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transported long distances and to establish themselves in new districts which furnish sufficient humidity coincident with food-supply during any considerable portion of the year.

CAPACITY FOR DAMAGE

The capacity of the weevil for damage to the cotton crop is not so great in the Peruvian coast region as it would be in a tropical region that is truly humid throughout the year. But its damage varies considerably within this region, according to a variety of factors. Other things being equal, its damage in the various districts is directly proportionate to the annual duration of sufficient relative humidity to maintain its activity. It does the most damage in those districts where the bulk of the squares are formed during the most humid season of the year, providing that the temperature is sufficiently high during that season to accelerate rather than retard its development. From these facts it is evident that the damage is high in Piura, and probably still higher in the central coast region of Peru. Its average damage for the whole coast region must be considerably less than that of the boll-weevil in the more humid region of the southern United States, but it can hardly fall below 20 per cent. This means an annual loss to Peru from the weevil of about £400,000.

WORK FOR THE FUTURE

Future work should consist of fostering the parasites of the weevil so far as practicable in the different districts; introducing and estab lishing one or both of the two species of ants above mentioned, Solenop sis geminata and Ectatomma tuberculatum, for attacking the early stages and adults of the weevil respectively, first ascertaining whether these two species are incompatible with each other or whether they may be maintained side by side in harmony, in the former case selecting the more effective of the two; and working out the details of the cultural control measures already outlined.

In order to carry these lines of work through intelligently, full data are needed on humidity and temperature ranges of the weevil and its enemies; and on both cotton varieties and cultural and irrigation methods adapted to the soils and climatic conditions of the different districts in the coast region. Such data can only be obtained by executing well-planned series of experiments in the laboratory and insectary in intimate connection with control work in the field.

UNSPOTTED TENTIFORM LEAF MINER OF THE APPLE

(Ornix geminatella Pack.)

By LEONARD HASEMAN, Department of Entomology, University of Missouri

The unspotted tentiform leaf miner of the apple has been exceedingly abundant for the past two or three years throughout the apple sections of Missouri. It has been gradually increasing in numbers for three or four years and probably reached a climax the past summer in this vicinity. In the orchard here on the horticultural grounds it has been so abundant that during the months of September and October it was almost impossible to find a single full grown apple leaf which did not have from one to twenty mines. Fortunately this type of leaf miner becomes most numerous from the middle to the latter part of the summer and therefore is not as destructive as it would be should its heavy work come earlier in the season.

The unspotted tentiform leaf miner has been known to science for many years, having been first imperfectly described by Packard in his "Guide to the Study of Insects" in 1869. Since that time a number of other names have seemingly been applied to the same species where it has been bred from the foliage of trees other than apple.

Life Cycle-For the past two years the writer has been studying this pest in its relation to horticulture in Missouri. In this study a number of interesting points have been determined with reference to its life cycle and habits. The pest in this vicinity invariably passes the winter in the pupal stage protected by a rather firm cocoon which is made somewhere along the edge of a leaf late in the fall. After the first heavy frosts come the leaves containing the cocoons and pupa fall to the ground where they remain throughout the winter.

The past spring the first moths began to emerge in the insectary on April 17 and on May 3 they were fairly abundant in the orchard. From early May until late November either the adults or the caterpillars in the mines were found abundant here in the orchards. The life cycle is completed in from four to five weeks and five fairly distinct broods were made out in this latitude the past summer. The first brood completed its cycle early in June and about the same date each month following until October succeeding broods were to be found. The broods overlap considerably so that the pest does not have sharply defined generations but the periods at which the first appearance of the heavy attack of succeeding generations is noted. may be rather sharply made out.

The parent moths are never very active though after they have emerged a day or two they are seen to fly about in breeding cages and in the orchard during the evening. When at rest the moth takes the characteristic position of other closely related moths, namely, standing with the tip of the wings and the end of the abdomen touching the object on which it rests and with the front part of the body propped up on the two front pairs of legs at an angle of 45°.

The eggs seem to be deposited during the evening and night and are placed singly on the lower side of the leaves. The egg is slightly oval in outline and exceedingly small, from .25 mm. to .4 mm. in length. The shell is beautifully sculptured both on the upper and lower side. This sculpturing is uniform over the entire surface and is so delicate that it requires very high magnification to bring it out. The sculp turing on the lower half of the shell is partially obliterated by the cementing substance which attaches it to the leaf. The writer has not succeeded in locating fresh eggs but from the appearance of the freshly hatched eggs, they seem to be quite flat.

Upon hatching the young caterpillar bores at once beneath the epidermis of the leaf. Not infrequently this tunnel is made through the lower shell of the egg.

