INTRODUCTION 



The Syrphidae deserve to take high rank among the families of 

 insects because of their varied interest to the student of nature. It is one 

 of the largest and most beautiful of the families of Diptera and, so far as 

 adults are concerned, one of the best known S3'stematically. The larvae 

 present some very peculiar forms and a remarkable diversity of habits. 

 The famil}' po.ssesses some excellent examples of mimicr}-; perhaps no other 

 family of insects so much resembles another order as the S^'rphidae do 

 Hymenoptera. And, finally, the economic importance of its species, both 

 in the larval and adult stages, is, at the same time, ver^' great and ver}' 

 little appreciated. 



The economic status of the famih^ as a whole is decidedly beneficial 

 because of the aphidophagous habit of many of the larvae. There are no 

 well known pests; although one, whose larva feeds on the pollen and cells 

 of corn, has at times excited some alarm in certain localities; and the 

 larvae of certain species in Europe are known to destroy the bulbs of 

 such plants as Narcissus, Amaryllis and onion. None of the species has 

 ever .seriously or extensively intruded on the public welfare and con.se- 

 quently they are not well known to people generally. Their services 

 while exceedingly valuable have not been of such a conspicuous nature 

 as to change this condition. 



Although it has been well known for many years that the Syrphidae 

 are very beneficial because of the ravages of their larvae on plant lice, 

 it appears that our knowledge of their immature stages is deplorablj- 

 meagre. A small number of species has been more or less brieflj^ 

 described in one or more of their immature stages. Usually these are 

 isolated descriptions of single species, which entomologists have happened 

 u]ion wliile pursuing other lines of investigation. The various writers 

 have, of course, had no common basis of description, and most, if not all 

 of the descriptions are entirel}^ inadequate for specific separation. In 

 only one case did I find a figure of the larval mouth-parts; and I have 

 been able to find no detailed description of the posterior respiratory 

 apparatus in any paper. Again no one seems to have noticed the 

 remarkably constant occurrence of a definite number (12) of spines or 

 bristles (differentiated from any other vestiture which may be present) 

 in transverse rows across the body of the larva. 



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