In cooperation with Illinois Natural History Survey

Farrar, M.D.

Flint, W.P.

Illinois Digital Environment for Access to Learning and Scholarship Repository

How to Recognize 

Some Common 

Insect Enemies 

of Stored Grain 

By M. D. Farrar and W. P. Flint 
I F the ever-normal granary is to benefit the people of the United States and 
not the insect population, owners of 
stored grain must know how to protect 
it against the onslaught of these destruc­
tive hordes. 
Altho all kinds of stored grains are 
acceptable food to a large number of in­
sects, serious damage to whole grain in 
Illinois bins and cribs is done by only a 
few insects. These can be identified with 
considerable success, even by one rela­
tively unfamiliar with them, by comparing 
them carefully with the pictures and 
descriptions in this circular. 
CONTROL MEASURES 
are given in Circular 486, "How to 
Stop Weevil Damage in Stored Grain." 
Ask for a copy if you do not have one. 
CIRCULAR 497 
UNIVERSITY OF ILLINOIS • COLLEGE OF AGRICULTURE 

AGRICULTURAL EXPERIMENT STATION AND EXTENSION 

SERVICE IN AGRICULTURE AND HOME ECONOMICS 

In cooperation with Illinois Natural History Survey 

A N G O U M O I S  G R A I N  M O T H  

A d u l t  L a r v a  P u p a  D a m a g e  
M o t t l e d  g r a y  F e e d i n g  s t a g e  C h a n g i n g  s t a g e  i n  
T y p i c a l  e x i t  h o l e s  
1 ; ' 4 "  t o  ¥ 3 "  l o n g  
G r a y  t o  w h i t e  
c o r n  k e r n e l  i n  c o r n  k e r n e l  
U p  t o  11 3 "  l o n g  L i g h t  b r o w n  
T h i s  l i g h t - g r a y  m o t t l e d  m o t h  d o e s  m o r e  d a m a g e  t o  e a r  c o r n  i n  
c r i b s  t h a n  a n y  o t h e r  i n s e c t .  I t  a l s o  a t t a c k s  w h e a t ,  r y e ,  a n d  o t h e r  
s m a l l  g r a i n .  T h o  f o u n d  t h r u o u t  I l l i n o i s ,  i t  i s  m o s t  d e s t r u c t i v e  i n  
t h e  s o u t h e r n  h a l f  o f  t h e  s t a t e .  
T h e  e g g s  a r e  d e p o s i t e d  o n  t h e  k e r n e l s  o f  w h e a t  o r  g r a i n s  o f  
c o r n  b y  t h e  a d u l t  m o t h .  T h e  t i n y  w o r m s  ( l a r v a e )  h a t c h i n g  f r o m  
t h e  e g g s  b o r e  i n t o  t h e  g r a i n ,  c o m p l e t e  t h e i r  g r o w t h ,  a n d  g o  i n t o  a  
r e s t i n g  o r  c h a n g i n g  s t a g e  ( p u p a ) ;  t h e n  f i n a l l y  e m e r g e  t h r u  t h e  
h o l e s  t h e y  . e a t  i n  t h e  g r a i n s .  T h e y  e a t  o u t  m o s t  o f  t h e  i n s i d e  o f  
t h e  g r a i n .  A  b r o o d  i s  m a t u r e d  i n  a b o u t  3 5  t o  4 0  d a y s .  I n  s o u t h e r n  
I l l i n o i s  t h e r e  m a y  b e  a s  m a n y  a s  s i x  b r o o d s  a  y e a r .  
C o r n ,  w h e a t ,  a n d  o t h e r  g r a i n s  i n  t h e  f i e l d  a r e  f r e q u e n t l y  
i n f e s t e d ,  a n d  l o s s e s  r u n n i n g  u p  t o  5 0  t o  7 5  p e r c e n t  o f  t h e  v a l u e  o f  
t h e  c r i b b e d  c o r n  a r e  s o m e t i m e s  i n c u r r e d  i n  t h e  c o u r s e  o f  a  s i n g l e  
s e a s o n  i n  t h e  s o u t h e r n  f o u r t h  o f  I l l i n o i s .  
T H E  F I R S T  S I X  I N S E C T S  d e s c r i b e d  i n  t h i s  c i r c u l a r - A n g o U l 2 1 o i s  
g r a i n  m o t h ,  I n d i a n  m e a l  m o t h ,  r i c e  a n d  g r a n a r y  w e e v i l s ,  a n d  t h e  
l e s s e r  g r a i n  b o r e r - a r e  t h e  m a i n  t h r e a t  t o  s t o r e d  g r a i n  i n  I l l i n o i s .  T h e  
o t h e r  f i v e  d o  l i t t l e  d a m a g e  f r o m  f e e d i n g ,  w o r k i n g  m a i n l y  o n  b r o k e n  o r  
c r a c k e d  k e r n e l s  o f  g r a i n ;  b u t  w h e n  p r e s e n t  i n  l a r g e  n u m b e r s  t h e y  m a y  
c a u s e  t h e  g r a i n  t o  h e a t  a n d  m o l d  a n d  t h e r e f o r e  s h o u l d  b e  w a t c h e d .  T h e r e  
a r e  o t h e r  i n s e c t s  t h a t  d o  p r a c t i c a l l y  n o  d a m a g e .  
INDIAN MEAL MOTH 

