Editors: W.T. Wilsey, C.R. Weeden, and A.M. Shelton
Bean Beetle (Epilachna varivestis)
- Life Cycle
for larger image
The adult Mexican bean beetle is about 1/4 inch (6 mm) long, very
convex and short in form. It varies in color from yellow when newly
emerged from the pupal stage to a coppery-brown when mature or in
the overwintering stage. Each wing cover had eight black dots in three
rows across the back when the wings are at rest. When disturbed, the
adults fall from the plant and exude a yellow liquid from their leg
joints. The adult beetles pass the winter under trash and other ground
cover along hedgerows and in similar protected places.
After feeding 1-2 weeks on the preferred host crop of beans, the adults
deposit eggs on the underside of the leaves. The eggs are about 1/20
inch (1.2 mm) long, orange-yellow in color and fastened on end in
close groups of 40-50 or more. The eggs hatch in 5-14 days depending
The nymphs are yellow in color and the body is covered with six rows
of long, black-tipped spines. The larval stage lasts for 2-5 weeks:
when full grown the larvae or grubs are 1/3 inch (8 mm) long. Pupation
takes place on the bean leaves.
The pupa is orange in color and is attached to the leaf by the old
larval skin. The adult emerges in approximately 10 days. The total
period of development from egg to adult averages 33 days under midsummer
Damage inflicted by Mexican bean
beetle on beans
Some information on this page
taken from Insects of Beans: Cornell Coopertive Extension factsheet number
139VCFS770.00 authored by A. A. Muka.
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Copyright is held by Cornell University.
Maintained by Jason D. Plate. Last updated Mar. 8th, 2007.