6 BULLETIN 1223, U. S. DEPARTMENT OF AGRICULTURE, 
Trees which have been attacked for a number of years by this 
insect, 1f they do not die, finally seem to develop a certain amount 
of resistance to its injury. The history of this scale insect through- 
out North America has been much the same. It causes much con-— 
cern to the owners of shade trees for a number of years after mak- 
ing its first appearance, and then seems slowly to lose its grip upon 
the trees until 1t causes a much smaller amount of damage. This— 
is especially true in sections of the Eastern States and Canada, 
where less attention than formerly is now paid to this once dreaded 
insect. 
FOOD PLANTS. 
The recorded food plants of the European elm scale in the United. 
States are English elm (Ulmus campestris), Scotch or Wych elm — 
(U. scabra), European species, and white or American elm 
(U. americana), cork elm (U. racemosa), and slippery elm (U. 
fulva), American species, and their varieties. Probably all species 
of elms are subject to attack by this insect, although some have not — 
yet been recorded as host to it.* } 
Tn 1895 Lintner, then State entomologist of New York, collected 
immature specimens of a scale insect on willow at Loudonville, 
N. Y., which were determined at that time as the Kuropean elm 
scale. This determination has since been corrected and those speci- 
mens have now been identified as a species of Eriococcus. 
Signoret (79, p. 21), a French entomologist, has stated that he 
collected Gossyparia spuria on alder in France. Lindinger (72, p. 
54, G4, 122, 159, 338), also a European entomologist, gives the fol- 
lowing hosts in addition to elm: Acer sp., Alnus sp. (very prob- 
bly Signoret’s record), Corylus avellana, Frarinus excelsior, and 
Viscum album, all European records. From the fact that the Kuro- 
pean elm scale has not been found on any of these hosts in America, 
the writer is inclined to believe that some related species has been 
confused with it. At any rate there are no records of the European 
elm scale occurring on anything except elms in America. The 
writer has seen both alders and willows growing with their branches 
interlaced with those of infested elms, yet not a scale could be 
found on either of them. One specimen of Zelkova acuminata, 
which belongs to the elm family (Ulmaceae), has been seen growing 
near a large number of infested elms, but no infestation was 
apparent upon it. 
DESCRIPTIONS. 
EGG “(PI I, “A); 
Oval in outline, twice as long as wide, 0.36 by 0.19 millimeter. Color bright 
yellow; surface smooth and shiny. Eyes of larva visible as two black spots 
through the egg membrane. 
4 Aside from the European elm scale the principal insect pests of the elm in the West 
are the carpenter worm, Prionorystus robiniae Peck, which bores into the trunks and 
main limbs, often killing large branches and occasionally whole trees; an aphid, Myzo- 
callis ulmifolii Monell, and a leafhopper, Empoa ulmi L., both of which suck the plant 
juice from the elm leaves and produce an abundance of honeydew. They are sometimes 
worse than the elm scale in this respect. ; 
The elm leaf-beetle, Galerucella luteola Miill., is probably the worst enemy of the elm 
in the East. where it defoliates a great number of trees every year. It has also been 
introduced into the West, having been reported several years ago from Portland, Oreg. 
This has not yet become a serious pest in the West, but may in the near future. 
