310 OHIO EXPERIMENT STATION: BULLETIN 332 



PLANT LICE 



(Aphididae) 



While plant lice constitute one of the most important families 

 of destructive insects, from the standpoint of destructive shade and 

 forest tree pests, they rank quite low. With one or two exceptions, 

 therefore, they will be treated as a group. 



Description. — Plant lice are soft-bodied, winged or wingless 

 insects which for the most part are gregarious. The legs are long 

 and slender, as are usually the antennae, and the mouthparts are 

 fitted for piercing the food plant and sucking its juices. With most 

 species there are several generations annually, many of the females 

 having the power to bring forth living young without the interven- 

 tion of males. 



Natural enemies. — Plant lice because of their lack of natural 

 protecting armor and because of their sluggishness, fall an easy 

 prey to many parasites and depredators. Lady beetles, both in the 

 adult and larval stages; the larvae of Syrphus flies; the larvae of 

 lace wings (Chrysopidae) ; Hymenopterous parasites and fungous 

 diseases all contribute in holding the plant lice hordes in check. 



Control. — Frequently the dormant sprays applied for scale con- 

 trol are important checks against plant lice. During the summer 

 months, when plants become infested, a number of materials may 

 be employed, but one of the most universally satisfactory is nicotine 

 sulphate used at the rate of about 1 part to 500 or more parts of 

 water, with enough soap added to form a suds. This soapy, tobacco 

 spray should be applied in such a manner as to bathe the lice since 

 it is effective only when it comes in contact with the insect's body. 



THE PINE BARK APHID 



(Chermes pinicorticis Fitch) 



Description. — The pine bark aphid is a true plant louse, but the 

 insect itself is rarely seen, since usually it is hidden beneath a mass 

 of white, cottony secretion. These cottony masses occur in greatest 

 abundance on the trunk and larger branches of the host and when 

 numerous are very conspicuous. (See Plate LVIII, Fig. 1.) The 

 adult insects are dusky to reddish in color, some being winged and 

 some wingless. The eggs are oval, dusky-yellow and are secreted 

 in downy wax at the base of the needles. 



Life history and habits. — The first young appear in late April 

 or in early May and there are several generations during the season. 



