ORDER DIPTERA 249 



AGROMYZA 1 



This is the largest genus of leaf-mining Diptera. Its 

 members are all plant-feeders; most of them are leaf -miners 

 but some mine beneath the bark, a few produce galls and 

 some are stem borers. Agromyza pruinosa, A. aceriSj and 

 A. amelanchieris are cambium miners; A. tiliae, A. schineri, 

 and A. websteri, are gall-producing forms; A. aeneiventris, 

 A. simplex, and A. wrens, are stem-mining forms; the remain- 

 ing species of this genus, as far as their habits are known, 

 are leaf-miners. 



Our present knowledge of the biology of the North Ameri- 

 can species has been summarized by one of us, Frost (1923) 

 and his key for the determination of the known North Ameri- 

 can larvae is reproduced herewith: 



Key to the Leaf-Mining Laevae Agromyza 



1. Last abdominal segment with two fleshy lobes projecting from ventral 



posterior angle, resembling prolegs allecta 



Last abdominal segment without fleshy lobes 2 



2. Posterior stigmatal slits on curved horny projections at posterior end 



of body 3 



Posterior stigmatal slits at ends of short or long peduncles 4 



3. Ventral edge of second segment produced into two fleshy lobes 



angulata 

 Ventral edge of second segment not produced borealis 



4. Posterior spiracles with three stigmatal slits 5 



Posterior spiracles with more than three stigmatal slits 9 



5. Posterior spiracles fan-shaped, with stigmatal slits at end of separate 



lobes; mouth hooks triangular, with 4 teeth laterella 



Posterior spiracles with slits on stigmatal plates 6 



6. Posterior spiracles with stigmatal slits subparallel subnigripes 



Posterior spiracles with stigmatal slits arranged radiately 7 



7. Teeth of mouth hooks exceptionally long fragariae 



Teeth of mouth hooks normal 8 



8. Peduncle of the posterior spiracle long posticata 



Peduncle of the posterior spiracle short coronata 



9. Mouth hooks with four teeth melampyga 



Mouth hooks with two teeth pusilla and parvicornis 



1 This genus has been split by European workers into six genera: Domo- 

 myza, Ophiomyia, Melanagromyza, Haplomyza, Dizygomyza and Lirio- 

 myza. 



