fornia. Mr. Koebele claims to have sent in some 40,000 specimens in from 40 to 60 species, most of them listed by him under the title of "Insects Feeding upon Coccids." Omitting Vedalia cardinalis and Novius kæbelei feeding upon Icerya, which stand by themselves, about half a dozen species out of from 40 to 60 gained a footing worthy of attention in California: Orcus australasia, O. chalybeus, Rhizobius ventralis, R. debilis, Cryptolemus montrouzeri, and perhaps Leis conformis. To these may be added Rhizobius lophantæ, also described as R. towoomba, which gained a foothold by an accidental introduction many years ago. Of these, Orcus australasia has died out altogether. Orcus chalybeus barely sustains itself in a single restricted locality in Los Angeles county. Leis conformis seems to have died out, or at least has not increased. Rhizobius ventralis has firmly established itself in Santa Barbara and Ventura counties, and occurs annually in goodly numbers, but it seems unable to thrive elsewhere as yet. There is some evidence, however, that near the coast, in Los Angeles county, it will eventually make itself at home. R. debilis, of which Mr. Koebele says, "next to R. ventralis Er., the most numerous of all the Rhizobiids, and will prove one of the best acquisitions we could get," is so rare in 1896 that I have not been able to get hold of a single specimen. In the very orchards where it was said to occur in extravagant numbers, not a specimen could be found, and not one of the colonies introduced into New Jersey, which it was intended should consist of this species chiefly, contained even a single specimen. R. lophanto was accidentally introduced many years ago, and is well spread all over southern and central California. It is rarely abundant, however, and prefers woods and cañons to orchards. It is not a factor of any importance as against scale insects. Concerning the Cryptolomus, I can say little. It seems to do well in confinement, but I have not seen anything of it in the open. At Berkeley, where some specimens were colonized on plants infested by mealy bugs, the beetles are said to have died out, while it is certain the mealy bug has not.

The whole practical effect, then, of Mr. Koebele's scouring "New Zealand, Australia and adjacent islands," has been the introduction into California of a single species, which, after four years, has established itself in two counties, in which black scales are yet abundant. I will go further and say that there is no reliable scientific evidence that any reduction of black scale, even in these counties, is not due

to causes other than the Rhizobius. It is certain that the possible fifteen thousand million (15,000,000,000) descendants of a single pair of R. ventralis have not, even on Mr. Cooper's ranch, exterminated the possible one thousand (1,000) descendants of a single black scale. * Mr. Koebele's statements as to the possibilities for predaceous species, are made without regard to the fact that such things as natural limitations exist; that geologic conditions may prove a bar for predaceous species which would not check the form they normally feed upon, and that this "simple matter" which he solves so easily, really demands a modification of nature's laws to suit the farmer. Our past attempts in this direction have not given us much hope for the future.

There remains the possibility of a "fluke." It is not inconceivable that a predatory species or a parasite, introduced without its enemies from a country in which natural conditions are against it, into a new country in which the conditions are more favorable, may increase abundantly and flourish on some native or introduced injurious species. In such a case the injurious form might be very much reduced and rendered harmless; but the predaceous species would have to become correspondingly scarce or put on new food habits, and this would give its original prey a chance to recover. A good "fluke” is equal to a success, and in the hope that some such fortunate occurrence may result, it will be my effort to introduce into New Jersey as many Coccid-feeding lady-birds from all sources as offer any possibility of surviving in our climate.

DISEASE CHECKS.

A better hope offers in another direction. While nature does not favor the farmer, and does not allow one of her productions to work out the absolute destruction of any other, she does not, on the other hand, favor the too rapid increase of any form, and disease is brought in to check one inclined to break bounds. Placed in favorable climatic conditions, the San José scale for some years bred and multiplied exceedingly. Signs are not wanting now that this exceeding prosperity may result in decreased vitality. It is certain that in Cali

*I am using Professor Woodworth's figures here. The black scale often contains two or even three thousand eggs, but Professor Woodworth considers one thousand a fair average under ordinary conditions. In any case there is only one annual brood.

fornia many of the insects die without reproducing. It is certain also that the young are not so numerous, and the larvæ are not nearly so active as they are in New Jersey, which became more lately infested. In California almost every infested twig shows diseased scales, but the fungus bred from them may not have been the original cause of death.

Professor Rolfs informs me that disease has attacked the scale in Florida, and Dr. Howard gives it as Mr. Marlatt's observation in Maryland, that the larvæ seem to show a lack of vitality similar to that observed by me in California. In New Jersey nothing of the kind has been observed as yet, but this feature of the case will not be left out of consideration in future experiments.

