emergence from these pupa is given in Table XXXII. The data covering lots 1 to 6 show that the more mature pupa succumbed to immersion more quickly than the younger pupe of lots 7 to 12. Thus many of the young pupæ emerged as adults after being submerged 4, 5, and 6 days, while submergence for these periods killed nearly all the older pupæ. Submergence for at least 7 days is necessary to assure the death of all pupæ. BURIAL IN SOIL. Many entomologists have made statements regarding the efficacy of burying infested fruits in the soil as a method of destroying fruit flies. These references have been summarized by Severin, hence need not be considered at length here, particularly as they deal with a method that is decidedly unsatisfactory and seldom effective. Gurney found that pupæ buried 6, 8, and 12 inches below the surface of the soil produced adults that were able to escape. Severin found that adults could make their way to the surface from pupa buried 2, 3, and 4 feet beneath dry sand, and from pupæ buried 2 feet beneath wet sand, but that no adults escaped through 2, 3, or 4 feet of dry soil. Mally found that 10 inches of soil shoveled loosely over fruits did not prevent adults from escaping later, but that no adults could reach the surface through 10 inches of well-tamped soil. No adults escaped from 20 pupa placed in the center of a cake of mud one-half inch square taken from the heavy, tenacious soil of the vegetable gardens at Waikiki. The mud became thoroughly dry without cracks before the end of the normal pupa stage. A cake of the same soil 14 inches square, however, on drying developed a crack through which 50 adults made their escape from 75 pupa buried within the center of the square. While adults can not make their way through a foot of well-tamped soil, it is difficult to bury host fruits in such a manner that the soil covering will remain firm. The rapid decay and settling of fruit, if any amount be buried in the same excavation, cause cracks to develop through which adults can escape readily. While many fruit flies can be killed by proper burial, indifference and carelessness among workmen will always make possible the escape of many adults. BURNING AND BOILING HOST FRUITS. Burning or boiling host fruits is a sure method of destroying the immature stages of the Mediterranean fruit fly provided the work is feasible and can be done thoroughly. The usual practice of throwing fallen infested fruits into a compost pit and burning over them every few days such trash as may have accumulated is not a trustworthy method of destruction, inasmuch as the heat produced is very often insufficient to cook or burn the fruit thoroughly or to reach the pupa in the soil beneath the fruit. SUMMARY. The Mediterranean fruit fly (Ceratitis capitata) was discovered at Honolulu in the Hawaiian Islands in 1910. Since that time it has spread to all the islands of the Hawaiian group, and because of the equable climate and abundance of host fruits, has effected a serious and permanent check to horticultural pursuits, and put an end to all export trade in fruits except that in bananas and pineapples. Research seems to have fixed the native home of C. capitata in tropical Africa. Its spread has been slow but persistent throughout tropical and semitropical countries, until at the present time it is known to have become a pest in every continental area except that of North America. With the Mediterranean fruit fly now well established in Bermuda and the Hawaiian Islands, it would seem that it is only a matter of time before it will be inadvertently introduced and become established in California and the Southern States. The frequent interception and destruction of infested fruits from Hawaii at California ports, by officers of the Federal Horticultural Board, indicates the ease with which the introduction of the Mediterranean fruit fly might occur were Hawaiian fruit permitted unrestricted entry to the mainland of the United States. No edible fruit in Hawaii, except the pineapple, escapes attack. The banana, when in good condition, is never infested, infestation having been noted only when the fruits were overripe or injured. The Mediterranean fruit fly has been reared in Honolulu from 72 species of host fruits, including the peach, plum, pear, guava, mango, orange, lemon, grapefruit, banana, etc. A large proportion of the host fruits are inedible. Throughout the littoral regions a continuous cycle of host fruits is available for infestation throughout the year; hence there are no starvation periods for the fly to survive. With such a quantity and variety of host fruits, nuts, and vegetables in which to propagate, and enjoying an ideal climate, the mean temperatures of which vary between 68° and 79° F. for the regions in which the fly is a most serious pest, the Mediterranean fruit fly finds no check to its rapid increase. While a single generation may require as few as 17 days during the warmest weather, there are usually 15 to 16 generations a year at Honolulu, and 10 to 12 generations in areas where the winter mean drops to 68° F. There is considerable variation in the length of the immature stages, particularly during the coolest weather. Inasmuch as adults have been kept alive for 10 months and may deposit eggs in lots of a few to 32 daily quite regularly throughout life, the generations become hopelessly confused. While adults are not forced in Hawaii to pass through periods of several months when food is not available for oviposition, females deprived of host fruits for such periods will resume active and normal oviposition when the fruits become avail able. One female deposited 622 eggs between June 4 and September 2. The long adult life, and the ability of the female to deposit eggs regularly succeeding the period of from 4 to 8 days after emergence which is required to complete sexual maturity, make it possible for the annual progeny of a single pair of adults to reach enormous numbers. Attempts at control by clean culture have been failures, owing largely to insurmountable obstacles placed in the way of man by a favorable climate and an unprecedented quantity of varied host fruits. Many fruits and nuts subject to attack grow on huge trees which blossom irregularly, and