IN August, 1873, the subject of phylloxera was first discussed in Sonoma. While it was generally known, for a few years previous to this time, that the vines in some localities were "sick," yet the true cause of the decay was unknown; and it was not until a year later that the Sonoma Vinicultural Club proved, beyond a doubt, that the dreaded phylloxera had already a strong foothold on this coast.

Various theories were immediately proposed regarding the manner and time of their introduction, but none up to the present time can be relied upon with certainty. European vines were introduced in 1860 and 1862, and without doubt a portion of the trouble may be traced to these importations. The native vines shipped from the Mississippi Valley may likewise have been infested. The exact manner of their introduction still remains a mystery. Still more mysterious, however, is the non-appearance of the form which increased the rapidity of the spread in France and other European countries, and makes the pest far more destructive than we find it in this State. With the assistance of the winged form, a distance of a few miles between districts offers apparently no barrier to their progress. Not only was this form necessary to the rapid spread of the insect, but has long been considered a necessary stage in the complete cycle of its life history. This most dreaded form, found in all other countries, has escaped the closest search upon the part of California vineyardists until recently, and its appearance at so late a date, leaves a doubt as to whether it may not, at any time, develop into all forms common to the insect, and be as destructive to our vineyards as to those in France.

In order that we may understand more clearly the position which this new form holds in the life history of the fully developed insect, a short sketch of its changes, during metamorphosis, will be necessary.

The French recognize four distinct forms, as will be noticed in the following synopsis: Beginning with the form as it exists in winter, we will find a small, dormant, dark brown aphis, somewhat flattened, having no wings, and quite unlike the usual mother of the summer season. With approaching spring, this insect becomes active, and either ascends to the upper part of the vine and becomes the gall insect, or descends to the roots and forms the root type, either direction of movement depending upon the surrounding atmospheric conditions.

The gall insect is not found in California, and therefore does not interest us. It is the insect which descends to the roots that will finally produce the winged form. After passing through three changes, or sheddings of the skin, the mother insect is developed. Several generations will thus be produced during the summer, and the increase will continue until the last mother louse dies, in the early part of winter; the younger insects are destined to become hibernants. If instead of three changes the insect passes through five, another form, called the pupa, is the result. This is the first indication of the winged form, and is easily distinguished by the small black pads on each side of its back; these contain the infolding rudimentary wings. The next change produces the fully developed winged form, which presents, with its beautifully colored body and four delicate wings, a striking contrast to the dull appearance of the winter form. The winged form lays the eggs for the development of the true sexual individuals, which are again wingless, destitute of suckers and digestive organs, and seem to have but one mission in life-to produce the winter egg for the rejuvenation of species in the following sum

mer.

It must not be understood that the insect passes through just three or five changes, or moltings, but this seems to be the average number under ordinary circumstances. The

different number of changes produce two cycles of life-one incomplete-which the insect may pass through during a single summer. In California, the incomplete cycle is probably the prevailing one, and it would appear that they can go on indefinitely without developing further than the three changes which produce the mother form. The production of the sexual individuals seems unnecessary. With the two different cycles there arise two different forms, larvæ and eggs, which may pass the winter in a dormant state. The eggs, in a warm country like the southern part of France, are frequently hatched at the beginning of winter, into a form of insect similar, if not identical, to the hibernating form of the mother louse; more frequently, however, they are not hatched until spring. Here, then, at the beginning of spring, the forms from both cycles are the same. It may be well to notice that in California no winter eggs, and only comparatively few winged insects, have been found.

A very peculiar phase in the development of the incomplete cycle was noticed by Balbiani while observing the Phylloxera quercus, a species closely allied to Phylloxera vastatrix, or grape phylloxera. He has since observed the same change to take place among the grape phylloxera. It had long been held that the last stages of the winged form of P. vastatrix alone produced true sexual individuals. By Balbiani's observations it was clearly shown that during the latter part of the season the wingless form sometimes performs the same function as the winged form in producing the sexual individuals. This offers an excellent explanation for the continued prolificacy, for so many years, of the Californian phylloxera without the intervention of the winged form. The number of eggs laid are the same in either case, their characteristics are similar, and both forms end in the production of a single win

ter egg.

