loo ' DIPTERA OF MINNESOTA. 



and to take the color of bees; the wings are at first short and tremulous, unfii 

 for flight; the limbs are weak; finally, desirous of flight, the insects start and 

 knock against the windows, pushing each other." 



Virgil's description of the process is very similar. The chamber 

 to be built must have four windows ; a young ox is to be slain and his 

 flesh pounded without shedding of blood ; thyme and cassia are to be 

 strewed. The words "trunca pedum primo" (with stumps of feet) 

 apply exactly to the larva of Eristalis. Wasps and hornets were simi- 

 larly supposed to proceed from the carcasses of horses. Osten Sacken 

 attributes this belief to the swarming of the bee-like bot-fly of the horse 

 (Gastrophihcs equi) about horses. The belief would be strengthened 

 by the occasional productions of the wasp-like Helophilus (a close 

 relative of Eristalis) from carcasses of the horse, though any other 

 dead body would do as well. 



Fig. 94. Wing of Syrphid, showing Fig. 95 and 96. Microdon tristis and pupal 



spurious vein, which characterizes this case. Original, 



family. After Comstock. 



And yet even these species, when adult, are frequently found upon 

 flowers. The maggots of one species live in the nests of bees and 

 wasps, possibly, it is thought, living upon the excrement of the larvae 

 of bees and wasps, and thus rendering the latter a service. The 

 maggots of the genus Merodon live in the bulbs of narcissus. The 

 larvae of the genus Microdon live in ants' nests. These maggots 

 (Microdon) are so unlike other dipterous larvae in their appearance 

 that when first discovered they were supposed to be little molluscs. 



We have illustrated freely in this interesting family, and reference 

 to Colored Plates I and IT, and to the various figures in the text will 

 give one a good idea of the appearance of these useful flies, useful in 

 that the larvae of very many of the species consume large numbers of 

 plant lice, one of the worst enemies of the agriculturist and gardener. 

 "The larvae are soft-bodied creatures, sometimes green or brown, 

 or variously marked, seen lying amongst a colony of aphids, or plant 

 lice, on rose bush, spirea, turnip, cabbage, or a host of other useful 

 and ornamental plants, and with the anterior part of their bodies so 



