202 



" Riley in his 8th Report, page 159, has described similar 

 tracheae in the Phylloxera as nerve chords. Is he right?" 

 On turning to Prof. Riley's Reports ^ I was not a little sur- 

 prised at the description of the nervous system. It seems to 

 me that it is not only not quite accurate for that insect, but 

 also that it hardly corresponds to the nervous system of any 

 animal. 



Although I have not studied the sexual individuals — 

 which are the ones described by Prof. Riley, — I have not the 

 least doubt that the objects very carefully drawn by him as 

 nerves are nothing other than the tracheae, as suspected by 

 Mr. Putnam. The nervous sj'stem will certainly be found to 

 present other peculiarities than those figured by Prof. Riley, 

 and probably will differ only slightly from the same system as 

 observed in the sexless individuals. 



Fig. 9 — Phylloxera vastatrix Planch. — radidcola, winged. 



An oblique view of the upper left surface of the central portion of the nervou^ 

 sj'stem, as seen after cutting away the dorsal wall of the body, and the oesophagus 

 where it ascends from the level of the brain-commissure. Magnified about 100 

 diameters. 



The following observations were all made on sexless root- 

 infesting individuals in the month of August 1876. The cen- 

 tral portion of the nervous system, in both winged and wing- 

 less forms, came under observation. The accompanying figure 

 represents the ganglia in a pupa of a winged form in which the 

 tip of the Aving-pads reached backward to near the middle of 

 the abdomen. 



1 Seventh annual report on the noxious, beneficial aud other insects of the state of 

 Missouri, . . . 1875, p. 99, fig. 19, and foot note. 



Eighth annual report on the noxious, beneficial and other insects of the state of 

 Missouri, . . . 1876, p. 158, fig. 48 b and e ; p. 159. 



Trans. St. Louis Acad. Sci., v. 3, p. 283, fig. 22; p. 284. 



