common name: Mediterranean fruit fly
scientific name: Ceratitis capitata (Wiedemann) (Insecta: Diptera: Tephritidae)

Introduction - Synonymy - Distribution - Identification - Life History and Habits - Hosts - Mediterranean Fruit Fly Host List - Detection and Survey - Management - Selected References

Introduction

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the world's most destructive fruit pests. The species originated in sub-Saharan Africa and is not known to be established in the continental United States. When it has been detected in Florida, California and Texas, especially in recent years, each infestation necessitated intensive and massive eradication and detection procedures so that the pest did not become established.

adult

Because of its wide distribution over the world, its ability to tolerate cooler climates better than most other species of tropical fruit flies, and its wide range of hosts, it is ranked first among economically important fruit fly species. Its larvae feed and develop on many deciduous, subtropical, and tropical fruits and some vegetables. Although it may be a major pest of citrus, often it is a more serious pest of some deciduous fruits, such as peach, pear, and apple. The larvae feed upon the pulp of host fruits, sometimes tunneling through it and eventually reducing the whole to a juicy, inedible mass. In some of the Mediterranean countries, only the earlier varieties of citrus are grown, because the flies develop so rapidly that late season fruits are too heavily infested to be marketable. Some areas have had almost 100% infestation in stone fruits. Harvesting before complete maturity also is practiced in Mediterranean areas generally infested with this fruit fly.

In this age of jet transportation, the "medfly" can be transported from one part of the world to some distant place in a matter of hours, which greatly complicates efforts to contain it within its present distribution. Once it is established, eradication efforts may be extremely difficult and expensive. In addition to reduction of crop yield, infested areas have the additional expense of control measures and costly sorting processes for both fresh and processed fruit and vegetables. Some countries maintain quarantines against the medfly, which could jeopardize some fresh fruit markets if it should become established in Florida.

Synonymy

Ceratitis citriperda MacLeay
Ceratitis hispanica De Brême
Paradalaspis asparagi Bezzi
Tephritis capitata Wiedemann
Ceratitis capitata (Wiedemann)

Distribution

Countries with established infestations include (CABI 1999): Mediterranean fruit fly infestations in the United States occurred in:

1929-1998 Florida infestations

Identification

The medfly has no near relatives in the Western Hemisphere. The adults are slightly smaller than a house fly and have picture wings typical of fruit flies. They can be distinguished fairly readily from any of the native fruit flies of the New World.

Egg: The egg is very slender, curved, 1 mm long, smooth and shiny white. The micropylar region is distinctly tubercular.

eggs

Larva: Larva are white with a typical fruit fly larval shape, i.e. cylindrical maggot-shape, elongate, anterior end narrowed and somewhat recurved ventrally, with anterior mouth hooks, and flattened caudal end. The last instar is usually 7 to 9 mm in length, with eight ventral fusiform areas. The anterior buccal carinae are usually nine to 10 in number. The anterior spiracles are usually nearly straight on dorsal edge of tubule row (often more straight than illustrated). There are usually nine to 10 tubules, although there may be seven to 11.

larva

mature larva

head and buccal carinae

anterior spiracles of larva

The cephalo-pharyngeal skeleton has a large convex mouth hook each side, approximately 2X hypostome in length. The hypostomium has prominent, rounded subhypostomium; post-hypostomial plates curved dorsally to the dorsal bridge, fused with sclerotized rays of central area of dorsal wing plate. The parastomium is prominent. The anterior of the dorsal bridge has a prominent sclerotized point. The dorsal wing plate is nearly as long as the pharyngeal plate. The median area is relatively unsclerotized. The pharyngeal plate is elongate, with prominent median hood and anterior sclerotized area.

cephalo-pharyngeal skeleton

The caudal end has bifurcate or paired dorsal papillules (D1 and D2) on small mount of relatively flat plate; intermediate papillules (I1-2) as a line of fused elevations on a very enlarged subspiracular tubercle, plus a remote I3 at approximately 45 degrees from I1-2; L1 on the median edge of the caudal end; V1 not prominent; posterior spiracles elongate (4.5 to 5X width), with dorsal and ventral spiracles angled away from relatively planar median spiracle; interspiracular processes (hairs) usually not branched; anal lobe bifid or entire.

caudal end of larva

posterior spiracles

anal lobes of larva

Larval Diagnosis The primary diagnostic characters for Mediterranean fruit fly larvae involve the anterior spiracles, the buccal carinae, and the prominent subspiracular tubercles of the caudal end. The anterior spiracles have the tubule edge relatively straight dorsally and the tubule number usually is nine to 10, although it can be from seven to 11. The buccal carinae number nine to 10. The caudal end has two prominent subspiracular tubercles, each with a crescent of irregularly fused papillules (approximately equivalent to 11-2). The anal lobe is either bifid or entire. The pharyngeal skeleton is distinctive in overall configuration, particularly the enlarged subhypostomium of the hypostomium (posterior to each mouth hook). There is a heavily sclerotized dorsal bridge point at the anterior of the dorsal wing plate. The shape of the interior sclerotizations of the dorsal wing plate and the hood of the pharyngeal plate are also distinctive for the species.