Adult Larva Damage 
Light brown banded Feeding stage Typical webbing 
with chocolate White to pink in corn kernels 
1/3" to 112" long Up to 1/ 2" long 
This moth is a common and destructive pest of all kinds of stored 
grains as well as soybeans, nuts, dried fruits, and many other food 
products. It occurs thruout the state, laying its eggs on the out­
side of grains. It is easily identified by the dark chocolate­
colored area on the hind part of the wings. 
The young worm (larva) spins a thread of silk wherever it 
goes and webs the food material together. It eats out the inside 
of the grain but does not bore into it. In corn it frequently eats 
out the germ. On becoming full-grown the larva forms a thin 
cocoon, goes thru a changing stage, and emerges as a moth. 
Broods of this moth mature in about 30 to 40 days, and there 
may be as many as four to six broods a year. Under warm 
conditions this insect breeds continuously thruout the year. 
FARMERS WHO FIND in their stored grain insects which they suspect 
of being among the destructive group-the first six described in this cir­
cular":"'-but which they cannot identify with certainty are invited to send 
specimens for identification to: CHIEF ENTOMOLOGIST, ILLINOIS 
NATURAL HISTORY SURVEY, URBANA, ILLINOIS. 
The insects will be examined without charge and a report made on 
which treatment can be based. 
R I C E  W E E V I L  

