142 
mate, and the clusters of bright yellowish-orange eggs (Fig. 34, 
a, a) are deposited on the under side of the leaves. Each cluster may 
contain from 25 to 75 eggs, or even more, and individual beetles 
have been known to lay as many as 3,000 eggs under certain arti- 
ficial conditions. The average number, however, is about 4.S0.* The 
fleshy, grub-like larvae (Fig. 34, b, h, h) hatch in four to seven days 
and at once begin to eat the potato leaves. They are dark red when 
hatched, but gradually become paler as they grow, with two rows of 
blackish spots along each side of the body. When two or three weeks 
old they go into the ground for pupation, emerging as beetles one 
or two weeks later. These beetles may feed and then go into hiber- 
nation, or eggs may be deposited for another generation. The num- 
ber of generations is still in dispute, but there is probably but one as 
a rule, only a few of the beetles first to emerge laying eggs for a 
second generation the same year. 
Natural Enemies. — Insect enemies of the potato-beetle are not 
uncommon, but it is doubtful if in Illinois they ever play any consid- 
erable role in reducing its numbers. Its commonest parasite in the 
vicinity of Chicago was a Tachina fly — PJiorocera rufilabris V. d. 
W.t The white eggs of this fly were common on the backs of both 
beetles and larvae — ;0n the thoracic plate of the adult, and between 
the thoracic segments of the larva. The maggots hatching from 
these eggs enter the bodies of the beetles or the larvae, soon killing 
them. Many predaceous enemies are known, including soldier-bugs, 
robber-flies, spiders, ground-beetles, ladybirds, tiger-beetles, rove- 
beetles, and some native birds and the domestic fowls. 
Methods of Control. — The two standard remedies for injuries by 
this pest are Paris green and arsenate of lead. In Illinois, dry Paris 
green, with or without lin'ie or flour, is used by nearly all potato 
growers. It has the advantage of being easy to prepare and apply, 
but there are offsetting disadvantages which make it less desirable 
than Paris green in water. It is less adhesive than the fluid spray, 
and hence must be applied more frequently, and more labor is re- 
quired. The dry poison is very injurious when breathed into the 
lungs by the person applying it. Bordeaux mixture should always 
be added to Paris green wdien it is applied in water — as also to the 
arsenate of lead — for this compound spray is more efi^ecti\e against 
flea-beetles, and is a remedy for blight. Furthermore, the lime in 
the Bordeaux unites with the Paris green, thus increasing its adhe- 
siveness, and it changes the soluble arsenic to insoluble, thus pre- 
venting the burning of the foliage which often follows when Paris 
green is used alone. The method of preparation is 'given on pages 
^Further Biological Notes on the Colorado Potato-beetle. LeptUwtarsa 
decetnlineata (Say), by Alec. Arsene Girault. Annals Ent. Soc. America, 
Vol. I, No. 2 (June, 1908), p. 158. Columbus, Ohio. 
tDetermined by C. A. Hart. 
