GALLS. 



LEPIDOPTERA; ToRTRicio/E: Eucosma. 

 GELECHIID/E: Gnorimoschema. 



DlPTERA; MYCETOPHILID/E: Sciara. 



ITONIDID^E, formerly called Cecidomyiidag : 

 Asteromyia, Caryomyia, Cecidomyia, Cincticornia, 

 Contarinia, Dasyneura, Hormomyia, Itonida, Lasi- 

 optera, Oligotroplms, Retinodiplosis, Rhabdophaga, 

 Rhopalomyia, Schizomyia, Thecodiplosis. 



TRYPETID/E: Eurosta,(Edaspis. 



AGROM YZID/E : A gromyza. 



HYMENOPTERA; SAW-FLIES: Euura, Pontania. 



CYNIPID.E: Acraspis, Amphibolips, Andricus, 

 Aulax, Biorhiza, Callirhytis, Cynips, Diastrophus, 

 Disholcaspis, Dryophanta, Gonaspis, Holcaspis, Neuro- 

 terus, Rhodites, Solenozopheria. 



If the galls are inhabited, a clue to the makers may be 

 gained by a study of the inhabitants. Mites have four 

 pairs of legs, at least when full grown; no wings; and are 

 very small. Aphids have three pairs of legs and they 

 sometimes have wings. Galls made by both of these 

 groups -are usually open. Saw-flies have thoracic, and 

 usually distinct abdominal, legs; their galls usually have a 

 large hollow on the inside. Gall-making Lepidopterous 

 larvae have thoracic but no abdominal legs. It is not so 

 easy to distinguish Hymenopterous and Dipterous larvae; 

 and it should always be remembered that galls may be 

 inhabited by creatures which did not make them para- 

 sites of the maker and also inquilines, "guests" which 

 avail themselves of the abundant food but do not directly 

 injure the maker of the gall. Some galls are complicated 

 communities. We speak of creatures "making" the galls; 

 the plants really do this, acting on some (not understood) 

 stimulus furnished by the animals. It is exceedingly 

 curious that insects which are so similar that they may be 

 distinguished only with difficulty cause such different and 

 distinctive galls. In addition to the unknown chemics 

 of the process, the gall-causing instinct is one of the most 

 mysterious things in entomology. 



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