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- 
oped than in the nymph. 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 viniferae. 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 nymphal 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 Red) and nine of those on vinif- 
erae 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- 