produce, in many instances, fruit susceptible to attack throughout the year. There is no procedure by which clean culture may be made effective under the present Hawaiian cultural methods. The islands are thoroughly overrun with the fruit fly, and this applies quite as much to the wild guava scrub in pastures, on lava flows, and in mountain valleys and ravines, as it does within the city limits. By far the larger number of host trees and shrubs are grown more for the protection they offer from the semitropical sun and for their ornamental value than for their inedible fruits. The destruction of host vegetation will not be practicable until it can be demonstrated that a distinct advantage would be gained thereby. To destroy all host trees of Honolulu at the present time would be to remove a large percentage of her prized vegetation without any compensating returns. The ideal climatic and host conditions of Hawaii have rendered less effective and impracticable the usual artificial methods of control the value of which has been demonstrated in other countries possessing natural features less favorable to fruit-fly increase. At the present time the only hope of relief lies in the establishment of parasites. Six parasites have been introduced during the past three years and are now well established. While they have more than repaid the Territory of Hawaii for the cost of their introduction by bringing about an improved condition in the coffee-growing industry, it is doubtful whether they will effect a sufficient decrease in the proportion of infested host fruits to be considered efficient factors in control. This conclusion appears inevitable in spite of the remarkable success attendant on their introduction, unless a campaign is inaugurated for a reapportionment of host fruits; otherwise the hordes of adult flies maturing in thick-meated fruits, or in fruits protecting larvæ by other means from attack by parasites, will neutralize the effective work of parasites attacking larvæ in thin-skinned and thinpulped fruits. There is great need of an effective egg parasite that will kill the fruit fly before the larva can do injury. From a practical or commercial standpoint the results of the investigations reported herewith are of value (1) in furnishing data to determine the probable range of this pest should it be introduced and gain a foothold in continental United States; (2) in verifying the practicability of poison sprays; (3) in indicating the utilization of cold-storage temperatures in making safe the movement of fruits from areas which might otherwise be cut off by quarantines from outside markets; and (4) in placing upon a sound basis the banana and pineapple export trade of the Hawaiian Islands. At 50° F. little if any development takes place, and freezing temperatures can be withstood successfully only for short periods. Accumulated data indicate that the Mediterranean fruit fly will not become a serious pest in climates where the mean temperature is below 50° F. during periods covering three months of the year. While Hawaiian conditions are unfavorable to the use of poison sprays, the work of the writers has convinced them that these sprays can be employed as successfully in combating this pest in commercial orchards of California and of Southern States, should they ever become infested, as in Africa and Australia. While at present cold storage is not utilized to modify existing quarantine, it is a recognized fact that, commercially used, it has been of value in safeguarding fruits from additional infestation while en route over long distances. The data set forth herewith indicate for the first time the duration of time required for various temperature ranges to kill the stages of the fruit fly within stored fruits, and from these records it is reasonable to conclude that the certification of properly refrigerated fruit is practicable. When an association of fruit growers or the people discover that refrigeration is financially worth while, there is reason to believe that it will result in the operation of central refrigeration plants under the supervision of officers whose guarantee will insure that all fruits sent out from the plant are absolutely free from danger as carriers of the Mediterranean fruit fly. PUBLICATIONS OF THE UNITED STATES DEPARTMENT OF AGRICULTURE RELATING TO INSECTS INJURIOUS TO CITRUS AND OTHER SUBTROPICAL FRUITS. AVAILABLE FOR FREE DISTRIBUTION BY THE DEPARTMENT. Scale Insects and Mites on Citrus Trees. (Farmers' Bulletin 172.) Control of the Citrus Thrips in California and Arizona. (Farmers' Bulletin 674.) Citrus Mealybug and its Control in California. (Farmers' Bulletin 862.) Argentine Ant: Distribution and Control in the United States. (Department Bulletin 377.) Fumigation of Ornamental Greenhouse Plants with Hydrocyanic-acid Gas. (Department Bulletin 513.) Spraying for White Flies in Florida. (Entomology Circular 168.) FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, GOVERNMENT PRINTING OFFICE, WASHINGTON, D. C. The Melon Fly in Hawaii. (Department Bulletin 491.) Price, 25 cents. Preparations for Winter Fumigation for Citrus White Fly. (Entomology Circular 111.) Price, 5 cents. Mango Weevil. (Entomology Circular 141.) Price, 5 cents. Mediterranean Fruit Fly. (Entomology Circular 160.) Price, 5 cents. Fumigation for Citrus White Fly, as Adapted to Florida Conditions. (Entomology Bulletin 76.) Price, 15 cents. Fumigation Investigations in California. (Entomology Bulletin 79.) Price, 15 cents. Hydrocyanic-acid Gas Fumigation in California. (Entomology Bulletin 90, 3 pts.) Price, 20 cents. Fumigation of Citrus Trees. (Entomology Bulletin 90, pt. I.) Price, 20 cents. Value of Sodium Cyanid for Fumigation Purposes. (Entomology Bulletin 90, pt II.) Price, 5 cents. Chemistry of Fumigation with Hydrocyanic-acid Gas. (Entomology Bulletin 90, pt. III.) Price, 5 cents. White Flies Injurious to Citrus in Florida. (Entomology Bulletin 92.) Price, 25 cents. Orange Thrips, Report of Progress. (Entomology Bulletin 99, pt. I.) Price, 5 cents. Red-banded Thrips. (Entomology Bulletin 99, pt. II.) Price, 5 cents. Natural Control of White Flies in Florida. (Entomology Bulletin 102.) Price, 20 cents. Argentine Ant. (Entomology Bulletin 122.) Price, 25 cents. 119 |