DIPTERA ' 211 



he sees it, but he may give that name to any of the following 

 distinct species: — (i) Musca domestica, the true house-fly; 

 (2) Homalomyia scalaris, very plentiful from early summer to 

 late autumn, a little smaller than the last, and identified by a 

 tubercle on the inner side of the middle tibia ; (3) H. canicu- 

 laris, known by a yellow patch on the side of the first and 

 second abdominal segments ; (4) Cyrtoneura stabulans, a 

 grey fly with reddish legs, rather larger than the house-fly ; 

 (5) Stomoxys calcitrans, the stable-fly, armed with a proboscis 

 which can pierce the human skin. In spite of a general 

 resemblance which deceives all but a practised observer, there 

 may be marked differences of habit, and the larvae may differ 

 greatly, not only in mode of life and choice of food, but in 

 appearance and structure. 



The gout-fly (Chlorops taniatus) is a Muscid, whose larva 

 does great damage to barley, and sometimes to other grain. 

 It is believed to be particularly prevalent on wet land, and to 

 attack late-sown crops with more effect than others. The 

 damage is done to the ear, which does not unfold, but remains 

 enclosed in its sheath. On examination a furrow is seen to 

 run along one side of the ear down to the base of the enclos- 

 ing leaf, and here the full-fed larva or the pupa will often be 

 found. The larva is yellowish, and shaped like a blow-fly 

 maggot with narrow head-end and broad tail-end ; it is small, 

 only attaining a length of 6 mm. The pupa is red or brown, 

 somewhat flattened, and enclosed in the hardened larval skin, 

 as in all the more specialised Diptera. The fly appears at 

 harvest ; it is 3-4 mm. long, yellow, but with three dark stripes 

 running lengthwise along the thorax, and four dark transverse 

 stripes on the abdomen. The male has the abdomen blunt 

 at the end, while it is pointed in the female. The wings are 

 longer than the body. It is probable that the autumn eggs 

 are laid in wild grasses, and that the females of the spring 

 brood lay their eggs in the young barley-head. 



The frit-fly {Oscinis frit) is a small black fly which attacks 

 oats and sometimes barley, the larva devouring the heart of 

 the young shoot, so that the plant turns brown and withers. 



The CEstridas (bot-flies) are large flies, with very short sunk 

 •antennas, the proboscis and mouth-parts usually vestigial. The 

 winglet is often large and hides the haltere. The larvae are 

 parasitic on marnmals. 



