174 ANATOMY. 



whereas in the abdomen there are many spiracles, but proportionally 

 fewer internal parts. The vessels of the thorax consequently belong 

 more to the organs of motion, and those of the abdomen to the intes- 

 tinal canal and the sexual organs. 



Two of the many branches which the main stem of the first thoracic 

 spiracle sends off always go to the head. One runs superficially over 

 and contiguous to the mandibulary muscles, and also unites to its oppo- 

 nent upon the opposite side (Melolontha) , and distributes itself with 

 its branches to all the superior internal portions of the head. From it 

 the ring encompassing the eye proceeds, or, where this is wanting, the 

 branches which spread in the pigment of the eye. The inferior branch 

 accompanies the nervous cord and the oesophagus into the head, and 

 distributes itself to the lower lying muscles, the maxillae, and the 

 labium. A third branch, which descends downwards anteriorly, or as 

 in the Mantodea, two equal branches spreading in this direction pass 

 into each anterior leg, and each distributes itself with innumerable ra- 

 mifications to its very point. The extreme posterior branch is the one 

 connecting it with the second thoracic spiracle, the remainder origin- 

 ating between this and the beforementioned one, distribute themselves 

 to the muscles, and several pass into the meso-thorax. The spiracle 

 between the meso- and meta-thorax, generally the smallest, has also 

 the fewest branches, namely, besides the connecting ones which unite 

 it to the first and third spiracle, it has a main branch for the middle 

 leg, and several ramifications for muscles. From the third spiracle 

 between the meta-thorax and the abdomen it is generally that the 

 greatest number of branches originate, namely, the two connecting 

 branches, the branches for the third pair of legs, and several large 

 ones to the muscles. The spiracles of the abdomen have each their 

 two connecting branches, and besides which several ramifications for 

 the internal organs. The number of these branches differs much in the 

 genera and families, but they are about the same from the several 

 spiracles. In the Mantodea they unite to a second, more internal, 

 common duct, and from which the branches for the internal organs 

 originate *. 



In all caterpillars, maggots, and in the larvae of the Hymenoptera 

 we observe only arterial vessels, the same in all the predaceous and 

 swimming beetles, and in the Heteromera and Tetramera. In all other 



o * 



* Marcel de Serres, Mem. du Museum, vol. iv. PI. XVI. f. 1. 