A d u l t  
A d u l t  
D a m a g e  
B r o w n  t o  b l a c k  
S i d e  v i e w  
C o r n  k e r n e l s  e a t e n  
V a  "  t o  1/ 4 "  l o n g  
o u t  b y  t h e  g r u b  
T h i s  s m a l l  d a r k - b r o w n  s n o u t  b e e t l e ,  s l i g h t l y  s m a l l e r  t h a n  s h o w n  
h e r e ,  i s  t h e  m o s t  c o m m o n  g r a i n  w e e v i l  f o u n d  i n  I l l i n o i s ,  a n d  o n e  
o f  t h e  m o s t  d e s t r u c t i v e .  I t  f e e d s  o n  a l l  k i n d s  o f  g r a i n s ,  p a r ­
t i c u l a r l y  o n  c o r n  a n d  w h e a t .  I t  i s  f o u n d  t h r u o u t  t h e  s t a t e  b u t  i s  
c o m m o n  o n l y  i n  t h e  s o u t h e r n  h a l f .  
T h e  f e m a l e  i n s e c t  m a k e s  a  s m a l l  h o l e  i n  t h e  s i d e  o f  t h e  k e r n e l  
o f  c o r n  o r  g r a i n  o f  w h e a t  b y  b i t i n g  i n t o  t h e  g r a i n  w i t h  h e r  s t r o n g  
j a w s .  S h e  t h e n  t u r n s  a r o u n d  a n d  d e p o s i t s  a n  e g g  i n  t h i s  c a v i t y .  
T h e  f o o t l e s s  g r u b  h a t c h i n g  f r o m  t h i s  e g g  e a t s  o u t  t h e  i n t e r i o r  o f  
t h e  g r a i n ,  c o n s u m i n g  a  l a r g e  p a r t  o f  i t .  W i t h i n  t h i s  c a v i t y  t h e  
g r u b  c h a n g e s  t o  a  r e s t i n g  s t a g e  a n d  c o m e s  o u t  l a t e r  a s  a n  a d u l t  
w e e v i l .  
U n d e r  t h e  m o s t  f a v o r a b l e  c o n d i t i o n s  t h e r e  m a y  b e  a  b r o o d  o f  
t h e s e  i n s e c t s  e v e r y  3 0  d a y s .  I n  s o u t h e r n  I l l i n o i s  b r o o d s  p r o b a b l y  
a v e r a g e  s i x  a  y e a r .  T h e  i n s e c t  h a s  w i n g s  a n d  f r e q u e n t l y  i n f e s t s  
g r a i n  a n d  c o r n  i n  t h e  f i e l d .  
G R A N A R Y  W E E V I L  
O f t e n  a s s o c i a t e d  w i t h  t h e  r i c e  w e e v i l  i s  a  s l i g h t l y  l a r g e r  a n d  
d a r k e r - b r o w n  w e e v i l  w h i c h  a l s o  h a s  a  s h o r t  s n o u t  p r o j e c t i n g  f r o m  
i t s  h e a d .  T h i s  i s  t h e  t r u e  g r a n a r y  w e e v i l .  I t  h a s  m u c h  t h e  s a m e  
r a n g e  a n d  l i f e  h i s t o r y  a s  t h e  r i c e  w e e v i l  a n d  l i k e w i s e  c a u s e s  
s e r i o u s  d a m a g e .  T h e  a d u l t  c a n n o t  f l y  a n d  d o e s  n o t  i n f e s t  g r a i n  
i n  t h e  f i e l d s .  
LESSER GRAIN BORER 

Adult Adult 	 Damage 
Brown Side view Wheat kernel completely
Vs" long 	 destroyed 
This small cylindrical brown beetle, shown here about twice its 
actual size, is one of the most destructive of all the beetles feed­
ing on stored grains. Both adults and young feed on the interior 
of the grain. Where infestation occurs, immediate steps should 
be taken to clean it up. 
In the northern half of Illinois this insect is not so generally 
distributed as are most of the common grain-infesting insects. 
Four to six broods a year may be produced. 
CADELLE 
Adult 	 Feeding stage 
Black, 112" long 	 White tipped with black 
Up to~" long 
This rather large black beetle is only of moderate importance as 
a grain pest in Illinois. It is usually associated with the other 
grain-infesting insects; and while it may become abundant enough 
to do considerable damage, it will not of itself usually require 
fumigation. 
The adult female usually lays her eggs on the grain next to 
the bottom and sides of the bin. The white, black-headed larvae 
feed on the outside of the grain, never boring into it. In wooden 
bins or cribs they frequently bore into the wood, especially where 
it is soft or doty. 
M E A L W O R M S  

