Fruit Flies (Diptera: Tephritoidea): Biology, Host Plants, Natural Enemies, and the Implications to Their Natural Control

Brazil is the third world largest producer of fruits, surpassed only by China (94.4 millions of tons) and India (51.14 million tons) (Vitti, 2009). The fruit growing area in Brazil currently takes up 2.3 millions of hectares, with an annual production superior to 36.8 millions of tones. The horticulture generates six millions of direct jobs, totalizing about 27% of total labor force employed in agriculture in the Country, and makes a gross domestic product (GDP) of about US$ 11 billion. In the farms of fruit growing, in general, there are a demand for intensive and qualified labor, creating jobs and ensuring a rural Well-being of the farmers and their employees, both on small farms as on large farms. However, Brazil occupies the 17th position among world exporters of fruits (Ibraf, 2009; Vitti, 2009).


Introduction
Brazil is the third world largest producer of fruits, surpassed only by China (94.4 millions of tons) and India (51.14 million tons) (Vitti, 2009). The fruit growing area in Brazil currently takes up 2.3 millions of hectares, with an annual production superior to 36.8 millions of tones. The horticulture generates six millions of direct jobs, totalizing about 27% of total labor force employed in agriculture in the Country, and makes a gross domestic product (GDP) of about US$ 11 billion. In the farms of fruit growing, in general, there are a demand for intensive and qualified labor, creating jobs and ensuring a rural Well-being of the farmers and their employees, both on small farms as on large farms. However, Brazil occupies the 17th position among world exporters of fruits (Ibraf, 2009;Vitti, 2009).
Part of Brazilian fruit production is lost in the field due the attack by larvae of different species of fruit flies (Diptera: Tephritoidea). Herein, fruit flies are referred as the guild of all specialized species with frugivorous larvae, that in South America, especially in Brazil, belong to two families: Tephritidae and Lonchaeidae (Diptera: Tephritoidea) (Uchoa & Nicácio, 2010). On the other hand, the fruit flies are interesting animals of the scientific point of view, because they have polytene chromosomes like those found in species of Drosophila (Drosophilidae), which are very important for genetics studies. Fruit Flies also can be easily reared in the laboratory to serve as experimental animals for research in several areas of the biological and environmental sciences (Uchoa et al., 2004).
The fruit flies belong to two families: Tephritidae and Lonchaeidae (Tephritoidea). They have great economic importance because they are considered the key pests that most adversely affect the production and marketing of fruits and vegetables around the world. The tephritids are able of inserting the ovipositor to drop their eggs into the living tissues of host plants, such as green fruit, fruit in process of maturation or ripe fruits. If females of Lonchaeidae lay their eggs inside or over the fruits, flowers, or inside terminal shoots of Euphorbiaceae is still unknown. According Lourenção et al. (1996), Neosilba perezi (Romero & Ruppel) is a key pest in shoots of cassava clones. Both families of fruit flies cause direct and indirect damages. The direct ones are because their eggs hatch and the larvae eat the underlying flesh of the fruits. The indirect damage is due to depreciation of the fruits in the

Fruit flies species with economic importance in South America
The genus Anastrepha is originally from the Neotropical Region, with a total of 252 species described worldwide to date, being 112 recorded in Brazil Norrbom & Uchoa, 2011), where about 14 species of Anastrepha (Tab. 1), along with Bactrecera carambolae, Ceratitis capitata (Wiedemann) (Tephritidae), and some species of Dasiops and Neosilba (Lonchaeidae) are the main species of fruit flies with actual or potential economic importance to the Brazilian crop fruits or vegetables .
Bactrecera carambolae is native to the Indo-Australian region. It attacks at least 26 species of host fruits worldwide, most of them of commercial interest (e.g., Star Fruit, mango, sapodilla, cherry, guava, jabuticaba, rose apple, jackfruit, breadfruit, orange, tangerine, tomato, etc.). It was introduced in Northern Brazil (Oiapoque, Amapá) in 1996 from French Guiana, carried Lonchaeidae is the second family of fruit flies with economic importance in South America, where some species of the genera Dasiops and Neosilba are primary pests in crop fruits. The species of Dasiops attack cultivated or wild passion fruit species: green or ripe fruits, or floral buds (Passifloraceae), depending on the Dasiops species (Norrbom & Mcalpine, 1997;Uchoa et al., 2002;Uchoa & Nicácio, 2010). The Neosilba species are generally polyphagous, attacking many species of fruit, native or exotic, cultivated or wild ones. The Neosilba species most commonly involved in the infestation of fruits and vegetables are: N. zadolicha Steyskal & McAlpine, N. pendula (Bezzi), N. glaberrima (Wiedemann), and N. inesperata Strikis & Prado. These four Neosilba species, plus N. perezi, are considered of greatest economic importance in South America because of their damage in crop fruits, vegetables, or in cassava plantations (Lourenção et al., 1996;. From the species of fruit flies pests that occurs in Central and South America, Anastrepha obliqua (Macquart), Anastrepha fraterculus (Wiedemann), and Ceratitis capitata, are the most polyphagous and with greater distribution in Brazil (Uchoa & Nicácio, 2010), Argentina Guillén & Sánchez (2007), Bolivia, Ovruski et al. (2009), Colombia, Canal (2010, Venezuela, Katiyar et al. (2000), and Peru, Harris & Olalquaiga (1991). Similar pattern is reported in Central America (Reyes et al., 2007), where Anastrepha ludens also occurs. Consequently, that that three first species are the most often involved in the colonization of fruits and vegetables sold in the market retailers. The status of these three species as pests of horticulture is motivated by three main factors: the existence of several host species, their wide distribution in the Neotropics (from Mexico to Argentina), and the direct damage that they can cause to fruits and vegetables (Uchoa & Nicácio, 2010). Populations of the Mexican fruit fly Anastrepha ludens occurs in North America: Mexico and USA (Florida); in Central America: Belize, Costa Rica, El Salvador, Guatemala, Honduras and Nicaragua, but it is not recorded in South America (Oliveira et al., 2006).

