FUNCTION OF MOTION. 23 



make the most of their brief and uncertain existence. Witness the energy of the dung- 

 beetle in finishing the ball in which it has deposited its egg : it often dies in the act of 

 providing for the continuance of the life of its kind. To some these actions may seem less 

 interesting, because instinctive ; but surely the faculty of instinct affords matter for deep 

 thought to the ordinary observer, and to the philosopher it must possess an interest next to 

 that of reason itself. Instinct urges the individual forward to the fulfilment of its destiny, 

 but it makes no inquiry as to the cost. 



Mi sci Lab motion. The insect enjoys a full development of the power of motion, 

 especial ly in its perfect state : the two kinds of muscle, striated and non-striated, are al- 

 ways present. Every part of the system is supplied with muscular fibres ; not only are the 

 legs and wings largely supplied with them, but also the abdomen and various parts of the 

 trunk, head, and thorax. The most interesting fact which appears in this connexion, is the 

 power of the insect Jo sustain a long and vigorous flight -. thus the dragonfly darts for- 

 wards, backwards, or sideways, and is able to outstrip the swallow in its most rapid course ; 

 and this it can do for hours together. Taking into consideration the diminutive size of 

 insects, we readily see, that in proportionate locomotive power, they far excel the verte- 

 brate animal. We have already observed that their joints usually admit of but two kinds 

 of motion, forwards and backwards, or the ginglimus movement : when, however, this 

 motion is exerted in extension and flexion, as in the leaping of the grasshopper or flea, we 

 cannot fail to perceive that their powers in this respect, also as in flying, are far superior 

 to those possessed by any other class of animals. 



Though the larval state of insects is generally sluggish, we are not without many 

 examples where there is a great degree of activity. We often see the caterpillar hurrying 

 along as if it were in great haste, though the space it is able to traverse is quite limited. 

 We observe, in all these movements, an aim to preserve life : the life of self, however, is 

 subordinate to that of kind or progeny. 



Propagation. Insects propagate their kinds from eggs laid by the female, subsequent 

 to the act of congress with the male : the sexes are therefore distinct. Their power of 

 multiplication is immense, especially in those insects which produce several broods in a 

 season. But there is a remarkable exception to the foregoing rule : the aphis increases by 

 a process of gemmation ; females being cast off at once for several generations, of which 

 each possesses the power of multiplying its kind in the same way. Carpenter likens it to 

 the gemmation of the polypi, " the individuals being budded off from internal stolons, 

 instead of being developed from ova provided by the female and fertilized by the male." 

 It has long been known, that in the aphis, this method of propagation is repeated to the 

 seventh or ninth generation. At the end of the season, the perfect individuals, both male 



