580 Syrphidae. 



time they were treated as such. In 1839 Schlotthauber (Isis 1840, 922) 

 mentions for the first time the larva as belonging to Microdon and 

 clears up the earlier mistakes. Zetterstedt mentions in 1843 (Dipt. 

 Scand. II, 640, 641) the pupa of M. devius (apiformis), found under 

 the bark of a tree, and another attached to a stalk of grass. In 1845 

 Elditt describes (as M. miitahilis) the pupa of a species which seems 

 to be Eggeri (Stett. ent. Zeitg. VI, 1845, 384, Tab. I, Fig. 6-14). In 

 1848 Wissmann describes (Stett. ent. Zeitg. IX, 1848, 79) the larva of 

 M. miitahilis (as apiformis M.). Laboulbéne mentions briefly an un- 

 determined Microdon larva (Ann. Soc. Ent. de Fr. 6, II, 1882, BuU. 

 XGVI et GVI). In 1883 Poujade describes (Ann. Soc. Ent. de Fr. 6, 

 III, 1883, 23, PI. I, fig. 1—16 et Bull. XCIX) the metamorphosis of 

 M. -Eggeri (as mutabilis). Besides other papers, among which are 

 especially an interesting one by Wheeler (Journ. New York Ent. Soc. XVI, 

 1908, 202) treating North American species, and one by Donisthorpe 

 about M. mutabilis (Ent. Record 18, 1909), there appeared in 1912 an 

 elaborate monograph over the developm ental stages of Microdon by 

 Maria Andries (Zeitschr. f. wiss. Zool. 103, 300, Tab. III— V), in which 

 the stages of M. mutabilis, of a new species, rhenantis and of Eggeri 

 with a new var. major are described and figured; the work contains 

 a somewliat complete bibliography. The author declares all the earlier 

 descriptions which she knew, except the one by Wissmann, to belong 

 to Eggeri, or perhaps also to the otherwise unknown M. devius and 

 latifrons ; as remarked above Zetterstedt has, however, briefly described 

 the pupa of devius, which seems more similar to mutabilis than to 

 Eggeri. 



According to the descriptions the larva is short oval in circum- 

 ference, flat below, very arched above; along the margin all round 

 is a fringe of short filaments; at the anterior end the margin is a 

 little incised for the head, and there are here the usual, antenna-like 

 organs, the last joint of which bears two relatively long, styliform 

 papillæ. Above at the posterior end is a short posterior spiracular 

 process, a little divided at the end and here bearing the spiracles. 

 No segmentation is visible (but Andries gives, however, after studying 

 the youngest stage, the number as twelve). The larva of Eggeri (to 

 which, as said, according lo Andries all the earlier descriptions, except 

 the one by Wissmann, probably belong) is curiously reticulated above, 

 as it has a network of raised polygonal meshes, beset with special hairs; 

 from the head-end to the posterior spiracles run two longitudinal lines 

 without reticulation ; the larva is brown, of a length of 8— lOmm; 

 the larva of mutabilis (and rhenamis) is only somewhat reticulated 

 along the margin, but is for the rest rather smooth; it is of whitish 



