SYRPHIDAE 0E MAINS. 221 



2. Not only should the adults be spared but the larvae 

 (Figs. 29-1; 30-d; 34-i") on plants, among aphids, should be 

 given careful protection. Too often they are killed under the 

 supposition that they are damaging the plant. The figures and 

 descriptions should enable one to distinguish these larvae ; but, 

 if there is any doubt, careful observation will usually be 

 rewarded by seeing one of them attack and devour an aphid. 



3. The writer, with the assistance of Mrs. Cleo Fouch 

 Metcalf, is investigating the effect of contact insecticides, such 

 as are used for plant-lice, on these predaceous larvae, in the 

 hope that an effective spray for the aphids may be found which 

 will not destroy the larvae. In this way the latter might be left 

 on the plants to seek out and destroy any aphids which escaped 

 the spray, and thus tend to make the control measures perfect. 

 The investigation has not gone far enough to justify conclu- 

 sions, but it may be said that in laboratory tests a solution of 

 Black Leaf 40*, 1 to 1000 of water with soap added, killed every 

 aphid and only a small percentage of the larvae. The effect of 

 this insecticide on the larvae under field conditions will be fur- 

 ther observed. 



4. During late summer and autumn, especially, a large per- 

 centage of the puparia of Flower-flies are parasitized by- a small 

 wasp which kills them. Such puparia can be easily told, after 

 a little experience, by the fact that they do not completely 

 inflate dorsally and soon become darker in color than normal. 

 Much good could be done by careful observers in destroying 

 such parasitized puparia wherever found. 



Species Reared in the State. 



During the summer of 1915 at this Station, I succeeded in 

 rearing from eggs or larvae twenty species of Syrphidae, nine of 

 which have apparently not previously been described in the 

 immature stages. These species fall into three of the structural 

 types of larvae already described, as follows : 



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