l8gi.] ENTOMOLOGICAL NEWS. 27 



two large insects floundering about. I took them out, placed 

 them in an envelope, and hurried home, where I transferred them 

 to a bottle. They were two females of the Zeuzera, and when 

 dried made excellent specimens; antennae perfect, and markings 

 brighter than any of the males. I took and mounted during the 

 season 2000 specimens exclusive of diurnals. 



-o- 



ELEMENTARY ENTOMOLOGY-. 



Eighth Paper. INTERNAL ANATOMY (concluded). 



The nervous system consists of a series of paired nerve-knots, 

 or ganglia, connected by two nerve cords (commissures}, and 

 extending the entire length of the body. Typically, there is a 

 pair of ganglia to each segment of the body, but usually the num- 

 ber of pairs is less than the number of segments, owing to the 

 union of adjacent pairs. This nerve chain lies below (ventral to) 

 the alimentary canal for the greater part of the body, but in the 

 head, the two commissures pass upwards, one on each side of 

 the oesophagus to a mass of united ganglia lying on the dorsal 

 side of the canal in the head. This mass is the brain, or supra- 

 cesophagial ganglion; it is thought to be formed by the union of 

 several pairs of ganglia corresponding to the number of segments 

 of which the head is formed. 



From the ganglia of this nerve chain, nerves are given off to 

 surrounding organs. Certain other ganglia are connected with 

 this nerve chain which do not correspond in position to the seg- 

 ments. These latter ganglia supply by their branches the ali- 

 mentary canal and the tracheae. 



The organs of sight are the simple and the compound eyes.* 



* See ENTOMOLOGICAL NEWS, vol. i, p. 104. 



In 1888 and 1889, Prof. Felix Plateau published in French the results of his studies on 

 the vision of Arthropods. Dr. David Sharp, of London, gave an account of these ex- 

 periments in the " Transactions of the Entomological Society of London" for 1889, p. 397, 

 et seq., concluding with two " general impressions" which he has '' derived from the study 

 of Prof. Plateau's valuable experiments." 



1. " That insects in motion are largely guided by thedirection of light and the existence 

 of lights and shades " 



2. " That there is at present no evidence at all that the light-perceptions are sufficiently 

 complex to be entitled to be called seeing; but that, as the large development of the com- 

 pound eye permits the simultaneous perception of movement, its direction, and of lights 

 and shades over a certain area, a dragonfly may pursue and capture another insect without 

 seeing it in our sense of the word seeing. (Trans. 1. c. pp. 407, 408)." 



