HEAD OF RHINGIA, OR SYRPHUS. 75 



small ; so is the fifth, and the others are like little spines ; 

 nevertheless they are seven in all. The eyes are prominent 

 and oblong ; but the eye of the Ply is particularly described 

 in the head of Rhingia. 



HEAD OF RHINGTA, OR SYRPHUS. 



This beautiful preparation is the one I have chosen for 

 drawing particular attention to the eye of the Fly. That 

 fine delicate lace, now perfectly transparent, is the skeleton 

 or framework in which were set four thousand perfect organs 

 of sight, which we call the eye of a Ply. That outer mem- 

 brane, which is all that is now left, is the cornea ; it was 

 lined with an intense black pigment, excepting one tiny 

 spot in the centre of 'each facet, through which the light 

 was admitted. Behind the pigment was a broad zone, 

 orange-coloured and black ; then a second zone, deep blue 

 or black; then the optic ganglion, gathering all -the fila- 

 ments of each eye into one knot the brain. 



The brain of* insects is not a solid mass, or great ganglion, 

 like the brain of animals ; but the medium of communica- 

 tion between insects and the external world, is a nervous 

 system consisting of two medullary threads or cords, and a 

 series of knots or ganglia placed at intervals throughout 

 the body. 



Larvae have usually two of these gangHa to each segment 

 of the body. The perfect insect has fewer ; but the first 

 ganglion, as in the Fly/ always sends out the nerves of the 

 eyes, tongue, maxillae, mandibles, and antennae. Therefore 

 we understand how the organs of sight are united in the 

 head of a Fly upon therfirst ganglion or brain. And whilst 

 each eye receives a perfect image of the object before it, one 

 single impression may be conveyed to its possessor. 



This head of Rhingia has also a very beautiful tongue, 

 long and slender, lobed and edged with spiral fibre, capable 

 of great extension to accommodate the habits of the Fly. 



The Rhingia campestris, or Rostrata, is so called from 

 its projecting horny beak. It is a very pretty Fly com- 

 mon in woods and gardens during the Summer ; remarkable 

 from its hovering like a Humming-bird over the flowers, 



