330 



BENiiFiciAL Insects. 



female, and, as in most of the Syrphidce, the eyes of the male 

 (No. i) meet on the front, but are distinctly apart in the 

 female. Eggs are laid singly, upon leaves infested with 

 aphides, and from them larv^ quickly come. The larva 

 (No. 2) is of a dirty yellow colour, long, with a tapering head, 

 and its mouth is furnished with a three-pronged harpoon for 

 transfixing its prey. The body is flask-shaped at the hinder 

 end, and smooth, with a somewhat transparent skin and a few 

 transverse lines. It has no legs or eyes, and thrusts out its 

 \ long neck on every side in search of its prey, which it 



instantly harpoons and holds up in the air, shaking it as a 

 dog shakes a rat. The quantity of aphides killed and eaten 

 by one of these larvae is incredible. Curtis says that one will 

 devour 100 in an hour. All kinds of aphides appear equally 

 acceptable to these larvae. Some kept in a glass case were 

 fed with the aphides of the turnip, rose, hop, geranium, apple, 

 plum,currant, lime, and carrot, and they devoured them quite 

 indiscriminately. In from twelve to fifteen days the larva 

 attaches itself to the leaf or stalk of the plant on which it has 

 lived, and changes to a flask-shaped pupa within its own skin. 

 The pupa (No. 3) is of a dull brown hue, with indistinct spots 

 upon it. There are at least two generations of this insect 

 during the summer. In a season like that of 1898, when 

 aphides of all kinds were unusually abundant, there appeared 

 to be three, or more, generations. The pupae are seen not only 

 on the leaves, but also upon the stems or stalks of plants, 

 and might be safely preserved on these during the winter. 

 Those on the leaves fall to the ground and are probably 

 destroyed, but it would appear that the hibernation of 

 the insect has not been clearly ascertained. Large swarms of 

 these flies are constantly seen in the autumn, which lead to 

 the supposition that, as in the case of wasps and some flies, 

 hibernation may take place in the perfect state. There are 

 such immense quantities of these flies at the beginning of the ' 

 summer, and their appearance is so early, that it would 

 almost appear as if this were so. Dr. Meade, the well-known 

 dipterist, however, does not think that this form of hiberna- 

 tion prevails with the SyrphidcE. It has been noticed that 

 pairing occurs among the flies in the swarms during the 



