1909O The Insect and Alli-ed Pests of the Hop. 567 



Black or Fever Flies (Bibionidce). 



At least three species of Bibionidce are, in their maggot 

 stage, to be found attacking hops. 



These flies (PI. I., Fig. 5) are quite harmless in the 

 adult condition, but the larvas feed on the roots of 

 hops, and frequently kill the sets outright. Damage to 

 hops has been reported to me from Kent, Surrey, 

 Hants, and Worcester. All three species bred from hops 

 (Bibio marci, B. hortulanus, and Dilophus febrilis) feed on 

 all manner of roots, beside those of the hop. These 

 grubs (PL I., Fig. 4) resemble small Leather Jackets (p. 566), 

 but may be recognised at once by the fleshy spines or processes 

 at the sides of the body and on the back. They usually occur 

 in masses or in groups not far from one another; in hops 

 they occur mainly in a group close around the centre of the 

 hill. Whilst the weather is not too cold they remain feeding 

 all the winter into the spring, when they pupate in the soil 

 and appear as winged insects early in the year. 



Sometimes these black flies occur in swarms. Ormerod 

 records Dilophus febrilis, or the Fever Fly, in vast numbers 

 collecting in hop cones at Rainham, but they were doing 

 no damage. This species occurs first in May and June and 

 then again in August, but the two Bibios in May and June 

 only. Whitehead mentions cones being sent to him from 

 the neighbourhood of Maidstone full of these flies, and which 

 he said "had evidently much injured the cones." One cannot 

 see how they can have done so unless they died in the 

 cones and were so preserved in drying. The adult fly is 

 black in the male, paler in the female, and is about \ in. 

 long. The grubs are dirty white, with brown heads, and 

 are about \ in. long. The pupae are pale brown in colour. 



Bibio hortulanus, Linn., is black in the male, with greyish 

 wings, whilst the female has the thorax and abdomen tawny, 

 the former black in front and at the sides, the head and legs 

 black, and in length it reaches J in. 



B. marci, Linn., is black in both sexes. The larvae of 

 these two are slaty in colour, and are figured natural size. 



Fortunately, these grubs can be easily trapped by placing 

 rotten roots in the hills, and both soot and lime are very 



