Phylloxera caryaevenae Fitch.
Pemphigus ? caryaevenae Fitch.
Phylloxera caryaevenae Riley.
The galls of this species we readily separated from those of any of the other species found upon Hicoria. They resemble more closely those of certain of the Cecidomyids occurring on different species of oaks and other plants.
They always form, either along the main rib or more frequently along the transverse veins, shorter or longer folds or plaits projecting more or less evenly from both sides, though usually more prominent above, where they form elongate ridges or carinae, which are often transversed by 3-5,, or more, short, elevated branches, about equal in length to the diameter of the gall. The opening or slit is always on the underside and, while fresh, is tightly closed except at the outer end, and covered by a delicate white or greenish pubescence which also more or less completely covers the entire surface beneath. The color is generally yellowish-green, though very frequently also brownish or purplish. Two or more are often confluent, so that their length varies from 6-14 mm or more, and their diameter from 2-3 mm.
The gall begins to form early in May. It occurs not only upon Hicoria tomentosa but upon several other species of Hicoria and is widely distributed over the eastern half of the United States, having been observed from New York to Florida, and west as far as Illinois and Missouri.
No winged migratory female has yet been observed, but the most remarkable fact is that I have been unable to discover in any of the many galls examined from 1880 to 1890 a sexual form, though examinations were made during different months. The only occupants thus far found in these galls were the true stem- mothers (of which 1-3 have been observed in the same gall) , their eggs and the wingless sexuparae in different stages of development.
By the middle of August, when the majority of the galls had become dry and empty, but a few remained still green and contained the still living, though much shrunken, stem-mother, a small number of eggs and a few larvae, but no migrants or sexual individuals.
On July 19, 1890, when many of the galls still contained their usual inhabitants, extended and careful search was made to discover the whereabouts of the larvae after leaving the galls. Small colonies, absolutely identical with those found within the galls, were finally discovered snugly hid away either in deep cracks of the bark or at the bottom of deep and more or less completely closed depressions, which are found on the trunk and stouter twigs and which are caused by the decay and dropping out of small branchlets. Here the insects live upon the juices from the tender bark which forms at the bottom of the cavities. These colonies usually consist of the stem-mother, a number of fully grown apterous females and larvae (both the direct progeny of the stem-mother) and eggs of three different sizes. The smallest, and most numerous of these eggs, correspond exactly in size and general appearance with those deposited by the stem- mother in the galls, while the others are about twice as large but yet of two sizes, the larger ones of a regularly ovoid shape, the smaller more conoidal in outline. The former produce, after a few days, the true sexual female, and the latter the male, which pair, when the female brings forth her single impregnated or winter egg which doubtless hibernates within the cavity.
In some of the depressions no stem-mother is found, but only the other forms here described and a few of the winter eggs.
During the summer of 1902 another effort was made by me to discover, if possible, the winged migrant of this species, though without avail. Unfortunately nearly all the trees on which the galls used to be plentiful had been cut down, leaving but a few small shrubs in that particular locality, with still fewer galls on some of the leaves. These galls were also extremely scarce on trees in the woods some distance to the north, in all of which the usual apterous forms and some eggs were present, though not a single one of the winged migrants. That this form, after a shorter or longer interval must exist, seems quite plain, while otherwise the species is doomed to become extinct, since the migration of some of the apterous forms from tree to tree, especially if such trees should grow at some distance from each other, must naturally be rather slow and uncertain. I take it, therefore, for granted that the spread of this species depends, as in other species, on a winged migrant, which sooner or later will be found.
