16 BULLETIN 892, U. S. DEPARTMENT OF AGRICULTURE. 
In 1906 Prof. R. A. Cooley (13) mentioned attack to beets at Bill- 
ings, Mont. . 
In 1912 and in 1918 summarized popular economic accounts were 
published by Messrs. Sanderson (14, p. 337-339) and Crosby and 
Leonard (15, p. 95-96). 
NATURAL ENEMIES. 
LADYBIRD BEETLES. 
Fortunately the beet leaf-beetle has a goodly number of natural 
enemies. Among the most useful are the convergent ladybird (Hip- 
podamia convergens Guér.), the sinuate ladybird (ZZ. sinuata Muls.), 
and the glacial ladybird (Z. glacialis Fab.). These ladybird beetles 
do considerable good by destroying the eggs of the overwintered 
leaf-beetles. Occasionally the ladybirds nearly “ wipe out” the eggs 
which are deposited on certain areas during April and May. A case 
of this kind was noted during the spring of 1911. On a neglected 
spot of alkali soil about an acre and a half in extent which had been 
undisturbed for three years and was covered with a rank growth of 
“tickle grass” and weeds, the leaf-beetles had hibernated in large 
numbers. With the advent of warm weather the following spring 
an abundant supply of Russian thistle, lambs’-quarters, sea purslane, 
and sea-blite sprang up and the conditions promised to be ideal for 
the production of an enormous first generation of the beet leaf-beetle. 
As soon, however, as egg laying began, the ladybirds began their 
good work, continuing it through April and May and into June, or 
until the majority of the overwintered beetles had died or scattered 
to other quarters. Only a very few leaf-beetle larve of the first 
generation developed on this area. 
As previously noted, the beet leaf-beetle hibernates on compara- 
tively restricted areas. The ladybirds, however, enjoy a much wider 
range and hibernate under weeds, grasses, yucca plants, and rubbish 
wherever convenient shelter is found. Being thus widely scattered, 
it frequently happens that the ladybirds occur in comparatively 
small numbers on the areas where the leaf-beetles are ovipositing, 
and there are always some eggs which escape destruction. 
The ladybirds eat the eggs of the beet leaf-beetle practically 
throughout the season but by far the greater number are destroyed 
during the spring at a time when aphids and other soft-bodied insects 
are less plentiful. The ladybirds simply utilize the leaf-beetle eggs 
as a convenient supply to tide them over from the time of emergence 
from hibernation until aphids become abundant, which is not strange, 
as the leatf-beetle eggs have tough shells and are consequently more 
difficult to eat than aphids. 
sj 
