150 



GRAMMAR OF ENTOMOLOGY. 



series of corcula is under the view, it assumes the 

 appearance of an undulating line, the dilated 

 portion passing upwards by the most regular pul- 

 sation : the rate being in the larvae we have most 

 examined, (that of an ephemera?) about sixty 

 pulsations per minute. 



567. When the twelfth corculum 

 has attained its state of greatest 

 dilatation, the anterior portion, is 

 forced upwards by the commencing 

 dilatation of the thirteenth, and by 

 this movement the mouths of the 

 ~u lateral veins are completely closed, 

 the blood continuing to flow up wards 

 from the thirteenth corculum only. 

 Fig. 3 represents the twelfth and 

 thirteenth corcula in this state. 



568. The whole of the blood thus received from 

 the veins into the corcula, and by one corculum 

 from another, passes upwards towards the head of 

 the insect, and, therefore, the only arteries issue 

 from the first or anterior corculum. 



569. From this corculum, arteries proceed to 

 all parts of the body ; minor ones supply the head 

 and antennae, while major ones turn downwards 

 through every part of the insect, terminating in 

 the lateral regions of each segment, and here, 

 through the medium of the organs of respiration, 

 communicating with the air. 



570. The course of arteries on each side of the 



