Beneficial Insects. 



329 



Among other destroyers of aphides, some species of Syrphits^ 

 a genus of the SyrphidcE, rank next in usefuhiess to the Cocci- 

 nellae^ especially the species known as Syrphus rihesii, Syrphus 

 balteatus, and Syrphus vitripemiis. There are several other 

 species of this genus of this large family of dipterous insects 

 which feed upon aphides, especially one defined as Catabomba 

 pymst7'i ; but the three mentioned are the most common. It 

 is the larvae alone of these insects that feed upon aphides. 

 The Syrphus flies do not eat them, but are seen in summer 

 weather flying round flowers and blossoms, from which they 

 appear to obtain food in the shape of honey or pollen. Meigen 

 says that they may be seen flying very rapidly, and occasion- 

 ally resting, or hovering in the air for a brief space, from 

 early spring to late autumn. Meigen also remarks 

 that their flight is quick, and is taken by fits and starts. 

 Curtis^remarks, "These flies are so numerous as to be in a great 

 measure the cause, I believe, of the incessant vibration of the air 

 or buzzing, which we have in the country on fine, still, sunny 

 days in the summer and autumn months." They somewhat 

 resemble small wasps, so that, as Westwood suggests, they 

 are constantly mistaken for them by the inexperienced, 

 They are found in large swarms towards the end of the 

 summer, especially the species known as Syrphus rihesii^ 

 Syrphus balteatus, and Catabomba pyrastri. 



The species that is most common, or which was the most 

 common during the summer and autumn of 1898, is Syrphus 

 ribesii. There are three or four species which are veiy much 

 alike, and are known as the ribesii group, but each has dis- 

 tinctive characteristics, and the insect described here is the 

 Syrphus ribesii proper, as defined by Meigen. It is nearly 

 half an inch long with awing expanse of close on an inch, 

 The head is bright yellow, with reddish black antennge, 

 the third joint of which is pale underneath, and copper 

 coloured eyes, the legs are ochreous, with the tarsi black 

 or reddish black. The thorax is dull green, and the 

 abdomen, which is broader in the middle part, is black, having 

 black hairs and four honey-yellow bands crossing it, slightly 

 notched or nicked with black. The wings are clear, but have 

 dark yellow borders. The male is rather smaller than the 