NATURAL ENEMIES OF THE SAN JOSÉ SCALE.

According to Howard and Marlatt, three, and possibly four, species of parasites have been bred from the San José scale. These are Aphelinus fuscipennis How., A. mytilaspidis Le Baron, Aspidiotiphagus citrinus Craw, and Anaphes gracilis How. All of these are also feeders on other scale insects, and as to the latter it is possible that it may not have been bred from the San José scale, but from an overlooked specimen of the common oyster-shell bark louse. Aspidiotiphagus citrinus, first described from California, has been bred in the East only in Florida. Aphelinus fuscipennis in the East first bred by me in New Jersey, has since been found infesting the scale in Virginia, and is a common enemy to it in California. It is by all odds the most abundant of the species, and the work done by the others is very subordinate. While every specimen feeding on it in ever so slight a degree aids in the control of the scale, yet in themselves these species are not of great importance.

APHELINUS FUSCIPENNIS Howard.

This little insect belongs to the family Chalcidida, and is a common parasite of armored scales. It occurs all over the country in greater or less abundance, and is as much a native of the Atlantic as it is of the Pacific Coast. It is very minute, hardly as long as an ordinary

San José scale is in diameter, and is of a somewhat straw-yellow color. The eyes are dark, and as they contrast in color, appear rather prominent. The antennæ, or feelers, are rather short, a little thickened at the tip, and are kept in constant motion while the insect is moving among the scales. The wings are ordinarily laid flat upon the back, and when the little creature is seen on an infested tree, it will be found walking or hopping, rather than flying over the scales, and testing them with its antennæ, seeking a suitable one in which to lay an egg. In California it is easy to find specimens on any infested tree at any time during the year. In New Jersey they are much more rare, and in many places the trees do not show the slightest signs of the presence of the parasite. A single egg is laid in each scale, and the parasitic larva feeds upon the insect underneath, checking reproduction and ultimately destroying it. When ready to emerge, the parasite cuts a small, round hole in the scale, through which it makes its exit into the open air. It is easy, therefore, to determine the part that has been played by this insect in lessening the number of scales, and there is no sort of doubt that in California it is extremely effective, particularly in the southern portions of the State. There it breeds during the entire year, specimens having been found in January and February, as well as during all the summer months. This gives it opportunities that are lacking in New Jersey, for from December until April the insect hibernates in our State, and a large proportion of the specimens are winter-killed. The species therefore begins its work on the scales in spring in small numbers only, and its rate of reproduction does not begin to compare with that of the scale; hence by the time the parasite has increased so that it might become beneficial, winter again sets in, and the spring following the same story is repeated. This is a marked example of the effectiveness of a parasite in one locality and of its absolute inefficiency in another.

The figure herewith given illustrates a closely allied species belonging to the same genus, and will serve to give a fair idea of the general habitus of the scale parasites. It is probable that eventually all the parasites of the oyster-shell bark-louse and of the scurfy scale in our State will also attack the San José scale; but our species are used to dealing with forms having only one or, at most, two broods in the course of the year, while the pernicious form breeds continuously for months, and is therefore in a position to outrun enemies that control our ordinary species with little difficulty. The following is quoted

from Howard and Marlatt as to the work of this species in California: "Aphelinus fuscipennis is undoubtedly a very efficient aid in keeping the San José scale in check. Mr. Alexander Craw, in the Report of the State Board of Horticulture of California for 1891, states that he found it doing such effective work in an orchard in the neighborhood of Los Angeles that complete extermination of the scale was confidently looked for. It was afterwards learned, however, that the orchard became re-infested, and also that the partial exter

Fig. 8.

Aphelinus diaspidis Howard. (From Division of Entomology, U. S. Dep't Agriculture.)

mination of the scale in this instance was, in a measure, seemingly due to a fungous disease." This illustrates the fact that even in California reliance upon this species alone is ill-placed.

LADY-BIRDS.

The most effective enemies of scale insects and plant lice are to be found among the lady-birds or Coccinellida. These are comparatively small; sometimes even very small, beetles varying from an almost round to an oval outline, always somewhat flattened beneath and distinctly or very strongly convex above. Taken as a whole, lady-birds are predaceous insects; there are, however, some exceptions, and a few species feed upon plant tissue exclusively. Quite a number of others vary their diet by feeding upon pollen, sometimes in considerable numbers, and many of them have been observed feeding upon fungi.