12 BULLETIN 1223, IT. S. DEPARTMENT OF AGRICULTURE. 



of the elm are more evident than those of the scale insect, it is well 

 to indicate this relationship, especially since the time of application 

 of control measures often depends upon both. The tree and the 

 insect awaken from hibernation at the same time. The females 

 undergo their last molt while the fruit is forming on the tree. Most 

 of them have attained a large size and are secreting their semi- 

 cocoons when the fruit begins to fall from the tree. The semi- 

 cocoons are completed by the time most of the leaves are full grown, 

 and egg- laying starts two or three weeks later. The second-stage 

 larvae migrate from the leaves back to the twigs and branches when 

 the tree sap becomes sluggish and the leaves begin to yellow and fall, 



NATURAL ENEMIES. 



The insect enemies of the European elm scale are very scarce and 

 play but a small part in its control. The first and only record of 

 the rearing of a parasite from this scale in the United States was 

 in 1898 by R. A. Cooley (1), who reared half a dozen specimens at 

 Concord, Mass. These have never, been described, but remain under 

 the manuscript name of C occo phagus gossypariae Howard. The 

 writer endeavored a number of times to obtain parasites from west- 

 ern material, but was unsuccessful. Either there are none in the 

 West or they are so scarce that they do not figure in the control of 

 this scale insect. 



The predatory enemies of the European elm scale are somewhat 

 more numerous, but even they can not be considered as important 

 agencies in its control. The twice-stabbed lady-beetle, Ghllocorus 

 bivulnerus Mulsant, is the most common enemy of the European- 

 elm scale. Essig (6, p. 119-120) mentions that Dr. A. J. Cook 

 reported this beetle as preying upon the scale insect at San Rafael, 

 Calif. The writer also has observed beetles of this species feeding 

 upon the body contents of adult females. 



Both larvae and beetles of the black lady-beetle, Rhizobius ven- 

 tralis Erichson, fed upon this scale insect when in captivity, and in 

 all probability feed upon it when free, as it is usually found abundant 

 upon scale-infested trees. The common black-spotted red lady- 

 beetle, Hlppodamia convergens Guerin, and . its variety, ambigua 

 LeConte, have been found rather plentiful upon infested trees and 

 probably prey upon this scale insect, yet none have been observed 

 actually feeding upon it. 



The green lacewing Chrysopa calif ornica Coquillett has also been 

 reared upon the European elm scale and is found to some extent upon 

 infested elms. No other insect enemies of this pest have been 

 observed. 



