FAMILY SYRPHID.i: THE FLOWER FLIES 249 



The larvfe are variable in habits and form. Some live in the nests 

 of ants, termites, bees, etc., but nothing is known regarding their rela- 

 tionship to their hosts. JMost of them live in decaying vegetation, while 

 a very few are injurious to growing plants and bulbs. Among the 

 well-known larval forms are the rat-tailed maggots which may be found 

 in licjuid media containing decaying vegetation and very rarely in 

 carrion. The larva? may be divided into four types : the Microdon type, 

 with an unusually hard, convex upper surface and flat, soft ventral 

 surface; the Syrphus type, some of which approach the first group in 

 ap])earance, living upon aphids, decaying vegetation and plants; the 

 short-tailed maggots, living in decaying vegetation; and the rat-tailed 

 maggots which live in liquid media. 



In the key to tlie genera several minute characters are used. These 

 may prove difficult at first but once the student is familiar with them 

 they will be found to l)e most useful. In some cases there may be 

 difficulty in deciding the genus to which a species belongs but com- 

 parison with specimens of known genera will aid in reaching a decision. 

 The final recourse, after careful study, is to send the puzzle to a spe- 

 cialist and receive his opinion. IMost of them will gladly tell you what it 

 is and return the specimen. 



KEY TO GENERA 



1. Antennse with a terminal style, the third antennal segment tapering.. 2 

 Antennse with a dorsal arista, if sub-apical the third segment is not 



tapering from the base 3 



2. Eyes bare (24, 46. 51 ) * Cerioides Rondani 



Eyes pilose Callicera Panzer 



3. Arista bare; antennae usually longer than the convex, pilose face; third 



vein usually with a stump of vein extending into the apical cell; 

 anterior crossvein situated before the middle of the discal cell; 



apical crossvein often recurrent 4 



Arista variable; antennae usually shorter, if elongate the humeri are 

 bare, or the arista plumose; face concave, tuberculate or carinate, 

 never rather evenly convex 6 



4. Third vein with a stump of vein extending into the apical cell 5 



Third vein without such stump but there may be one from the fourth 



vein and from the apical crossvein Mixogaster Macquart 



5. Abdomen spatulate Rhopalosyrphus Arribalzaga 



Abdomen not spatulate (1, 53, 59) t Microdon Meigen 



6. Humeri pilose 7 



Humeri bare, often mostly concealed by the occiput 18 



Curran, 1925, Kans. Univ. Soi. Bull., xv. p. 25. 

 Curran, 1925, Kans. Univ. Sci. Bull., xv, p. 48. 