In 1879 Dr. Hyde of Santa Rosa first succeeded in producing the winged form in this State, from root samples taken from Sonoma district. Seven insects were devel

oped into the complete winged form, showing clearly that, under proper conditions, our phylloxera would pass through that stage, which up to this time seemed to be missing. But strangely enough, they were all, or nearly all, of the infertile variety-a variety not abundantly found in European vineyards.

Since the above were developed, I believe none have been positively identified until last summer (1882) when they were found in very small numbers, in the pupa form, on the roots; and in one case a fully developed one on the vine itself. In only one or two cases was the winged form developed during the summer in bottles. Apparently, when all conditions are favorable they develop abundantly; for, while making some observations at the State University, I have taken at least fifty insects, in the pupa state, from a single small bottle. Soon after removing them, they developed into mature winged insects. All the insects, as far as noticed, were fertile; and very soon after they obtained their wings, each laid a solitary egg, and died. They were taken from the bottle one day, and in less than twenty-four hours some of the eggs were laid. Each of these insects should have laid from six to eight eggs, judging from the number laid by the corresponding form in France; but the conditions under which they were placed were so unfavorable, that no doubt their lives were much shortened by the treatment. However, they have been frequently kept some time on a plate of glass without apparently suffering from the change from the roots.

The exact time required in passing from the pupa state to the laying of the egg is uncertain; but it is presumably small, as the winged insects were removed from the "trap" as soon as discovered. They were supposed to have been entrapped by the moisture on the inside of the bottle soon after they became winged; and if this be so, the life of the winged insect must be short indeed.

I have said that there seemed to be "special conditions" necessary for their development. I was led to believe this from the

fact that out of twenty-five bottled specimens of roots, only two had the slightest indications of developing this form; and of these two, upon one was found the partly developed form as soon as the root was taken from the vineyard. As the specimens were taken from all parts of the vineyard, it is quite natural to conclude that only one or two vines had the special conditions necessary. A thick bunch of young, tender, fibrous roots produce the form in greatest abundance. The first supposition is again supported by the fact that the form has been found in the vineyards in only four different places, and upon about as many different vines. A single vine will produce this form, while none will be found on the surrounding vines. Diligent search was made last summer for this variety on a large number of vines, while looking for the common form of the insect, with results as stated above.

The pupa are found near the surface of the ground, and also to a depth of five or six inches. It is still doubtful whether they become fully developed winged insects before leaving the roots; but as the form has never been found on the roots, it is presumable that the transformation does not take place until they come to the surface of the ground. This may account for the unusual activity of the pupa, for their existence in this form, at best, is short; so their upward movements must be as rapid as possible.

At the time I took the winged specimen from the trunk of the vine, I also bottled an active pupa, taken three to four inches below the surface of the ground. In less than twenty-four hours this also became a winged insect. Possibly the removing hastened the development; if not, it shows that their rate of locomotion is quite rapid, considering the obstacles they meet in the way of hard soil and other impediments.

Keeping in mind the small number of places in which the winged form has been found, we may consider the vineyards as nearly exempt from this form, although there are spots which seem to show, by the more rapid spread, its existence in appreciable numbers. But such examples have

been very few; and many cases of rapid spreading have been attributed to this form because they could be accounted for in no other manner. Yet the sudden decaying of several acres of vines, all possibly infested from the same spot, and on the leeward side of the decaying district, forces the conclusion that the infection must be carried by the winds, and if so, the winged form must have prevailed to a considerable extent. There are notable cases in which narrow strips, extending in the direction of the prevailing winds, have become infested and completely and rapidly destroyed, while adjoining portions of the vineyard remained untouched. In other cases, the whole vineyard seems to collapse in the course of one or two years. Happily, these cases of such rapid destruction are few, and are the exceptions rather than the general rule. If the winged form prevailed in all the vineyards, the spread would be more sweeping, leaving fewer vines in a healthy condition, as we now find them.