The features of the larvae of C. capitata, as noted in the description, are variable to some degree as indicated. Most previous illustrations of the cephalo-pharyngeal skeleton of the species have not shown the pharyngeal plate hood, and details of the illustrations also vary among themselves (see Greene 1929, Phillips 1946). The figure of the cephalo-pharyngeal skeleton in Greene (1929) appears not to be very accurate. The supposed supernumerary lateral papillules of the caudal end, noted by Phillips (1946), are not usually evident in specimens or at most represent only slight plate elevations on the very lateral edge dorsal to L1.

Larvae examined came from verified samples from Florida, Hawaii, and Portugal (all are in the larval collection of the Museum of Entomology, Florida State Collection of Arthropods).

Pupa: The pupa is cylindrical, 4 to 4.3 mm long, dark reddish brown, and resembles a swollen grain of wheat.

pupae

pupal views

adult emerging

Adult: The adult fly is 3.5 to 5 mm in length. The color is yellowish with brown tinge, especially on abdomen, legs, and some markings on wings. The lower corners of the face have white setae. Eyes are reddish purple (fluoresce green, turning blackish within 24 hours after death). Ocellar bristles are present. The male has a pair of bristles with enlarged spatulate tips next to the inner margins of the eyes. The thorax is creamy white to yellow with a characteristic pattern of black blotches. Light areas have very fine white bristles. Humeral bristles are present. Dorsocentral bristles are anterior of the halfway point between supraalar and acrostichal bristles. The scutellum is inflated and shiny black. The abdomen is oval with fine black bristles scattered on dorsal surface and two narrow transverse light bands on basal half.

thorax

Wings, usually held in a drooping position on live flies, are broad and hyaline with black, brown, and brownish yellow markings. Ther is a wide brownish yellow band across the middle of the wing. The apex of the wing's anal cell is elongate. There are dark streaks and spots in middle of wing cells in and anterior to anal cell.

wing pattern

The males are easily separated from all other members of this family by the black pointed expansion at the apex of the anterior pair of orbital setae. The females can be separated from most other species by the characteristic yellow wing pattern and the apical half of the scutellum being entirely black (White and Elson-Harris 1994). The female's extended ovipositor is 1.2 mm long.

adult male - dorsal view

adult - lateral view

Life History and Habits

The length of time required for the medfly to complete its life cycle under typical Florida summer weather conditions, and on which eradication schedules in Florida are based, is 21 to 30 days. A female medfly will lay one to 10 eggs in an egg cavity 1 mm deep, may lay as many as 22 eggs per day, and may lay as many as 800 eggs during her lifetime (usually about 300). The number of eggs found at any time in the reproductive organs is no indication of the total number of eggs an individual female is capable of depositing, as new eggs are being formed continually throughout her adult life. Females usually die soon after they cease to oviposit.

stages in life cycle

Eggs are deposited under the skin of fruit which is just beginning to ripen, often in an area where some break in the skin already has occurred. Several females may use the same deposition hole with 75 or more eggs clustered in one spot. When the eggs hatch, the larvae promptly begin eating, and at first tunnels are formed, but may keep close together in feeding until nearly full grown. Fruit in a hard or semiripe condition is better for oviposition than fully ripened fruit. Ripe fruit is likely to be more juicy, and such fruits often are associated with a high mortality of eggs and young larvae.

Females will not oviposit when temperatures drop below 60.8°F (16°C) except when exposed to sunlight for several hours. Development in egg, larval, and pupal stages stops at 50°F (10°C). Pupae carry the species through unfavorable conditions, such as lack of food, water, and temperature extremes. During warm weather eggs hatch in 1.5 to three days. The duration of the egg stage is considerably increased by lower temperatures.

Larvae pass through three instars. Larval life may be as short as six to 10 days when the mean temperatures average 77 to 79°F (25 to 26.1°C). The kind and condition of the fruit often influence the length of the larval stage. In citrus fruits, especially limes and lemons, it appears to be longer. Thus larvae require 14 to 26 days to reach maturity in a ripe lemon, as compared with 10 to 15 days in a green peach. Larvae leave the fruit in largest numbers at or just after daybreak and pupate in the soil or whatever is available.

Minimum duration of the pupal stage is six to 13 days when the mean temperature ranges from about 76 to 79°F (24.4 to 26.1°C). Back and Pemberton (1915) noted that this period may be increased to at least 19 days when the daily temperature means drop to about 69 to 71°F (20.6 to 21.7°C).

