ORDER DIPTERA 261 



surface of the leaves in which they are feeding. As a result 

 the leaves dry up. 



The larvae of this species pupate in the mines, usually in 

 the leaf sheath. The adult, upon emerging from the pupar- 

 ium, tears open the dry tissue at or near the pupal case and 

 makes its escape. 



PHYTOMYZA* 



This is in number of species the second largest genus of 

 leaf-mining species among the Diptera. The larvae of 

 this genus, are largely leaf-miners. It is the only genus 

 among the Diptera that forms a natural group with such a 

 habit. The food plants of most of the species are already 

 known. The smooth larvae make mostly linear or serpentine 

 mines on a variety of plants; and the plants mined may 

 differ in their leaves as greatly as do Impatiens and thick- 

 leaved hollys. The white tracery of the columbine miner, 

 P. aquilegiae, on leaves of Aquilegia is familiar to everyone. 



Key to the Larvae of Phytomyza 



1. Anterior spiracles distinctly bifurcated nigritella 



Anterior spiracles fan-shaped or semicircular, but not bifurcated 2 



2. Mouth hooks with 2 or 3 teeth... 3 



Mouth hooks with 4 teeth 7 



3. Mouth hooks with 2 teeth 4 



Mouth hooks with 3 teeth 6 



4. A tentacle on dorsum of first segment aquifolii 



No tentacle on first segment 5 



5. Posterior spiracles semicircular, with 22 stigmatal slits plumiseta 



Posterior spiracles semicircular, with 8 or 9 stigmatal slits, .plantaginis 



6. Posterior spiracle with 15 to 18 stigmatal slits albiceps 



Posterior spiracle with 9 stigmatal slits, peduncle of medium length 



chrysanthemi 



7. Anterior spiracles with 9 stigmatal slits ilicis 



Anterior spiracles with 26 stigmatal slits nigritella 



* The identity of some of these species especially P. aquilegiae Hardy, 

 P. ilicis Curtis, and P. aquifolii are in dispute. No attempt is made to 

 straighten synonymy here. 



