INSECTA. 



253 



wise two muscles, so disposed as move the Fig. ill. 



entire tarsus and foot. The extensor (f) of 

 the tarsus is the smallest ; it arises from the 

 lower half of the interior of the tibia, and is 

 inserted into the margin of the first joint of 

 the tarsus : but the flexor of the foot (c), aris- 

 ing from the upper half of the cavity of the 

 tibia, ends in a delicate tendon, which passes 

 through all the tarsal segments, to be fixed to 

 the flexor tendon of the claw-joint upon which 

 it acts ; and, as it traverses the penultimate 

 joint, it receives the fibres of an accessory 

 muscle (d). The extensor of the claw (e) 

 is likewise placed in the penultimate tarsal 

 segment, and strikingly exhibits, by its small 

 comparative size, the feebleness of its action, 

 when compared with the flexors of the same 

 joint. 



It would be superfluous to describe more 

 in detail the disposition of individual muscles, 

 as the above example will abundantly suffice 

 to give the reader an idea of the general ar- 

 rangement of the muscular system, not in in- 

 sects only, but in all the ARTICULATA provided 

 with jointed extremities. 



(294.) The substances employed as food by insects are various, 

 in proportion to the extensive distribution of the class. Some de- 

 vour the leaves of vegetables, or feed upon grasses and succulent 

 plants ; others destroy timber, and the bark or roots of trees ; while 

 some, more delicately organized, are content to extract the juices of 

 the expanding buds, or sip the honeyed fluids from the flowers. 

 Many tribes are carnivorous in their habits, armed with various 

 weapons of destruction, and carry on a perpetual warfare with their 

 own or other species ; and again there are countless swarms ap- 

 pointed in their various spheres to attack all dead and putrefying 

 materials, and thus to assist in the removal of substances which, by 

 their accumulation, might prove a constant source of annoyance 

 and mischief. Such differences in the nature of their food demand 

 of course corresponding diversity in the construction of the in- 

 struments employed for procuring nourishment, and accordingly 

 we find in the structure of the mouths of these little beings innu- 