Y e l l o w  m e a l w o r m  
L i g h t  b r o w n  
F e e d i n g  s t a g e  U p  t o  1 "  l o n g  
W h i l e  c o m m o n  t h r u o u t  I l l i n o i s ,  m e a l w o r m s  a r e  o f  s e c o n d a r y  
i m p o r t a n c e  a s  g r a i n  p e s t s .  T h e y  a r e  o f t e n  f o u n d  i n  s t o r e d  w h e a t  
o r  s h e l l e d  c o r n  b u t  a r e  o f  l i t t l e  i m p o r t a n c e  i n  c r i b s  o f  c o r n .  
T h e s e  w o r m s  c l o s e l y  r e s e m b l e  w i r e w o r m s  i n  a p p e a r a n c e .  T h e y  
f e e d  o n  t h e  o u t s i d e  o f  t h e  g r a i n ,  b e i n g  t o o  l a r g e  t o  b o r e  t h r u  i t .  
T h e  b l a c k  a d u l t  b e e t l e s  a l s o  f e e d  o n  t h e  g r a i n .  T h e r e  i s  p r o b a b l y  
n e v e r  m o r e  t h a n  o n e  b r o o d  a  y e a r .  
S A W - T O O T H E D  G R A I N  B E E T L E  
A d u l t  
B r o w n
~ 
1 / s "  l o n g  
T h i s  t i n y  b r o w n ,  v e r y  a c t i v e  b e e t l e ,  s h o w n  h e r e  a b o u t  t w i c e  i t s  
a c t u a l  s i z e ,  i s  n o t  a  p r i m a r y  f e e d e r  o n  w h o l e  o r  u n d a m a g e d  g r a i n ,  
b u t  c h o o s e s  c r a c k e d  a n d  b r o k e n  k e r n e l s .  B o t h  a d u l t s  a n d  l a r v a e  
f e e d  o n  t h e  d a m a g e d  k e r n e l s .  B i n s  o f  o a t s  a n d  b a r l e y ,  s h e l l e d  
c o r n ,  a n d  l e s s  f r e q u e n t l y  w h e a t ,  a r e  i t s  p r i n c i p a l  f e e d i n g  g r o u n d .  
W h e n  p r e s e n t  i n  l a r g e  n u m b e r s ,  t h e s e  i n s e c t s  m a y  c a u s e  t h e  g r a i n  
t o  h e a t ,  a n d  i t  i s  t h i s  t h a t  m a k e s  t h e m  a  t h r e a t  t o  s t o r e d  g r a i n .  
T h e  l a r v a e  a r e  s m a l l ,  t h r e a d - l i k e  w o r m s  a b o u t  Y 4  i n c h  l o n g  
w h e n  f u l l - g r o w n ,  a n d  t h e y  a r e  f o u n d  t h r u o u t  t h e  g r a i n  w h e r e  t h e  
a d u l t s  o c c u r .  
T h i s  b e e t l e  i s  a b o u t  a s  c o m m o n  i n  n o r t h e r n  a s  i n  s o u t h e r n  
I l l i n o i s .  I n  t h e  w a r m e r  p a r t s  o f  t h e  s t a t e  i t  b r e e d s  t h r u o u t  t h e  
y e a T ,  p r o b a b l y  a v e r a g i n g  t w o  o r  t h r e e  b r o o d s .  
T u r n i n g  t h e  g r a i n  o r  m o v i n g  i t  w i l l  u s u a l l y  c o n t r o l  t h i s  i n s e c t ;  
b u t  w h e r e  i n f e s t a t i o n  i s  h e a v y  e n o u g h  t o  c a u s e  h e a t i n g ,  f u m i ­
g a t i o n  m a y  b e  n e c e s s a r y .  
CONFUSED FLOUR' BEETLE 

