412 Syrphidae. 



is not known: Trybom takes them to be an organ of locomotion, 

 perhaps also of respiration. For the rest something similar is found 

 in other Syrphid. larvæ, and the organ toay perhaps be homologous 

 with the organ in the Muscid larvæ described by Pantel (Bull. Soc. 

 Ent. de Fr. 1901, No. 4, 60, fig. 1—2). The larva is of a greyish or 

 yellowish white colour, and of a length of about 18 mm, the tail ex- 

 cluded. — The pupa is brownish, its upper anterior end forms a 

 flattened deciivity, at the hinder border of which the anterior spiracular 

 tubes prOtrude; these tubes are long, until 3 mm, a little curved, 

 directed upwards and forwards and a little diverging; on the lower 

 side they are beset with small tubercles (in other species as tenax 

 these tubercles lie on the sides and above, but not below); at the 

 front margin of the pupa the anterior larval spiracles are seen as two 

 short horns, the pupa has thus in all four horns, two long above and 

 two short below them. The larval tail is still found in the pupa, 

 curved in various ways, and on the ventral side the prolegs are visible. 

 The length is about 12 mm. 



No distinguishing characters are known for the larvæ of the various 

 species, but according to Miall such may be found in the small 

 spinules on the dermis, these being in some species simple in others 

 branched in various ways. 



The larvæ live in stagnant and putrid waters, ditches, in manure 

 and the like; they may be found together in very great numbers, I 

 once took them in a putrid ditch in which they were so numerous 

 that they were literally crowded. In the above mentioned cases of 

 their passing from the intestine of man they had probably been 

 swallowed with w^ater. The tail reaches the surface for respiration, 

 and as said it can be protruded to a great length. Reaumur ex- 

 perimented by filling water in a glass with larvæ, and he saw the 

 tail extended to about six inches, then it could not become longer. 

 With regard to the anterior spiracles Miall says that they are not in 

 function; this is, however, very improbable as it is then not under- 

 stood why they should be present; Trybom takes them to aet as 

 tracheal gills. For pupating the larva quits the water and pupates 

 in the vicinity, generally on the earth, but they are also sometimes 

 seen at the surface of the water. Sometimes they may be found 

 suspended by the tail; Zetterstedt (1. c. 662) mentions that he has 

 many times found pupæ of E. tenax hanging in this way, and F. Low 

 (Verh. zool. bot. Gesell. Wien, XVI, 1866, 949) mentions a pupa hanging 

 on a stalk ; Trybom mentions (1. c. 87) that he has taken many pupæ 

 of E. arhustorum suspended on a paling in a height of up to 2,5 meter 

 from the ground, the larvæ must thus have crept up to this height. 



