256 MAINE AGRICULTURAL, EXPERIMENT STATION. 1916. 

 ARTIFICIAL KEYS TO THE KNOWN LARVAE AND PUPAE OF SYRPHIDAE 



KEY TO TYPES OF LARVAE 



1. Body terminating in a long, flexible and extensile, rat-tail-like 



respiratory appendage (often longer than the body). Larvae 

 aquatic, semi-aquatic, or living in moist decaying materials. 

 The puparium with a pair of prominent, anterior, respiratory 



cornua ( See also p. 210) 



iv. THE LONG-TAILED FILTH-INHABITING TYPE (Genera Eristalis, 

 Helophilus, Chilosia, Chalcomyia, Sericomyia, Mallota, etc.) 

 Posterior respiratory appendage considerably shorter than one- 

 fourth the length of the body, rigid. Habits various, but not 

 aquatic larvae 2 



2. Larvae short-oval or rounded in outline, convex above, and with 



a very flat, creeping-sole, ventrally, around which is a fringe 

 of spines. The shape constant and sub-hemispherical; no 

 evident transverse wrinkling of the body-wall, but the dorsum 

 often nicely reticulated. Larvae living in ant-nests. The pu- 

 parium sub-hemispherical, and with prominent anterior cor- 

 nua. ( See also p. 211) 



v. THE MICRODON TYPE (Genus Microdon) 



Shape of larva elongate-oval with the venter flattened, or sub- 

 cylindrical; the outline not constant, but the body especially 

 the anterior end, capable of considerable extension when 

 active 3 



3. Body nearly cylindrical, the anterior end not attenuated, but 



rounded out, forming a false-head. Three fleshy, finger-like 

 processes at each side of the last body-segment. No external 

 mouth-parts. Puparium with prominent anterior cornua. (See 

 also p. 210) 



III. THE SHORT-TAILED FILTH-INHABITING TYPE (See key below) 



The anterior end of the body considerably attenuated, when active ; 

 no false-head. Black, chitinized mouth-parts present 4 



4. Body nearly circular in cross-section. Mouth-parts of two re- 



curved hooks, uniting basally into a mouth-hood. Stigmal 

 j plates with groups of minute, palmately-arranged, plumose 



hairs. ( See also p. 209) 



ii. THE BORING TYPE (Merodon equestris Fabr.) 



Body always noticeably, often much, flattened. Mouth-parts of 

 two, A-shaped jaws. Stigmal plates with various ornamentation 

 but not with plumose hairs. Puparium rounded in front, at- 

 tenuated behind, and apparently without pupal respiratory cor- 

 nua (See also p. 208) 



i. THE APHIDOPHAGOUS TYPE (See key below) 



