Chapter 15. 



INJURIOUS INSECTS [Continued). 



Crane Flies; the Pear Midge; the Celery Fly; the Cabbage 

 Root Fly; the Onion Fly; the Narcissus Fly; the House Fly. 



In this lecture we are concerned with the order Dipt era 

 which comprises the true Flies. These Insects can be 

 recognised by the presence of a single pair of wangs, the 

 hinder pair being absent, and only represented by curious 

 knobbed organs known as halteres or balancers. The 

 larvae of the Diptera are devoid of true limbs and are 

 commonly known as maggots. A pupa stage is always 

 present and, in a very large number of species-, the skin 

 of the larva is retained, forming a hardened case or 

 puparium enclosing the true pupa. Although no aclult 

 Flies are directly injurious to vegetation, certain kinds 

 such as Mosquitoes, Sand Flies, and Tsetse Flies are 

 injurious to man. They pierce the skin in order to suck 

 his blood and thereby act as carriers of the organisms of 

 some of the most virulent diseases. 



Some of the most familiar of the larger Flies are the 

 Daddy Long Legs,'' or Crane Flies {Tifula oleracea and 

 allied species) (13). Although they are commonly pests 

 of our meadows and cereal crops nevertheless they not m- 

 frequently injure turnips, peas, beans, cabbages, hops, 

 dahlias, carnations and odier garden plants. Their larvae 

 are commonly known as leather jackets,'' and when fully 

 grown they attain a length of i|in. In colour they are 

 dull grey or brown and are not unlike fragments of small 



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