in more aquatic, filthy environments (fig. 14:53?'). The 

 Syrphidae with strictly aquatic larvae belong to the 

 long-tailed type comprising the subfamilies Seri- 

 comyiinae and Eristalinae. A few Cheilosiinae with 

 short-tailed larvae have aquatic habits, but the 

 majority of this subfamily, together with tho Xylotinae 

 and Volucellinae, prefer drier environments under 

 bark, in decaying wood and plant material, in tree 

 holes, or in refuse. Metcalf (1913, 1916) and Heiss 

 (1938) have published excellent general discussions 

 of syrphid biologies with emphasis on the nonaquatic 

 species, and Johannsen (1935) has constructed a key 

 and given descriptions of the known aquatic larvae. 

 The following keys are only to the genera known to 

 be aquatic. 



Keys to the North American Genera of Aquatic Syrphidae 

 Adults 



1. Posterior femora lacking a patch of black setulae on 

 their anterior bases; 3rd vein at most moderately 

 curved into apical cell 2 



— All femora with such setulae; 3rd vein strongly curved 

 into apical cell (fig. 14:53A) (ERISTALINAE) 4 



2. Anterior cross vein situated well before middle of 

 discal cell, or the mesonotum with bristles; arista 

 bare or slightly pubescent (CHEILOSIINAE) 3 



— Anterior cross vein situated at or beyond the middle of 

 discal cell; thorax rarely with short spines; arista 

 plumose (SERICOMYIINAE) Sericomyia Meigen 



3. Face and frons rugose; disc of abdomen opaque black, 

 the sides shining Chrysogaster Meigen 



— Face and frons smooth; disc of abdomen either wholly 

 shining or with shining spots or bands 



Myiolepta Newman 



4. Marginal cell closed and petiolate (fig. 14:53/») 



Tubifera Meigen 



— Marginal cell open 5 



5. Large, robust species; thorax thickly yellow or orange 

 pilose; hind femur swollen and arcuate . Mallota Meigen 



— Smaller and more slender species; hind femur not 

 swollen and arcuate Helophilus Meigen 



461 

 Wirth and Stone: Diptera 



Williston in water near the shore of a pond in Now 

 York. The following key is adapted from Shannon 

 (1916). 



Key to Adults of the California Species of Chrysogaster 



1 . Lower posterior edge of scutellum with a single row 



of downward projecting pile; Humboldt County 



chilosioides (Shannon) 1922 



— Lower posterior edge of scutellum without downward 

 projecting pile 2 



2. At least the first 2 tarsal segments yellow or yellowish 

 red; antennae elongate; mesonotum with coppery vittae; 

 central and southern California. . .bellula Williston 1882 



— Legs entirely dark 3 



3. Third antennal segment approximately 3 times as long 

 as broad 4 



— Third antennal segment less elongate 5 



4. Pile on frons and ocellar triangle black; San Francisco 

 and Marin counties nigrovittata (Loew) 1876 



— Pile on frons and ocellar triangle whitish; Alameda and 

 Sonoma counties (6*) stigmata Williston 1882 



5. Squamae and halteres darkened 6 



— Squamae and halteres whitish 7 



6. Dark, greenish black species; pile on ocellar triangle 

 and frons rather long and black; California 



pacifica Shannon 19 16 



— Dark, steel-blue species with very short whitish pile 

 on frons and ocellar triangle; Reno, Nevada 



unicoloT Shannon 1916 



7. The transverse pollinose band below antenna reduced 

 almost to 2 spots at the eye margins; frons black; arista 

 a little shorter than the antennae; Alameda and Sonoma 

 counties (?) stigmata Williston 1882 



— The pollinose facial band complete and distinct; frons 

 greenish metallic 8 



8. The vittae on the mesonotum very faint, paler than 

 the rest of dorsum; arista a little longer than the 

 antenna; rather large, robust species; Monterey County 

 robusta Shannon 1916 



— The vittae on mesonotum coppery colored; arista a 

 little shorter than antenna; small species; Lake Tahoe; 

 Mono County parva Shannon 19 16 



Larvae and Puparia 



1. Respiratory tube shorter than body when extended (fig. 

 14:53c); last 1-3 abdominal segments each with a 

 ciliate,- pointed lobe on each side.. Myiolepta Newman 



Chrysogaster Meigen 



— Caudal respiratory organ when extended, much longer 

 than the body (fig. 14:53;') {Sericomyia also keys out 

 here) 2 



2. The 2 longitudinal tracheal trunks of larva undulating 

 (fig. 14:536) Helophilus Meigen 



— Tracheal trunks of larva straight (fig. 14:53a) 3 



3. Larva distinctly flattened posteriorly with distinct 

 papillae bearing coarse hairs Mallota Meigen 



— Larva not flattened, without papillae bearing hairs 

 Tubifefa Meigen 



California Species of Aquatic Syrphidae 



Subfamily CHEILOSIINAE 



Genus Chrysogaster Meigen 



Johannsen (1935) found puparia of C. pulchella 



Genus Myiolepta Newman 



Greene (1923) described the puparium (fig. 14:53c) of 

 M. nigra Loew which he found in a hole in a tulip 

 tree. Immature stages of several European species 

 have been described from decaying wood of hollow 

 poplars. 



calif ornica Shannon 1923. 

 lunulata Bigot 1884 



(= varipes auct. non Loew). 



Mendocino County 

 Sierra Nevada 



Subfamily SERICOMYIINAE 



Genus Sericomyia Meigen 



Bloomfield (1897) recorded the immature stages of the 

 European S. borealis Fallen from a pool in a peat bog. 

 Curran (1934) keys twelve North American species, 

 none of which have been recorded from California. 



