82 INSECTS 



the ground; the larva starts its feeding there and 

 causes an injury which the plant, in its efforts to repair, 

 marks by an enlargement. A midge lays its eggs in 

 the tip of a willow shoot, the larvae feed at the base 

 of the forming leaves and the plant becomes crippled, 

 producing a cabbage-like head instead of a shoot with 

 developed foliage. And so we have every gradation 

 from a feeding without any perceptible enlargement 

 or swelling at all, to a well-formed abnormity formed 

 by a crippling of the natural growth, and not a distinct- 

 ly separate structure, unrelated to normal growth. 

 There are other types of midge-galls, like those on the 

 grape, which are mere fleshy swellings of the normal 

 tissue, and sometimes more characteristic enlargements 

 of infested twigs; but generally no separable galls. 



As to the actual injury caused, that varies enor- 

 mously. Many of the midge-galls cause no real or per- 

 manent injury whatever to the plant attacked. Others 

 destroy either the plant or the seed beyond all chance 

 of recovery. These midges are to be accounted among 

 the most serious plant enemies, although soft her- 

 baceous plants and grasses are more apt to suffer; 

 very few of them occurring in genuinely woody tissue. 



Among the Muscid flies resembling in general type 

 and appearance the house-flies, the Anthomyiids are 

 the most troublesome and dangerous. They attack 

 a very great variety of plants and may be miners in 

 the thick leafed forms like beets, or feeders in roots 

 like those of the radish, cabbage or onion. And these 

 root maggots are very generally fatal to the plant 

 attacked, so that their rank as destroyers is high. 

 The maggots themselves differ very little from the 

 other Muscid larvs; in fact not at all to ordinary view, 

 and they gain their food in the same way by scraping 

 and disintegrating the tissue and then absorbing the 



