THE GRAPE PHYLLOXERA IN CALIFORNIA. 83 



were not hard and straight and parallel to the sides of the body, but 

 bulged out and appeared rolled up and were soft, also sometimes con- 

 taining the sensory organs peculiar to the wing of the winged forms ; 

 (3) there were no wing muscles in the interior of the thorax ; and (4) 

 the structure of the vaginal segment of the abdomen was more devel- 

 oj^ed than in the mnnph. From this it appeared that this type of 

 nymphical was more comparable to the winged insect notwithstand- 

 ing its superficial resemblance to the nymph, and this conclusion 

 would be the more obvious when it is considered that the nymphical 

 is an adult insect of the fifth stage. 



In Italy the intermediates are said to be quite abundant among the 

 nymphs in the season of the year (July to October) when the latter 

 are being produced on the vines. They were found to be especially 

 abundant on vines of the American type but also not uncommon on 

 viniferae. 



In California, in the year (1915) in which were carried on re- 

 searches upon the intermediate forms, there was a very small avail- 

 able supply of infested American vines, and the observations were 

 confined chiefly to viniferse. On the American vines such as were 

 examined one nymphical was found. 



In looking over a series of slides made in 1914, a single nymphical 

 was recognized ; the year following, during the nj^mphal season (June 

 to November), frequent examinations were made on vinifera vines, 

 and in all 15 intermediates were secured from these. The individual 

 from the American vine (Wyoming Eed) and nine of those on vinif- 

 erse were recognized through the medium of mounting large numbers 

 of insects and later examining them through the microscope. The 

 remaining six were discovered on the roots through the use of a 

 binocular microscope, and all of them had rudimentary wing pads, so 

 that it is likely that others of the type lacking these pads were ob- 

 served but not recognized as intermediates. 



In the two years covering the investigation a total of 17 inter- 

 mediates came under observation. None of these was found earlier 

 in the year than the middle of September, and 12 were collected or 

 observed between September 14 and 27, 1915, and 1 on September 10, 

 1914. Of the 4 remaining, 1 was observed on a piece of root October 

 14, 1915, and 3 others October 27, 1915, 1 of which was in the fourth 

 stage and matured November 1. These 17 individuals differed 

 greatly one from another and represented all the types discussed by 

 Grassi and Foa. The types intergrade, and, in fact, no two of the 

 examples were alike. For the sake of comparison, they may be 

 divided into three arbitrary groups: (1) Those without vestige of 

 wing pads; (2) those with small buttonlike wing pads not visible 

 from above; (3) those with larger wing pads protruding (as in the 

 nymphs, fig. 9) beyond the lateral margin of the body and there- 



