STRAW-COLOURED GNAT. 53 



by these singular organs : it is worthy of remark, 

 however, that a similar structure is observahle in the 

 tadpole, and figured in Sir Everard Home's Lectures on 

 Comparative Anatomy*. The other parts of its structure, 

 which appear equally singular and curious, are a number 

 of globules, a, which are situated near the first pair of 

 bodies, b. These globules have a slight oscillatory mo- 

 tion in different directions, and, like the reniform bo- 

 dies, seem to have a metallic lustre, but are not opaque. 

 From the exquisite polish of these globules, they reflect 

 the forms of surrounding objects, as window-bars, &c. 

 which are indicated in the drawing by small squares, 

 resembling the images formed by convex mirrors. 



When the larva (as shewn of the full size in fig. 3) is 

 examined from above, it exhibits the position and decussa- 

 tion of the various muscles lying along the back, which 

 are observed to cross at the joints, and at points situated 

 midway between them. 



The alimentary canal appears to contain some particles 

 of a pinkish coloured matter, and has a slight peristaltic 

 motion : but every part of the object, as seen beneath the 

 microscope, is so accurately noted in the drawing, that a 

 more minute description must be deemed superfluous. 



If the insect have a sufficient supply of food, it only 

 continues for a few weeks in the larva state, when it ra- 

 pidly changes to the pupa, shewn in the drawing, fig. 2. 

 When it is desirable to preserve it for the microscope, 



* Vol 6, Sup. Plate 56, fig. 4, D. 



