No. 494] FASCIATIONS OF KNOWN CAUSATION 89 



production of a gall. Among the Araclmida, many of the 

 mites do so, some species causing serious injuries; for 

 instance, the pear leaf blister mite, Eriophi/es pyri, and K. 

 oleivorus, which causes the so-called "russet" oranges. 40 



To the Hemiptera, of which the plant-lice, Aphidida?, 

 are best known, belongs the dreaded Phylloxera vastatrix, 

 which some thirty years ago so seriously crippled the 

 vineyards of France. It forms galls on both the leaves 

 and the roots. The Diptera, to one of the families of 

 which our common house fly belongs, yield the Cecido- 

 myidae. One of these very small insects is the cause of 

 the goldenrod rose. Neither the Lepidoptera nor the 

 Coleoptera have many members which are the cause of 

 gall formation. This is different as far as the Hymen- 

 optera are concerned. A large number of species, espe- 

 cially those belonging to the Cynipidae, are the cause of 

 the formation of some of the largest, most strikingly 

 colored galls, of which those occurring on oaks (Cynips) 

 and roses (Bhodites) are probably the most familiar. 



In some cases the causation of fasciations has been as- 

 cribed to gall-forming animals. Kerner 41 speaks of the 

 fasciations of the ash, Fraxiu.us excelsior and F. ornus, 

 caused by a mite, Phytoptus (Eriophyes). De Vries 42 

 mentions a stem of Eieracium nil gat urn attacked by Au- 

 lax Hieracii which was normal below the gall, but above it 

 was fasciated. Not only fasciations, but numerous other 

 monstrosities have been brought into relation with gall 

 insects. Treub 43 observed virescence caused by the same 

 insect. Nalepa 44 mentions Phytoptus anthocoptes as 

 the cause of virescence of flowers, thickening of the capita 

 and frequent secondary formation of capitula on Cirsium 



40 Cook, M. T. Insect galls of Indiana. Indiana Dep. of Geol. and Nat. 

 Kes., 29th Annual Eeport, 801, 1904. 

 "Ibid., 2: 549. 



"Treub, M. Notice sur l ai^rrtt. < .nnposees a propos d'une mon- 

 struosite de VHieracium nmbellatum. Arch. Neerl. d. sc. phys. et nat., 8: L 



"Nalepa, A. Neue Arten der Gattung Phytoptus und Cecidophyes. 

 Dcnlcschr. d. 1c. Acad. d. Wiss., 59: 525, 1892. 



