I am twelve years old. I have a canary, and my brother and I had a pair of squirrels, but one died.

HORACE C. FOOTE, 109 East Fifty-seventh Street, New York City.

I have a collection of stamps, and would gladly exchange with any correspondents. I have stamps from Colombia, Venezuela, Germany, England, and other countries.

ELIAS DESOLA, 162 East Sixtieth Street, New York City.

I would like to exchange flower seeds with any little girl in California or Florida. I have verbenas, mixed phlox, four-o'clocks, sweet-williams, balsams, alyssum, salvia, mignonette, and red and white petunias.

ADA BELT, 1099 Wilson Avenue, Cleveland, Ohio.

I have a collection of postmarks, and would like to exchange with any correspondents of this nice paper. I am eleven years old.

"EXCHANGE," 939 Main Street, Buffalo, Erie County, New York.

If any correspondents will send me a list of the stamps they require, and also of those they have to spare, I will like to exchange with them.

JOHN R. BEDFORD, 5 Spencer Place, Fourth Street, New York City.

I would like to exchange some revenue stamps for postage stamps.

Among those I wish to exchange are two varieties of one-dollar stamps and a forty-cent stamp.

LEONARD T. BEECHER, Wellsville, Alleghany County, New York.

I take YOUNG PEOPLE, and I think it is splendid.

I have a great many French, Italian, English, and German postage stamps which I would like to exchange for others.

GEORGE B. DONNELLY, P. O. Box 4574, New York City.

I am collecting postage stamps, and would like to exchange.

Correspondents will please state the number of stamps in their collection, and send me their list. I have twelve hundred stamps, and I am thirteen years old. I would like to know the age of my correspondents.

CHARLES S. PETRASCH, 13 West Thirty-second Street, New York City.

I would like to exchange postmarks with any boy readers of YOUNG PEOPLE in the West. I am twelve years old.

ARTHUR S. MOORE, 40 Third Place, Brooklyn, New York.

I would like to exchange postage stamps with any correspondent.

R. L. PRESTON, P. O. Box 327, Lynchburg, Virginia.

LOUISE.--Your question, "Is the mosquito of any use in the great economy of nature?" has often been asked by many older and wiser than you, for it is not generally known that in their larval state mosquitoes form an important branch of nature's army of tiny scavengers. The larvae live in the water of stagnant pools and marshes, and feed upon particles of decaying matter, and as their number is so very large, the amount they devour is considerable. By thus purifying the water they destroy the miasma which would otherwise arise and pollute the atmosphere to such an extent that no human being could breathe it with safety. The value of the work accomplished in tropical countries by these tiny scavengers is very great. It is estimated that the air of certain marshy regions would be so poisonous that no animal higher than a reptile could breathe it and live, were their purifying influence removed. We do not know that mosquitoes in the winged state have any useful mission beyond that of depositing the eggs which produce the larvae, but that alone saves them from being "nothing but a nuisance."

F. A. REILLY.--The subscription price for HARPER'S YOUNG PEOPLE for 1881 will remain one dollar and fifty cents, the same low figure as for the first volume.

BRIAN B.--The large green worm that feeds on carrot, caraway, parsley, and some other common garden plants is the caterpillar of the _Papilio asterias_, a large black b.u.t.terfly which is seen in great numbers at midsummer, hovering about the flowers in gardens. It is especially fond of the sweet-scented phlox. This b.u.t.terfly is very handsomely marked with rows of yellow spots near the margin of its wings, and on the hind wings, which are tailed, there is also a row of blue spots, and near the lower angle an orange-colored eye with a black dot in the centre. The wings of this handsome insect expand from three to four inches.

"THISTLE."--It is not easy to say why such great numbers of potato-bugs are found crawling on the sea-beaches. These striped cantharides are so numerous in all parts of the country that they are probably blown seaward by the wind, and naturally sail ash.o.r.e on the tide.

You will find simple directions for pressing flowers and leaves in the Post-office Boxes of YOUNG PEOPLE Nos. 34 and 46.

F. B. W.--Write again to your correspondent. There are so many possible reasons why he has not answered you that it would not be fair to him to print your notice. Possibly he has misdirected the letter to you.

Favors are acknowledged from Fred P. Herron, Albert C. B., Jessie R.

Ellerby, E. N., Richard F. Morgan, Willie C. Chapman, S. B., Frank Davis, S. Donald Newton, Gertrude B. Duffee, Frank Haid, John R.

Bancroft, H. S. G.

Correct answers to puzzles are received from Eddie S. Hequembourg, Mary Tiddy, "Chiquot," William H. Dobson, Dana D. Stanton, "Milwaukee," Percy McGeorge, "Nellie Bly," E. D. W. R. Garden, George Volckhausen, James H.

Beddow, Howard A. Esterly, "Ivanhoe."

John H. Bartlett, A. O., and J. C. Locher have sent neat specimens of the five-pointed star, which were received too late for acknowledgment with the others.