MICROSCOPIC DRAWING AND ENGRAVING. 



body of the insect. The length of the eggs varies from the 40th to 

 the 50th of an inch. 



In the larva (fig.l) the obvious and curious parts are the 

 kidney-shaped bodies, b and rf, two of which are situated near the 



Fig. 30. 



head, and the other two in the third division from the lower 

 extremity. The first pair are inclined towards each other, while 

 the others lie in parallel planes, as represented in the plan, or 

 bird's-eye view, drawn of the natural size in fig. 3. ^ Physiologists 

 have not ascertained what may be the functions, performed by 

 these singular organs : it is worthy of remark, however, that a 

 similar structure is observable 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 motion 

 in different directions, and, like the reniform bodies, 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 shown of the full size in fig. 3, is examined 

 from above, it exhibits the position and decussation of the various 

 muscles lying along the back, which are observed to cross at the 

 joints, and at points situate midway between them. 



The alimentary canal appears to contain some particles of a 

 pinkish coloured matter : 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 rapidly changes to the 

 pupa, shown in the drawing (fig. 2). When it is desirable to 

 92 



