Entomophthora is parasitic upon the 
walnut aphis, Chromaphis juglandicola (Kalt.). The disappearance 
of this insect during the summer months was always thought to be due 
to heat and predaceous insects. Only one record has been found where 
a fungus was responsible for the control of this pest. 1 The writers have 
been unable to learn whether or not this was the same fungus as that 
herein described. 
This fungus attacks the aphid in all its stages of growth from the 
mature winged form to the small first instar larva. One of the first 
signs of parasitism of the insect is the sluggish movement of the in¬ 
dividual attacked. Later the body turns a darker yellow and is 
somewhat swollen. Then from the body of the dead aphid the small 
hyphse begin to protrude, which in due time form a white fringe about 
the body (pi. 9, fig. 1). In some cases the protruding hyphse are in 
such numbers that the insect looks like a white, glistening, spherical 
mass, which later turns a light brown in color. When the bodies of 
the insects are crushed and placed under the microscope, they are 
seen to be filled with large septate anastomosing hyphse. These mum¬ 
mified bodies remain for some time, hanging ,to the leaves by means of 
haustoria until removed by some external agency. 
The spores of the fungus are bell-shaped with a sharply pointed 
apex (pi. 9, fig. 2). These spores are borne on a club-shaped conidio- 
phore. When the spore is mature, it is shot from the conidiophore 
with considerable force. Clinging to the spore is a mass of proto¬ 
plasm that glues it to any object which it happens to strike. If the 
object happens to be the body of an insect, the spore germinates and 
the germ tube penetrates the insect. If, however, the spore happens 
to strike an unfavorable object for its growth, it again forms a secon¬ 
dary spore (pi. 9, fig. 3), which is much smaller but is ejected in the 
same manner, and the process is repeated until the spore either is 
exhausted or finds a suitable host. On the wings and legs of the 
affected insects could be seen many of the discharged spores imbedded 
in a cushion of protoplasm. Many of these spores had germinated 
and produced the secondary spores. 
Some of the dead aphids were black and were thought to be attacked 
1 Davidson, W. M. Walnut aphids in California. U. S. Dept. Agr., Bull. 100, 
page 35, 1914. 
