INTRODUCTION
The Indianmeal moth was given its common name by an early American entomologist
(Asa Fitch) who found it feeding on cornmeal (Indian meal). It is probably
the most important and most commonly encountered pest of stored products
found in the home and in grocery stores in the United States. Of Old World
origin, it is now found worldwide.
RECOGNITION
Adults with wingspread (wing tip to wing tip) about 5/8-3/4? (16-20 mm).
Wings pale gray but front wing with outer 2/3’s reddish brown with
a coppery luster.
Mature larva usually
about ½” (range 9-19 mm) long. Usually dirty white but color
may vary to a greenish or pinkish or brownish hue depending on its food,
with head and prothoracic plate/shield yellowish brown to reddish brown.
With 5 pairs of well-developed prolegs on abdomen and each bearing crochets
(hooks). Prespiracular tubercle (wartlike area between spiracle and front
edge of segment) of prothorax with 2 setae (hairs). Tubercle VI on mesothorax
(wartlike area near and above leg) with 1 seta (hair). Body without pinacula
(dark or pale wartlike area at base of hairs or setae) on mesothorax,
metathorax, and 1st 9 abdominal segments. Rim around spiracles of about
even thickness.
SIMILAR GROUPS
(1) Carpet/tapestry moth (Trichophaga tapetzella) with basal 1/3 of front
wing dark down to black, remainder of wing white mottled with gray and
black.
(2) Other small
moths lack front wing with basal 1/3 pale and remainder dark, wing span
of about 5/8-3/4” (16-19 mm), and /or hind wing broader than front
wing and fringed with long hairlike scales.
BIOLOGY
Chiefly at night, the female lays 100-400 eggs, singly or in small groups,
on the larval food material during a period of 1-18 days. Upon hatching,
the larva establishes itself in a crevice of the food material. It feeds
in or near a tunnellike case it has webbed together of frass and silk.
The larval period lasts 13-288 days, depending primarily on temperature
and food availability. When the last instar larva is ready to pupate,
it leaves the food and wanders about until a suitable pupation site is
found. There are usually 4-6 generations per year (range 4-8), with the
life cycle (egg to egg) typically requiring 25-135 days (range 25-305).
HABITS
The adults cause no damage. The larvae are surface feeders and generally
produce a lot of webbing throughout the infested part of materials. They
are general feeders and attack grain products, a wide variety of dried
fruits, seeds, nuts, graham crackers, powdered milk, biscuits, chocolate,
candies, dried red peppers, dry dog food, and bird seed. They are very
destructive wherever dried fruits are stored. Preferred are the coarser
grades of flour such as whole wheat, graham flour, and cornmeal, but they
can breed in shelled or ear corn.
When the larvae wander about looking for pupation sites in homes, they
are often mistaken for clothes moth larvae. Likewise, when the moths are
flying, they are also mistaken for clothes moths.
Adults are attracted
to light.
CONTROL
Follow the standard control procedures for stored product pests but remember
that pupation takes place away from the infested food material.
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