206 DIPTEKA OR TEUK FLIES. 



The majority hatch out in the autumn. The grubs are called 

 " Leather-jackets " (fig. 99, 4), on account of their tough skin, 

 which is brown and wrinkled. They have a blunt anal 

 extremity, which has a few blunt finger-like processes on it. 

 The roots of practically all plants are attacked by them, and 

 eaten away so as to kill the plant. The pupse are brown (fig. 

 99, 5), and provided with circles of spines ; the head has two 

 curved horns (palpi cases). We find them quite deep in the 

 ground, forcing their way up when ready to emerge by means of 

 the spines, untU half the pupal case projects out of the earth, 

 when the shell splits and the fly emerges, soon to deposit 

 fresh ova. Another species, called the Spotted Crane-fly {T. 

 maculosa), also helps T. oleracea to do mischief. 



Prevention and Remedies. — Gas -lime is very injurious to 

 these grubs, and may be well employed on land when it is 

 infested with " Leather-jackets." It is especially valuable put 

 upon mould and leaf-heaps, where crane-flies lay their eggs 

 abundantly, as a preventive of oviposition. The drainage of 

 damp land often checks their presence. Brush-harrowing grass 

 land when we see the flies about is advantageous, as it disturbs 

 and crushes the eggs laid by the female. It is said that the 

 larvae come out on to the surface at night, and that rolling with 

 a Cambridge ring-roller then does much good by crushing them 

 on the top. Birds are the great natural check of this pest, 

 those that are beneficial being mentioned in another chapter. 



"Winter-gnats (Trichoceha hibmalis and T. rbgelationis). 



These delicate little Tipulidse (fig. 100) are found dancing in 

 the air in clouds in the winter months whenever the air is 

 warm. They are brownish grey, with four brown stripes on the 

 thorax, T. hiemalis having spotless wings, while T. regelationis 

 has a dark spot on each wing at the cross veins. The larvae live 

 in rotting turnips ; they are cylindrical, and taper to a point at 



