FRUIT FLIES 39 



naked eye, the full-grown maggot being about four- 

 tenths of an inch in length. A feature of this maggot 

 not generally known is that it is an air-breather, and 

 that, if air be excluded from the fruit, its inhabitants 

 must die. The chrysalis is one-fifth of an inch in 

 length, and exists in a partly comatose condition till it 

 develops into the fly. The male is easily distinguished 

 from the female, as the posterior of its body is rounded, 

 while that of the female carries the ovipositor, the 

 pointed projectile being used to pierce the skin of the 

 fruit and deposit the eggs in the tissue. The ovipositor 

 can place an egg one twentieth of an inch below the 

 surface. When disturbed it does not fly far ; but tries to 

 hide beneath the leaves, and for this reason often goes 

 unobserved." Mr. Tryon concludes that the average 

 life of the insect is about five weeks, and that each fly 

 lay about a dozen eggs. 



When fruit is easily punctured the fly distributes its 

 eggs, though many (but occasionally eight), and even 

 the whole batch, are placed in one fruit. It is not usual 

 to find eggs laid in fruit before it is two-thirds grown, 

 as the female seems to defer operating till a pleasant 

 odour from the fruit is perceptible. 



Regarding the periods of development at' which the 

 fruit is attacked, Mr. Tryon, together with Mr. Searle, 

 furnished some reliable information. "The eggs take 

 three days to hatch when under observation, but in the 

 open air this will be hastened or retarded by climatic 

 conditions. Occasionally the young grubs are killed 

 because the growing fruit presses upon them, and in 

 other cases the young are unable to break down the 

 tough woody tissue of immature fruit. In mellow 

 saccharine fruits all the eggs hatch out, and the grubs 

 mature unless the tunnel becomes closed and excludes 

 the air. In pip fruit and slipstone peaches the grubs 

 can live nearer the centre, but in close stoned fruit they 

 must work near the surface. 



( The life of the grubs in the fruit is from two to five 



