THE DIPTERA OF GUERNSEY 



BY MR. W. A. LUFF. 



The order of insects named Dipt era, or two-winged flies, 

 contains a very large number of species. The number 

 recorded for the British Islands alone is about 3,000, and the 

 total number in the whole world will probably exceed 30,000. 



There have been few orders of insects so neglected as 

 the Diptera, for although some of the species are very elegant 

 and beautiful in the perfect state, still the great majority are 

 small in size and sombre in colour, and do not attract begin- 

 ners in the science, like such insects as butterflies and moths. 

 The life histories of these insects are, however, so interesting 

 and varied that a study of even a few species will well repay 

 the observer. 



The larvae of Diptera are footless grubs, or maggots, 

 their food usually consisting of decaying animal and vegetable 

 matter. Some, however, mine the leaves of various plants, 

 others, as the dreaded Hessian fly, on which whole volumes 

 have been written, live on and destroy our cultivated plants. 

 Several families pass their preliminary stages in the waters of 

 stagnant ponds and ditches, whilst others are parasites living 

 within the bodies of other insects, especially of the Lepidop- 

 tera. 



In structure the Diptera, in the imago or perfect state, 

 are distinguished from other orders of insects by having two 

 wings only and a pair of small knobbed appendages just 

 behind them, which are called halteres or poisers. The wings 

 are membranous, and when at rest remain expanded, as in the 

 Hymenoptera ; that is, they are never folded upon themselves. 



The jaws of Diptera are never formed for biting or nip- 

 ping. The mouth has a fleshy proboscis, which is really a 

 modified labium or lower lip. This proboscis encloses several 

 lancet-like organs, capable of penetrating flesh or the softer 

 parts of vegetables. The mouth is therefore called suctorial. 



It is scarcely necessary to say that many of the Diptera, 

 though small in size, are great annoyances to man and animals. 



