REFLEX AND CONSENSUAL ACTIONS OF INSECTS. 487 



truly rational character. When we attentively consider the habits of 

 these animals, we find that their actions, though evidently directed to 

 the attainment of certain ends, are very far from being of the same 

 spontaneous nature, or from possessing the same designed adaptation 

 of means to ends, as those performed by ourselves, or by the more in- 

 telligent Yertebrata, under like circumstances. We judge of this by 

 their unvarying character, the different individuals of the same species 

 executing precisely the same movements when the circumstances are 

 the same ; and by the very elaborate nature of the mental operations 

 which would be required, in many instances, to arrive at the same 

 results by an effort of reason. Of such we cannot have a more remark- 

 able example, than is to be found in the operations of Bees, Wasps, 

 and other social Insects ; which construct habitations for themselves, 

 upon a plan which the most enlightened human intelligence, working 

 according to the most refined geometrical principles, could not surpass ; 

 but which yet do so without education communicated by their parents, 

 or progressive attempts of their own, and with no trace of hesitation, 

 confusion, or interruption, the different individuals of a community all 

 labouring effectively for one common purpose, because their instinctive 

 or consensual impulses are the same. 



861. It is interesting to remark that, in the change from the Larva 

 to the perfect or Imago state of the Insect, the Cephalic ganglia 

 undergo a great increase in size. (Plate II., Fig. 3, a, a.} This 

 evidently has reference to the increased development of the organs of 

 special sense in the latter; the eyes being much more perfectly 

 formed ; antennae and other appendages used for feeling being evolved ; 

 and rudimentary organs of hearing and smell being added. In 

 respondence to the new sensations, which the animal must thus 

 acquire, a great number of new instinctive actions are manifested; 

 indeed it may be said, that the instincts of the perfect Insect have 

 frequently nothing in common with those of the Larva. The latter 

 have reference to the acquirement of food ; the former chiefly relate 

 to the acts of reproduction, and to the provisions requisite for the de- 

 posit and protection of the eggs and the early nutrition of the young. 

 We find another important change in the nervous system of the 

 adult or perfect. Insect ; namely, the concentration of the ganglionic 

 matter of the ventral cord in the thoracic region (0, /) ; with the three 

 segments of which, the three pairs of legs and the two pairs of wings 

 are connected. The nine segments of the 'abdomen, in the perfect 

 Insect, give attachment to no organs of motion, and are seldom them- 

 selves very moveable ; and we find that the ganglia which correspond 

 with them have undergone no increase in size, but have rather dimi- 

 nished, and have sometimes almost completely disappeared. Where 

 the last segment, however, is furnished with a particularly moveable 

 appendage, such as a sting, or an ovipositor, we always find a large 

 ganglion in connexion with it. 



862. These ganglia of the ventral cord evidently correspond in 

 function with the pedal ganglion of the Mollusca; being so many 

 repetitions of it ; in accordance with the number of members. We 

 have now to speak of a system of respiratory ganglia, which also are 



