THE DIPTEItA OP GUERNSEY. 55 



In warmer countries the mosquitoes are so troublesome as to 

 require special means of protection from their weapons ; and 

 we have all read of the dreaded tsetse fly of certain regions 

 in Africa, which is so deadly to horses. The great majority 

 of species, however, living as they do on decaying matter, are 

 of the utmost use as scavengers, especially in hot countries. 

 It has been stated on good authority that three Blue-bottle 

 flies will eat up the carcase of a dead horse as quickly as a 

 lion would ; meaning that the eggs they would deposit therein 

 would be so numerous, and so soon be hatched and become 

 larvee, that the carcase would be devoured in an incredibly 

 short time. So prolific are these little creatures that no less 

 than 20,000 eggs have been counted in the ovary of a single 

 female. 



Until recently the fleas have been classed in a separate 

 order under the name of Aphaniptera, but they are now gene- 

 rally included among the JDiptera, on account of the similarity 

 of their transformations and their possessing scales represent- 

 ing rudimentary wings and halter es, besides other resem- 

 blances. 



In the arrangement of my list I have followed the most 

 recent classification, that of Mr. G. H. Verrall's " List of 

 British Diptera," published in 1888. 



I will now give a short description of the principal fami-* 

 lies into which the order is divided. 



The first family consists of the Pzdicidce, or Fleas. Of 

 these I know of four species in Guernsey, and probably there 

 are more. There is no need to describe them, as the type 

 Pulex ir ritans is well known, and they all bear a family like- 

 ness. 



The CecidomyidcB) or Midges, many of which occur with 

 us, do not figure in the present list. All of them are small 

 insects, many being exceedingly minute, and require special 

 study to name them correctly, the species being so closely 

 allied. The larvae live in various plants, one, the dreaded 

 Hessian fly, Cecidomyia destructor, being very destructive to 

 wheat ; others form galls on plants. 



The Mycetophilidce, or Fungus gnats, the larvae of which 

 feed on rotten wood, rotten fruit, fungi, &c, are rather small 

 and of delicate structure. 



The BibionidcB, or Garden flies, are small dark insects fre- 

 quenting meadows and often appearing in immense numbers. 



Bibio marci is a well-known species. It is of a deep 

 black colour, and appears on our cliffs in immense numbers on 

 about St. Mark's Day, hence the name. 