Probably the most peculiar phase of the insect's workings is shown in some of the vineyards of Napa County. In these places the manner of spreading is entirely different from any thus far noticed; and if a typical spread by the winged form is possible, and is to be found anywhere in California, it would seem that it is developing here. No other vineyards of the State have the appearance of being similiarly infested. Several vineyards are included in the group. In two notable cases only two or three vines in a group have the characteristic short growth. Surrounding these spots are from one to two acres, dotted here and there with single infested vines. The only indication of disease was a slight change in color; otherwise, the foliage and fruitage was fully equal to that of any other part of the vineyard. It seems impossible that the vines could have become infested in any other way than by the winged form. The sickly vines were scattered in all directions from the original spot, mainly toward the valley; cultivation could not have distributed the pest so impartially; moreover, they were all in the same stage of

decay.

Both vineyards were affected in precisely the same manner, and had the same appearance throughout. It is also a notable fact that surrounding vineyards were more or less similarly dotted with yellow vines, significant of phylloxera, although no original source could be located as a starting point. Vineyards two years old were affected equally with older ones. In several acres of a twoyear-old vineyard single vines could be "spotted" as infested. Cultivation in so young a vineyard could scarcely have brought the pest from a distance. The choice, then, lies between infested cuttings and winged form.

The greater ease with which the winged form is found of late, and the peculiar phase of its movements, naturally suggests the question, Is not the original form developing into the more dreaded winged form? and may not the insect, in time, accommodate itself to the surrounding circumstances, and develop winged form as readily as in its native country? I believe when the insect was first discovered in California no instances of rapid, sweeping spread are recorded. The spread was slow in all directions. Each separate locality where the root insect is found shows that several years have passed since their introduction. Among these are the two districts in the eastern extremity of the infested part of the State. There has been sufficient time since they became infested to enable the pest to nearly destroy the original vineyards. In one case, where French vines were freely imported, the vineyard has been almost entirely uprooted, with the exception of occasional solitary vines, which still remain, showing too plainly, with their scanty growth, the cause of their decay. Slow but very destructive inroads are being made into the immediately surrounding vineyards. Still no signs of rapid spreading are visible, The other case spoken of is represented by a single vineyard nearly destroyed, while all the surrounding vineyards are in a healthy condition. Traveling westward through several districts, one or more vineyards in each will be found to contain well-developed spots,

yet no signs of rapid spread. In the older and more noted phylloxera districts, instances of rapid spreading are becoming more numerous, and anomalous cases are occurring more frequently, indicating a possible development of the new form.

In studying the different phases in which this insect is found, one cannot but notice the striking changes which may be produced by accustoming the insect to varying conditions. The gall louse may be entirely driven from a vineyard by replacing the vines with other varieties; the common root form may, after several generations, be persuaded to live above ground upon the leaves, without assuming the characteristics of the gall louse; surrounding circumstances will, too, determine the length of the life cycles. If the changes can be produced artificially, is there not a possibility of the different forms being reproduced in the open field?

In order to compare the rapidity of production of the winged form of California with that of other countries, I would note what Professor Riley says of their production in the Mississippi Valley, and compare it with the numbers found in California. He says: "An ordinary quart preserve jar filled with such roots (rootlets from vines in proper season), and tightly closed, will furnish daily, for two weeks, a dozen or more of the winged females." If every vine in a vineyard bears the winged form at this rate, it is easy to form an opinion of the vast numbers that would thus be produced, and to see the ease with which they could be carried into the air.

Observation has not yet shown that California produces vineyards in which all the vines are infested with winged form, but rather that the vines thus affected are very few indeed. If this be the case, vineyards at a distance are not apt to become infested by the blowing of the form, for the number which could be taken into the air must be exceedingly few, and the possibility that any one of these will ever find suitable condition for future action in a distant vineyard is almost beyond calculation.

F. W. Morse.