26 CIRCULAR 639, U. S. DEPARTMENT- OF AGRICULTURE 
occasionally happens that larvae, which feed on the roots, are carried 
on the plants from the beds to the fields. 
Flea beetles begin to infest tobacco fields very soon after the plants 
are set out. At first they are most numerous at the edges of the 
fields, but they gradually make their way toward the middle areas. 
After they have become well established on tobacco there appears 
to be no marked tendency for further movement unless they are 
disturbed. 
The egg-laying period is apparently of rather short duration at this 
season of the year, as the beetles usually begin to die off from natural 
causes during the first part of April. 
There is an intervening period of from 2 to 3 weeks when very 
few beetles are usually seen in the fields. Then the adult progeny 
of the overwintered flea beetles usually appear in this region about 
= 
FicurE 29.—Woodland adjoining a tobacco shade field. Flea beetle adults 
hibernate along the edges of such wooded areas. 
the second week in May. The majority of them may appear at 
about the same time or they may continue to emerge over a con- 
siderable period. Large numbers often emerge after showers which 
soften the upper soil sufficiently to allow free access to the surface. 
After a feeding period of about 3 weeks these beetles begin to 
lay eggs. The incubation of these eggs and subsequent development 
of the larvae are similar to those of the first generation, but may 
be accomplished in a much shorter time. Adults of the second 
generation usually appear about the time tobacco has reached ma- 
turity, and frequently cause much damage. 
From this it is seen that the tobacco crop is attacked by the over- 
wintered brood and by two later broods of flea beetles. If favored 
by natural conditions, each generation brings about an enormous 
increase in the number of individuals. 
