THE BIOGRAPHY OF A BEETLE
By Fred H. Arnold,
Regional Forester.
In common with most of the destructive tree insect
pests in the United States the Japanese beetle is of exotic orgin. Its
native home is Japan, hence the name by which it is commonly known.
Entomologists speak of this "bug" as Popillia Japonica. First
discovered in this country near Riverton, N. J., in 1916, it since has
thrived and spread throughout southern and central New Jersey, eastern
Pennsylvania, and northern Delaware. Beyond this area the beetles have
been found from New England to South Carolina and as far west as
Missouri. Despite strict quarantine regulations enforced by the U. S.
Department of Agriculture and other efforts to check it, the beetle
appears to be increasing gradually in numbers and widening its
geographical distribution.
There are four stages in the life history of this
destructive pest, namely; the adult (beetle), egg, larva (grub), and
pupa. Anyone who has seen the adult beetle will not soon forget its
striking appearance. It has a lustrous metallic green color with a
bronze sheen on the wing covers. Broadly oval in shape it is slightly
less than one-half inch long and one-fourth inch wide. The eggs are
between one-sixteenth and one-eighth inch long, elliptical to nearly
spherical, and of a creamy white color. The typically curled larva
varies in length up to an inch, with a white body that is bluish within,
and with a light brown head. About the size of the adult and resembling
it somewhat, the fully developed pupa is tan in color and elliptically
shaped.
Depending upon the advance of the spring season and
varying with latitude and elevation, the adult beetles emerge from the
soil during June and July. Immediately they begin to feed upon plant
leaves and flowers, having voracious appetites. They habitually mass
themselves in dense clusters on certain individual plants which are thus
heavily fed upon, while seemingly ignoring other nearby plants of the
same kind. As many as 296 beetles have been found massed upon a single
apple. The adults are short-lived, averaging one month to a month and a
half of life as herbivorous gourmands. They feed and fly about most
vigorously on warm, sunny days and similarly during the warmer part of
the day, between 10 A.M. and 3 P.M. Early in the morning and late in the
afternoon they feed on the lower plants, and during the middle of the
day when they are most active they are likely to be found seeking food
on the higher trees. The beetles are relatively in active on cloudy or
cool days. By late August most of the adults have dies, their bodies
lying on the ground beneath the badly mutilated host plants. Late
individuals occasionally may be found flying about until October since
all do not leave the soil at the same time.
Egg-laying begins soon after emergence, the females
burrowing a few inches into the soil and depositing one to four eggs at
a time. Another group of eggs may be laid after a day or two of feeding,
and this program is repeated until mid-August by which time each female
has deposited between 40 and 60 eggs. Both male and female beetles
continue to feed ravenously from the time of their emergence until
death.
The eggs require only about two weeks to hatch after
they are laid. The resultant grubs feed upon the finer roots in the
soil, particularly those of grasses, legumes, and of certain flowers and
garden vegetables. Extensive patches of lawns may be killed as a result
of this injury. During this feeding period the larvae work within the
upper three inches of the soil, but with the approach of winter they
burrow deeper and spend the winter in an inactive state at depths of
from four to eight inches below the surface. With the rising of soil
temperatures in the spring the larvae move upward and again feed on
roots between April and June. During May or June they are transformed to
the pupal stage which is a dormant condition lasting from one to three
weeks depending upon the climate and other local conditions. Pupae then
are transformed into adult beetles which in turn emerge from the soil
and the life cycle is thus complete.
The Japanese beetle is known to feed upon a great
variety of plants. Nearly 300 different species of non-evergreen trees,
shrubs, and flowers are eaten by the adult beetles with varying degrees
of preference. Certain species, such as apple peach, plum, cherry,
grape, rose, elm, horse chestnut, sassafras, willow, basswood,
raspberry, blueberry, dahlia, hibiscus, hollyhock, and zinnia, are
highly susceptible to attack by the insect and are heavily damaged by
it. Other plants, however, are relatively resistant to it and are only
seldom attacked. Some of these more or less immune plants are
evergreens, including rhododendron and azalea, ash, beech, most of the
oaks and maples, honeysuckle, redbud hydrangea, lilac, privet,
forsythia, peony, petunia, tulip, gladiolus, and phlox. The beetles
usually feed upon the tender tissue between the veins of the leaves,
thereby skeletonizing patches of or the entire leaves, and leaving only
the ribs and veins. Blossoms and fruits also are consumed. Flowers,
shrubs, and, in cases of severe in festations, even large shade trees,
may be defoliated completely.
SKETCH SHOWING LIFE HISTORY AND FEEDING HABITS OF JAPANESE BEETLE
(Reproduced from U.S.D.A. Circular No. 332)
(click on image for an enlargement in a new window)
Several outbreaks of this pest now occur in National
Park and Monument areas in Region One. At George Washington Birthplace
National Monument, in Westmoreland County, Va., a heavy infestation has
become established National Capital Parks, Washington, D. C., have a
Japanese beetle problem. A vigorous attack was recently reported at Fort
McHenry National Park, Baltimore, Md. Morristown National Historical
Perk Morristown, N. J., is troubled with the pest, and the famous Statue
of Liberty National Monument on Bedloe's Island, N. Y., also is host to
the insect.
The Japanese beetle is now so widely and heavily
distributed that its complete eradication is beyond practical means of
accomplishment. Its spread may be checked and its numbers and the amount
of damage reduced, however, by energetic and intelligent application of
various control measures that are known at present. These measures are
briefly as follows:
1. Spraying the soil in infested areas with lead
arsenate to poison the grubs.
2. Spraying infested plants with a poison, such as
pyrethrum, which kills by contact with the insect.
3. Strict enforcement of state and Federal quarantine
regulations restricting the transportation of soil, potted plants,
nursery stock, and other plant material.
4. Trapping with specially designed beetle traps.
5. Hand collection before and during egg laying.
6. Introduction and encouragement of natural control
agencies, such as parasitic insect enemies, birds, and other animal
predators of both adults and larvae.
7. Planting species which are not susceptible to
attack.
8. In the yard and garden, valued plants may be
protected against damage by spraying them with a repellant such as
aluminum sulfate. Lead arsenate is a stomach poison as well as a
repellant but it destroys flowers, young leaves and other tender plant
tissues.
From all outward indications this foreign beetle is
here to stay; its ravages will vary in intensity from year to year
depending up on climatic and other factors; it will exact an annual toll
in destruction of vegetation; and our hope should be, through the
application and encouragement of natural and artificial controls,to keep
down the peak epidemics, thereby leveling off the curve of annual
losses.
REFERENCES
United States Department of Agriculture Circular No.
332, December, 1934, General Information about the Japanese Beetle in
the United States, by C. H. Hadley and I. M. Hawley.
United States Department of Agriculture Circular No.
237, Revised July, 1936, Control of the Japanese Beetle on Fruit and
Shade Trees, by W. E. Fleming and F. W. Metzger.
United States Department of Agriculture Circular No.
401, September 1936, Control of the Japanese Beetle and its Grub in Home
Yards, by W. E. Fleming and F. W. Metzger.
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