THE HOP PLANT. 63 



being killed by suction, not eaten bodily. When the larva 

 is full grown it passes into the pupal state, and very soon 

 the perfect insect makes its appearance, and lays eggs in its 

 turn, several generations being produced in the course of a 

 year. The number of aphides which a single larva is capable 

 of destroying is very great. 



The larvas of the genus Hemerobius, the pearl fly, are also 

 useful in a similar way. 



2. A more dangerous enemy to the aphis is the larva of 

 the moon-spot hovering fly, Syrphus seleniticus, a greenish grey 

 legless maggot which also kills by suction. 



3. The Goocinella, or lady-bird tribe, are very beneficial, 

 especially the larvae, the chief aphis-hunter among them being 

 the larva of Coccinella septempunctata, the common lady-bird. 

 This larva is provided with six legs, and is greyish black in 

 colour, the head and belly being yellowish ; it inhabits the 

 under side of the hop leaf, and devours the hop lice by thou- 

 sands. The chrysalis is hairless, smooth, and dotted with 

 black spots on a yellow ground. Several generations are 

 produced during the year, and, on account of its great use- 

 fulness, this insect deserves to be carefully protected in all 

 hop gardens. 



4. Acarus coccineus, a kind of mite, also pursues the aphis 

 and kills it by suction. 



5. Ichneumon flies lay their eggs in the living bodies of the 

 larvae of moths, etc., injurious to hops, and should, therefore, 

 be protected. 



Fruwirth says that the insects inimical to hop pests should 

 be purposely introduced into hop gardens. The lady-bird, for 

 instance, is found in large numbers on the sallow {Salix 

 caprea), and is easily caught in an inverted umbrella, etc. 



