12 COMMON BRITISH INSECTS. 



of the butterflies ; but for this purpose, a careful 

 manipulation of the microscope is needed. 



In addition to these compound eyes, many insects 

 possess several small simple eyes, called ocelli. They 

 are very small, and in the Beetles are two in number, 

 and placed on the back of the head. 



Having examined the head, we now take the next 

 division of the insect, namely the thorax. This im- 

 portant part bears all the instruments of locomotion, 

 whether they be legs or wings ; and is most wonder- 

 fully constructed for the purpose, being supplied in 

 the interior with hard projections that are needed for 

 supporting the powerful muscular apparatus needful 

 for flight, and the less powerful, but still more important 

 system by which the legs are moved. 



The thorax is internally divided into three parts, 

 which we call prothorax, or front thorax ; meso- 

 thorax, or middle thorax ; and metathorax, or hinder 

 thorax. Beginning with the prothorax, we find it 

 again divided into two portions, the upper and the 

 lower the former going by the name of pronotum, 

 i.e. in front of the back, and the other called pro- 

 sternum, i.e. in front of the breast. Fig. 7 shows the 

 pronotum of the Stag Beetle : 7 aa are the lateral 

 margins, *jb is the anterior margin, Jcc are the pos- 

 terior angles, jd the posterior margin, and Jee the 

 anterior angles. 



Next we come to the prosternum, which is shown 

 at Fig. 8 ; 8a being the sternum, and %bb the insertion 

 of the coxa, a joint which will be presently described. 



The mesothorax with the abdomen is shown at 

 Figs. 9 and 10, the former exhibiting the upper, and 



