OF INSECTS. 107 



similar to the horns of quadrupeds, the spurs of the cock, the poisoning 

 teeth of vipers, &c. ; but there is a singularity attending the possession of 

 those weapons in the insect that is not in the other animals. In other 

 auimals these weapons of simple offence are either common to both male 

 and female, or are peculiar to the male, so that there are more males in 

 possession of such weapons than females. And in those animals where such 

 weapons are common to both sexes, and are used for offence and defence, 

 the males have them better fitted for action than the females. The tusks 

 and claws of the lion, the tusks of the boar, the horns of the bull and ram, 

 antlers of the stag reindeer, are all better fitted for action than those in 

 the lioness, the sow, the cow, the ewe, the hind of the reindeer, &c. But 

 weapons of offence are so peculiarly wanted by the male, that many 

 males have them and the females not ; such weapons are the horns of 

 the buck, the spurs of the cock, the tusks of the horse ; so far then the 

 males have the superiority in point of offensive and defensive weapons ; 

 but this is not the case with insects, for the females possess the weapon 

 in many kinds where it is peculiar to one sex. 



Of the Heart and Blood of Insects. 



The heart of the caterpillar runs all along the back its whole length. 

 [When it acts] it begins to contract at the tail of the animal, and the 

 contraction runs from thence to the head : it can be traced all along by 

 the eye. 



The circulation of the insect is probably veiy slow, if we may 

 judge of the whole class by the motion of the heart in the caterpillar. 

 In the silk- worm, for instance, the heart beats only 34 in a minute : 

 however, I have known in the adult human the pulse as low, when in 

 visible health ; and this for many years. The blood in the winged 

 insect must be small in quantity, for when we open any one, we hardly 

 observe any moisture. But, as an insect has two active states, viz. the 

 maggot, and the complete, or fly-state, we find the blood very different 

 as to quantity in these two states. In the maggot or caterpillar it is 

 large in quantity ; in the fly- state it is hardly perceivable : this last 

 circumstance takes off weight in flying. 



Of the Circulation in Insects. 



The circulation of the blood in the insect is in itself very simple ; 

 yet from our being very familiar with the most complicated, viz. that 

 in the Tetracoilia, it at first might seem complicated. 



Insects may be said to have neither pulmonary arteries nor veins, 

 having but one simple circulation ; nor can they be said to have one 