Adult Feeding stage 
Reddish brown Light brown 
1,4" long Up to 113" long 
This small mahogany-brown beetle is one of the most common 
insects wherever grain is stored in elevators, mills, bins, or cribs, 
but fortunately it causes very little damage. Both the beetles and 
their grayish-colored larvae feed principally on the outside of 
cracked or broken grain. Two to four broods mature each year. 
Turning the grain will usually control this insect. Generally 
known as "bran bugs," confused flour beetles do more damage in 
ground feed than in grain stored whole. 
FLAT GRAIN BEETLE 
Adult 
Light brown 
1116" to ~8" long 
This tiny flat brown beetle, shown here about twice its actual size, 
infests all kinds of grain and grain products. It is of secondary 
importance in stored grain. It feeds on cracked grains or broken 
kernels, not on the entire kernel; and both adults and their small 
worm-like larvae always feed on the outside of the grain. 
This beetle occurs thruout the state, but is rarely of enough 
importance to warrant fumigation. 
C A R P E T  B E E T L E S  
F e e d i n g  s t a g e  
F e e d i n g  s t a g e  
D a r k  b r o w n  
B r o w n  
U p  t o  1 / 2 "  l o n g  
U p  t o  l / a "  l o n g  
S e v e r a l  k i n d s  o f  s m a l l  g r a y - t o - b r o w n ,  d i s t i n c t l y  h a i r y  w o r m s  m a y  
b e  f o u n d  i n  s t o r e d  g r a i n  o r  g r a i n  p r o d u c t s ,  e s p e c i a l l y  i n  w h e a t .  
T h e s e  a r e  t h e  y o u n g  o f  s o m e  o f  o u r  c o m m o n  D e r m e s t i d  b e e t l e s  o r ,  
a s  t h e y  a r e  c a l l e d  w h e n  w e  f i n d  t h e m  i n  o u r  h o u s e s ,  c a r p e t  b e e t l e s .  
T h e s e  b e e t l e s  f e e d  o n  a  w i d e  v a r i e t y  o f  f o o d  a n d  a n i m a l  p r o d u c t s  
a n d  o c c u r  i n  a l l  p a r t s  o f  I l l i n o i s  i n  a b o u t  e q u a l  n u m b e r s .  
O c c a s i o n a l l y  t h e s e  b e e t l e s  b e c o m e  n u m e r o u s  e n o u g h  i n  o l d  
g r a i n - g r a i n  t h a t  h a s  b e e n  h e l d  o v e r  f o r  s e v e r a l  s e a s o n s - t o  
w a r r a n t  f u m i g a t i o n ,  b u t  u s u a l l y  t h e y  a r e  o f  s e c o n d a r y  i m p o r t a n c e .  
T h e  l a r v a e  f e e d  o n  t h e  o u t s i d e  o f  t h e  g r a i n .  A d u l t s  f e e d  o n  t h e  
p o l l e n  o f  f l o w e r s  a n d  a r e  n o t  o f  a n y  i m p o r t a n c e  a s  g r a i n  p e s t s .  
P A R A S I T E S  O F  S T O R E D - G R A I N  I N S E C T S  
A d u l t  
B l a c k  
1 A 6 "  t o  1, 8 "  l o n g  
T h e r e  a r e  s e v e r a l  k i n d s  o f  t i n y  w a s p s  t h a t  a t t a c k  a n d  d e s t r o y  
s t o r e d - g r a i n  i n s e c t s ,  p a r t i c u l a r l y  t h e  l a r v a e  o f  t h e  t w o  g r a i n  
m o t h s  ( p a g e s  2  a n d  3 ) .  O n e  o f  t h e s e  w a s p s  i s  i l l u s t r a t e d  h e r e  
m a g n i f i e d  t o  a b o u t  t w i c e  i t s  a c t u a l  s i z e .  
F a r m e r s  c a n  b e  g l a d  w h e n  t h e y  f i n d  t h e s e  w a s p s  i n  t h e i r  s t o r e d  
g r a i n ,  f o r  i t  m e a n s  t h a t  t h e r e  w i l l  b e  l e s s  d a m a g e  f r o m  d e s t r u c t i v e  
i n s e c t s .  
T h e s e  w a s p s  a r e  s t r o n g l y  a t t r a c t e d  t o  l i g h t s  a n d  a r e  f r e q u e n t l y  
t o  b e  s e e n  o n  t h e  w i n d o w s  o f  c r i b s  o r  b u i l d i n g s  i n  w h i c h  g r a i n  i s  
s t o r e d .  
P r i n t e d  i n  f u r t h e r a n c e  o f  t h e  A g r i c u l t u r a l  E x t e n s i o n  A c t  a p p r o v e d  b y  C o n g r e s s  M a y  8 ,  1 9 1 4 .  
H .  P .  Rus~ D i r e c t o r ,  E x t e n s i o n  S e r v i c e  i n  A g r i c u l t u r e  a n d  
H o m e  	 E c o n o m i c s ,  U n i v e r s i t y  o f  I l l i n o i s  
U r b a n a ,  N o v e m b e r ,  1 9 3 9  1 1 - 3 9 - 1 S M - 1 7 7 4 5  


How to recognize some common insect enemies of stored grain

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How to recognize some common insect enemies of stored grain

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