May s 1923 
407 
Striped Sod Webworm 
THE LARVA 
HABITS 
The larva of mutahUis is one of the easiest to recognize in the field. 
The distinct striping of the body and the prominent dark markings of 
the head distinguish it. When newly hatched the head and cervical 
plate are shining jet black ^ and the body pale grayish yellow except 
for the spot of color in the intestinal tract, due to the bit of eggshell 
eaten in leaving the egg. The pinacula are dusky and unusually con¬ 
spicuous for the first instar. During the first three instars the head 
remains black or very deep fuscous. In the fourth and succeeding 
instars it becomes brownish yellow, marked in a definite pattern with 
close groups of small, round, dark brown or black spots. 
In the writer’s experiments many larvae were reared on blue grass, 
small sods of which were potted and covered with lantern globes. The 
newly hatched larvae begin to feed by cutting small pits between the 
vascular bundles on the upper surface of the leaf blade, usually toward 
the base. These pits are spon covered with a few silk fibers, and shortly 
the larva is concealed by excrement placed systematically in this web¬ 
bing. During the first three instars, only the green leaf tissue is con¬ 
sumed, leaving the lower epidermis intact; thereafter the entire thick¬ 
ness of the leaf is eaten. As soon as the larva becomes too large to 
remain sheltered on the leaf blade it descends to the ground and makes 
a burrow lined with silk and opening usually close beside the stem. In 
the field there is often a valve-like arrangement at the tip of this tube, 
so that the larva from within can close it and remain secure from intru¬ 
sion. Beneath the surface the burrow may run at almost any angle. 
If the earth is soft it frequently is parallel with and close beside the main 
stem of the plant; if the ground is hard, it may run off at right angles 
just beneath the surface. The upper part of the tube is rather substan¬ 
tially constructed and closely lined with silk. Farther down the silk is 
more sparingly used and often just above the lower end ceases altogether, 
leaving only the earthen walls. The extreme lower end is again lightly 
lined with silk. This peculiar construction serves a very useful purpose in 
protecting the larva. When the plant is disturbed the larva instantly 
retreats to this silk-lined extremity of its burrow. If the plant and 
burrow be dug or pulled from the ground the tube breaks at its weakest 
point. The larva draws the earth-covered silk lining tightly about itself 
and so closely resembles a mere lump of earth that surprisingly often it 
escapes further detection. These larvae become very large and brightly 
colored and but for the protection of this bit of webbing would be the 
most easily discoverable of the webworms. 
Although in the cornfield the burrow often runs into the ground close 
by the stem of the plant, very little if any feeding is done beneath the 
surface. Quite unlike caliginoselluSy which occupies a half-cylindrical 
tube lying against the stem and feeds exclusively underground, mutahilis 
always has an exit to the outside and feeds aboveground. The leaves 
are eaten, beginning at the base, and as they are cut fall away from the 
plant and lie wilting on the ground. Sometimes so many leaves are 
cut in this way that to obtain green food the larva is forced to consume 
* Felt’s {4, p. 65) surmise as to variations in the color of the head of the newly hatched larva is clearly 
an error, for the head colors of the first instar of the various species are remarkably constant. 