Adults emerge in largest numbers early in the morning during warm weather and emerge more sporadically during cool weather. They can fly short distances, but winds may carry them a mile or more away. Copulation may occur at any time throughout the day. Newly emerged adults are not sexually mature. Males often show sexual activity four days after emergence, and copulation has been observed five days after emergence. Both sexes are sexually active throughout the day. When the daily mean temperature averages from 76 to 78°F (24.4 to 25.6°C), most females are ready to mate from six to eight days after eclosion. Oviposition may take place as early as four to five days after emergence during very warm weather, but not for about 10 days when temperatures range between 68 to 72°F (20 to 22.2°C) (Back and Pemberton 1915).

Adults die within four days if they cannot obtain food. Usually about 50% of the flies die during the first two months after emergence. Some adults may survive up to six months or more under favorable conditions of food (fruit, honeydew, or plant sap), water, and cool temperatures. When host fruit is continuously available and weather conditions favorable for many months, successive generations will be large and continuous. Lack of fruit for three to four months reduces the population to a minimum.

Hosts

The Mediterranean fruit fly attacks more than 260 different fruits, flowers, vegetables, and nuts. Thin-skinned, ripe succulent fruits are preferred. Host preferences vary in different regions. Although several species of cucurbits have been recorded as hosts of the medfly, they are considered to be very poor hosts. Some hosts have been recorded as medfly hosts only under laboratory conditions and may not be attacked in the field. Knowledge of the hosts in one country often aids in correctly predicting those which are most likely to be infested in a newly infested country, but what may be a preferred host in one part of the world may be a poor host in another.

larval infestation

adult female ovipositing eggs

Mediterranean Fruit Fly Host List

Attached is a world list of hosts grouped according to their importance according to best available information.

Heavily or Generally Infested

Detection and Survey

A primary method of collecting larvae is by cutting infested fruit. Fully grown larvae, when the surrounding air temperature is warm, flex and "jump" repeatedly as much as 25 mm when removed from fruit. Larval identification is extremely difficult, so that when feasible it is best to rear them to adults for identification. If collected larvae must be killed, they should be placed in hot water and then transferred to 70% isopropenol. Larval identification is based primarily on characters of mature 3rd instar larvae.

Adults are collected primarily by use of sticky-board traps and baited traps (USDA 1997). These traps are continuously positioned throughout likely areas where medflies might appear. In Florida, Inspectors from the Department of Agriculture and Consumer Services-Division of Plant Industry continually monitor the traps for the appearance of pest fruit flies. Once an adult Mediterranean fruit fly is positively identified, the number of baited traps throughout that area is greatly increased to capture the flies and remove them from the environment, and to serve as a monitoring tool for the effectiveness of the eradication program. Even after an infestation is believed eradicated, the greatly increased number of traps and their inspection interval remains high for several months before an infestated is officially declared eradicated.

older medfly trap

newer medfly trap

Management

As a Mediterranean fruit fly infestation falls under the control of Florida's regulatory agency - the Department of Agriculture and Consumer Services (FDACS) and its Division of Plant Industry (DPI), there are no University of Florida management recommendations. Plus treatment strategies change in an environment of public concern about aerial application of insecticidal baits.

For the 2010 infestation, the following treatments are being used by FDACS-DPI and the USDA (FDACS 2010b):

USDA-ARS scientists in Hawaii and Texas collaborated in investigating phloxine B, better known as the FDA-approved red dye number 28. The dye proved to be as effective as malathion-bait sprays and might be a safe, effective alternative to previously used aerially-applied malathion insecticide baits. Medflies often share regurgitated food. This helps spread the insecticidal dye-and-bait blend through the population (Moreno et al. 2001).

adult feeding on bait-dye

adult regurgitating food

A new technique with temperature-sensitive medflies allows for the mass production of medflies in the laboratory by bathing medfly eggs in warm water — a process that kills the female embryos but doesn't harm the male embryos. In the pupal stage, the males can be irradiated to render them sexually sterile (USDA 2000).

USDA-APHIS, in cooperation with threatened states, has established action plans that go into effect when fruit flies are trapped and reported (USDA 2008).

In Florida, the FDACS-Division of Plant Industry will cooperate with USDA-APHIS in regulating the actions of both commercial entities and homeowners.

Selected References

Authors: M.C. Thomas, J.B. Heppner, R.E. Woodruff, H.V. Weems, and G.J. Steck, Florida Department of Agriculture and Consumer Services, Division of Plant Industry; and T.R. Fasulo, University of Florida
Originally published as DPI Entomology Circulars 4, 230 and 273. Updated for this publication.
Photographs: USDA, and Jeffery Lotz, Division of Plant Industry; Ken Walker, Museum Victoria, Melbourne, Australia; Anne-Sophie Roy, European and Mediterranean Plant Protection Organization;
Graphics: Division of Plant Industry
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-214
Publication Date: July 2001. Latest revision: September 2010.
Copyright 2001-2010 University of Florida

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