220 mains; agricultural experiment station. 19 1 6. 



Practical Measures. 



Since the above analysis shows that the economic importance 

 of the Syrphidse is overwhelmingly beneficial, one is naturally 

 desirous of knowing what could be done to favor, or foster them 

 and increase their numbers. 



1. The first thing to be done it seems to me is to educate 

 people and especially agriculturists to discriminate between these 

 Flower-flies and stinging Hymenoptera. The writer, knows 

 from personal observation that many of these beneficial insects 

 are constantly being killed as "sweat-bees" under the impression 

 that they can sting. Whereas, they are absolutely unable to 

 harm the person in any way; and furthermore, are, both as 

 larva and adults, (with the exception of a very few species) 

 among the farmer's most valuable animal friends. 



There are several simple ways in which these two groups can 

 easily be distinguished in spite of the great resemblance in color, 

 form and habit. // the insect is flying, the Flower-fly can be 

 recognized by its distinct manner of flight, which has given the 

 group the name of "Hover-flies." They constantly poise in the 

 sunlight, or about flowers, remaining suspended in one place 

 for a considerable time without any apparent movement of the 

 body, the wings beating so rapidly as to be practically invisible ; 

 then dart away and quickly return, the body always in a tense 

 horizontal position. Bees, when flying, habitually weave back 

 and forth or bob up and down. On closer inspection most of 

 the species can be distinguished by the shorter antennae 

 ("feelers") which are not easily seen in flight; while the antennas 

 of the bee are usually visible in front of the head. // the insect 

 comes to rest, the Flower-fly is apt to keep its wings partly 

 spread, the bee or wasp to fold them closely or cross them at 

 the tips. // you have the insect in your hand, see if the wings 

 on one side can be separated into two readily. The bees have 

 two pairs of wings hooked together, but easily separable ; the 

 Flower-flies of course have only one wing on a side. Back of 

 the base of the wing in the Flower-flies is a small knobbed thread 

 (Fig. 29-4) visible to the naked eye on very careful examina- 

 tion, wanting in the Hymenoptera. And, finally, if a hand lens 

 is available look for the false vein (Fig. 34-7) on the wing, 

 which is the most distinctive characteristic of the Syrphidse. 