For the first few days the caterpillar produces a serpentine type of mine which, to begin with, is not readily distinguished. After three or four days the caterpillar ceases to advance farther under the epidermis of the leaf and begins to eat out the cells on either side of the narrow serpentine mine, thereby producing a distinct blotch mine, and in three to four days more the blotch mine begins to take on the tentiform shape due to the drying out of the lower side of the leaf and to the tension produced by silk spun inside the mine by the caterpillar. The larva, therefore, in its development begins with a serpentine mine and ends with the characteristic elevated tent iform. mine. After the tentiform mine is once produced the caterpillar feeds for a number of days upon the layer of chlorophyll cells immedi ately under the upper epidermis which causes the mine to take on a more or less transparent appearance when all of the chlorophyll has been removed. The mine is completed in from eight to fourteen days. The young caterpillar leaves a trail of fine excrement along the course of the serpentine mine and scatters it promiscuously throughout the blotch mine but in the tentiform mine it is largely collected in one end and may be partly covered with silk.

After the mine has been completed the caterpillar usually continues to inhabit it for a few days after which a small round hole is eaten through the lower side of the mine and the larva crawls about on the foliage and on the limbs of the trees in search of a suitable place to

pupate. Not infrequently it has been found to fold over the edge of the leaf and feed to a slight extent in a new place, though such cases are rare. The caterpillar on preparing to pupate draws over a portion of the edge of a leaf or folds over the edges at the tip of the leaf by means of silk threads and after lining this with silk it pupates, coming out a week to ten days later as the moth. It is interesting to watch the caterpillar tugging away at the silk threads as they are being attached and to see it tie these into bundles so as to shorten them and thereby draw down the edge of the leaf. There would seem to be quite a period between the appearance of the moths and the time at which the first eggs are deposited.

In the development of the caterpillar it passes through four larval stages. In the first stage it is footless, snow white except for a slight tinge of yellow on the head, and somewhat resembling a minute flatheaded borer. In this stage the larva makes the serpentine mine and in it changes to the second larval stage. This is also footless and white except for the head which becomes brownish and the first thoracic segment begins to take on a dorsal black blotch. While in this stage the mine is transformed into a blotch mine. With the change to the third larval stage, which occurs in the blotch mine, the head becomes darker, the thoracic blotch begins to take on the appearance of four irregular blotches and the six thoracic and eight abdominal legs appear. In this stage the larva increases in size rapidly and the body becomes darker. It is usually during this stage that the blotch mine is transformed into the characteristic tentiform mine. The change to the fourth larval stage takes place in the tentiform mine and usually before much of the chlorophyll layer of cells is consumed. In this stage the caterpillar has a brownish head with four dorsal black spots and four similar ones on the first thoracic segment and the body is dark grey with regular rows of white tubercles bearing prominent hairs. After feeding in the mine until mature the larva leaves it and prepares to pupate.

The unspotted tentiform leaf miner will probably never prove to be an exceedingly important pest of the orchard. One can hardly conceive of its ever becoming more abundant than it has been in the orchards of Missouri for the past two years and there is little sign of its having seriously injured either the trees or the apple crop the past summer. In case it does require special attention it can be checked by early spring plowing for the destruction of the leaves containing the wintering pupæ. Spraying has been carried on in the orchards here and has not had the least effect upon the development of the insect, due to the fact that the caterpillar is never ex

posed to the poison upon the foliage except in those cases where it may feed to a slight extent after leaving the old mine.

In connection with the study of the development and habits of the miner, the writer has had an opportunity of noting the effective work of parasites. During the summer and fall various hymenop terous parasites were exceedingly abundant, so numerous in fact that only a very small percentage of each brood of miners succeeded in maturing. The majority of the miners are killed by small parasites when the mine is yet in the blotch stage, while many more are destroyed by other species of parasites after the mine takes on the mature condition. With the help of these various species of parasites there will probably never be any occasion for fruit growers to fear this miner. The various species of parasites reared from the mines of this caterpillar are now being studied by Prof. C. R. Crosby.

A NOTE ON TWO ELM LEAF APHIDES 1

By EDITH M. PATCH

During the past few weeks several items concerning Elm leaf aphides which have come to my notice have interested me enough so that I venture to present them here, not as a formal paper, but merely to call attention to the fact that two perfectly distinct and easily distinguishable species causing elm leaf curl are present in the United States.

One of these migrates to Pyrus and Crataegus where it is known as the woolly aphid of the apple and that this species extends from the Atlantic to the Pacific coast nurserymen and apple growers almost everywhere can testify to their sorrow.

A second elm leaf species, which is present in California and elsewhere in the Pacific states, appears to be identical with a species recorded from England, Germany, Sweden, and elsewhere which has been ascertained by European workers to migrate from Ulmus to Ribe 8 and is at present known as ulmi (fodiens) of Europe.

These two species can readily be distinguished by their antennæ. The Ulmus-Ribes species is characterized both in the spring and fall migrants by having joints V and VI without annular sensoria and the terminal sensorium of V is circular and fringed; the terminal sensorium of VI though somewhat irregular in shape being also fringed. The Ulmus-Pyrus species has typically annular sensoria on both V and VI in the fall migrant and on V in the spring migrant, while in both forms the circular sensorium of V is lacking, the terminal sensorium being

Papers from the Maine Agricultural Experiment Station: Entomology No. 60.

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