THE INSECT FAUNA OF THE GENUS CRATAEGUS 



1053 



live (fig. 103). The leaf does not become thickened in these galls. The 

 galls become extremely abundant on some trees, so that almost every leaf 



is deformed. The mites seem 

 rather than those in bright 

 sunlight. They become most 

 abundant during August, 

 when the galls are swarming 

 with the microscopic white 

 mites. The galls were found 

 most abundantly on Crata- 

 egus punctata, but they were 

 found also on C. pruinosa 

 and other native hawthorns. 



to prefer the shady branches of trees, 



FlG. 103. CROSS SECTION OF A CRATAEGUS 

 THROUGH THREE SERPENTINE GALLS 



LEAF, 





FlG. 104. HAWTHORN MARGINAL GALLS 



white mites which live within the pouches, 

 galls vary in size and shape, but are generally 

 about two millimeters high and are rounded on top 

 (figs. 106 and 107). They may be found at any 

 place on the leaf except on the larger veins. 

 They are fairly common on Crataegus punctata 

 but are not so abundant as the serpentine galls. 



Eriophyes sp. No. 2 (Hawthorn 



marginal gall) 



Galls very similar to those 

 of Eriophyes goniothorax Nal., 

 which are found on hawthorns 

 in Europe, are produced by 

 Eriophyes sp. No. 2. The 

 margin of the leaf is curled 

 tightly downward for a dis- 

 tance of two centimeters or 

 more (figs. 104 and 105), and 

 the curled margin is paler green 

 than the rest of the leaf. The 

 mites live within the curl. This 

 gall is not very common about 

 Ithaca, but was found in a few 

 cases on Crataegus cocdnea. 



Eriophyes sp. No. 3 (Thorn leaf 

 pouch gall) 



Many small, pale green 

 pouches, standing on the upper 

 side of the leaf and opening 

 beneath the leaf by a small slit, 

 are caused by microscopic 



The 



FlG. 105. 

 THROUGH 

 OF LEAF 



CROSS SECTION 

 CURLED EDGE 



