HOUSE FLIES AND BLUEBOTTLES 



187 



there is a small raised area, in which are situated three 

 shining hemispherical knobs of a ruby-red colour. 

 These are the simple eyes, or " ocelli " (Fig. 60). They 

 are placed so as to form a triangle with the apex point- 

 ing forwards, an arrangement in which, as already 

 pointed out, flies resemble bees, wasps, and other 



FIG. 59. Head of Bluebottle, the hairs having been removed. 

 e, eyes; a, antennae; p, proboscis partly unfolded ; m, maxillary palpi. 



Hymenoptera. In the centre of the triangle two stout 

 bristles stand more or less erect, like guardians of the 

 ocelli, as perhaps they are, and others, larger still, stand 

 facing one another at the sides, forming the commence- 

 ment of two rows, which run down the face. Quite a 

 forest of much smaller bristles rise amongst the ocelli, 



