66 



Nervous System of Insects. 



the last three abdominal, when there are in all thirteen (Fig. 

 i8). In the pupa, the last two of the thorax, and the first 

 two abdominal, unite into the twin-like post- thoracic (Fig. 

 i6), which supplies the meso, and meta-thoracic legs, and 

 both pairs of wings with nerves. The fourth and fifth 

 ganglia also unite, so that the adult worker-bee has nine 



Fig. i8. 



Nereoul Sysf.-m of Wor7ier Larra, aftey Vutican, 



ganglia in all. The brain, like our own, is inclosed in 

 membranes, is composed of white and gray matter, and 

 is undoubtedly the seat of intelligence. Hence, as we 

 should suppose, the brain of the worker is much larger 

 than that either of the drone or queen. The ganglia 

 along the cord are the seat of reflex acts the same as 

 is the gray matter of our own sjainal cord. Indeed, the 

 beheaded bee uses its members much more naturally than 

 do the higher animals after they have lost their heads. 

 This may arise from their more simple organism, or 

 from a higher development of the ganglia in question. 



The organs of circulation in insects are quite insignifi- 

 cant. The heart (Fig. 19, //) is a long tube situated along 

 the back, to which it is held by large muscles (Fig. ly, w), 



