Page 620 - The Book of Caterpillars: A Life-Size Guide to Six Hundred Species From Around the World

MOTH CATERPILLARS

FAMILY Noctuidae
DISTRIBUTION Across much of United States south of the Great Lakes; Mexico,
Central America, and the Caribbean
HABITAT Meadows and forest edges, as well as disturbed habitat
HOST PLANTS Fruit of Giant Ground Cherry (Physalis peruviana),
Chinese Lantern (Physalis alkekengi), and other Physalis spp.
NOTE Caterpillar with a unique diet that protects it from parasitoids
CONSERVATION STATUS Not evaluated, but common

ADULT WINGSPAN
1 ⁄ –1¼ in (27–31 mm)
CATERPILLAR LENGTH
1½ in (38 mm)
HELIOTHIS SUBFLEXA
SUBFLEXUS STRAW MOTH
618
(GUENÉE, 1852)

The Sub exus Straw Moth caterpillar often feeds in seclusion

within lantern-shaped Physalis fruits, a food resource exclusive
to this species, which has developed a unique ability to mature
on a diet lacking linolenic acid. In other caterpillars, linolenic
acid is necessary for producing a chemical, volicitin, in their
saliva. However, the chemical also triggers the production of
volatiles by the plants on which the caterpillars feed, which are
then detected by parasitoids, enabling them to locate the larvae.
The Heliothis sub exa caterpillar avoids such parasitoid attacks

because of its linolenic-acid-free diet.

The moth and its caterpillar are very similar to a close relative,
the Tobacco Budworm (Heliothis virescens). However, H.
virescens is a significant pest on many different crops, from
soybeans to cotton, while H. sub exa is innocuous. The two

exemplify how a seemingly minor adaptation can radically

change the economic signi cance of an insect species. Heliothis
subflexa is barely known, while the diet of H. virescens costs
millions of dollars a year.

The Sub exus Straw Moth caterpillar is
cryptically colored green with longitudinal dark
stripes, dark spiracles, and black, sclerotized
dorsal verrucae. It has only very few short hairs.
Actual size