THE INSECT FAUNA OF THE GENUS CRATAEGUS 1085 



pomi De Geer, Aphis (Green apple aphis) 



During June and July the succulent sprouts of European and native 

 hawthorns are badly infested by green apple aphids. Whenever the weather 

 becomes unfavorable for their enemies they increase rapidly and infest 

 entire trees or hedges, but fair weather checks them again. 



prunifoliae Fitch, Rhopalosiphum (Apple bud aphis) 



The dark green stem mothers of the species Rhopalosiphum prunifoliae 

 begin to appear on the buds of native hawthorns as soon as the bud scales 

 have separated enough to show the green leaves within. The colonies 

 increase during April and early May, doing some damage to the young 

 leaves and buds, but before June they migrate from the trees to grasses 

 and are not often found on the trees between early June and late autumn. 

 The winter eggs are laid on hawthorn twigs and buds. 



Coccidae 



corni Bouche, Lecanium (European fruit lecanium) 



The species Lecanium corni is often very abundant on the lower side of 

 branches of native hawthorns, and occasionally a branch is found to be 

 almost entirely covered with these scales. Lower or inner branches that 

 receive a scanty supply of light appear to be killed by them. The young, 

 flat scales are sometimes very plentiful on the leaves in late summer. 



furfura Fitch, Chionaspis (Scurfy scale) 



The flat, whitish scale known as Chionaspis furfura is very common and 

 noticeable on the bark of all Crataegus species which the writer has 

 observed. The small, elongate, white, male scales are often very abundant 

 on the leaves and bark of Crataegus punctata. The injury caused by 

 these scales is not noticeable. 



perniciosus Comst., Aspidiotus (San Jose scale) 



Although the San Jose scale is fairly common on all species at Ithaca, 

 it does not seem to increase rapidly enough to become injurious. It is 

 more commonly found on the smooth bark of young trees than on old, 

 rough-barked trees. 



ulmi Linn., Lepidosaphes (Oyster-shell scale) 



The oyster-shell scale is common on the bark of native and European 

 hawthorns, and a few badly infested branches have been found. Gen- 

 erally, however, this species seems to be unimportant as a pest of Crataegus. 



vitis Linn., Pulvinaria (Cottony scale) 



The species Pulvinaria vitis is occasionally found on the twigs and 

 branches of native hawthorns, but is not very abundant. 