Why the control of the fruit flies is so difficult?
The control of fruit flies (including lance flies) in the South American orchards is still done mainly through of spray chemical pesticide. However, worldwide, the widespread use of chemical pesticides to protect agricultural products against insects and other arthropod pests is of increasing concern (Cancino et al., 2009), especially because of consequent environmental pollutants, and human food contamination by pesticides residues with disastrous consequences on our health and environments.
The adult female of the tephritid fruit flies (e.g. Anastrepha spp., Bactrocera spp., Rhagoletis spp., and Ceratitis capitata) are able to lay their eggs inside the fruit tissue, pouncing the skin and fruit pulp with their aculeus (ovipositor). After oviposition the wounds over the fruit surface become healed, and the eggs can mature and hatch inside the fruit tissue. The newly emerged larvae are now sheltered from the external environment, making difficult any effort with pesticides to control them.

Life history of Anastrepha species (Trypetinae: Tephritidae)
The complete life cycle of Anastrepha fraterculus in the field is still unknown, but under laboratory conditions (25 o C, and 70-80% RH), the life cycle from egg to the first female oviposition, occurred in about 80 days. The adult longevity in that condition was 161 days to both males and females. The eggs hatch in about 3 days, larvae is completed around 13 days, pupae emerged in about 14 days, and the female gained sexual maturation and started oviposition after 7 days from emergence (Salles, 2000). Differently from other phytophagous groups of Diptera, the adult females of several Anastrepha species need to feed on proteinaceous materials to maturing their eggs.
In nature or in laboratory, when the third-instar larvae of Anastrepha spp. are fully mature, they fall off from the fruit and dig in the soil to pupation, that occurs at depths between 2 and 5 cm (Hodgson et al. 1998).  found that depending on the climatic conditions (between 15-30 o C, and 60-90% RH) the emergence is faster. Under this condition, the adults can emerge, depending on the species, between 14 and 22 days after they have buried themselves in the soil to pupation.
The sexual behavior of Anastrepha sororcula Zucchi was studied in laboratory. This species is a key pest of guava (Psidium guajava L.) in Brazil. The age of sexual maturation to the males of A. sororcula in laboratory was completed between 7 and 18 days, at an average, 12 days after emergence. The males exhibited signaling behavior to the females, characterized by the distension of the pleural area of the abdomen, forming a small pouch on each side, and by the protrusion of a tiny membranous pouch of rectal cuticle that surrounds the anal area. During this display, the males produced rapid movements of wing vibrations, producing an audible sound. A droplet was liberated from the anal area during wing vibration movements. After attracting the females, the males accomplished a series of elaborated movements of courtship behavior (Fig. 1). On the other hand, females became sexually mature between 14 and 24 days, on average, at 19 days after emergence. The daily exhibition of sexual activities was confined almost exclusively to the period from 16:00 to 17:30h. A. sororcula presented a sharp protandry pattern (Facholi & Uchoa, 2006). These asynchronous developments between males and females of fruit flies may play an important evolutionary role. If males and females of the same progeny (offspring) reach sexual maturity at different times in nature, the chance of inbred mating decreases, which increases the genetic variability of the species . Male signaling to the female with wing vibration, abdominal tip distension, and protrusion of their anal pouch; (B) the female attracted to the male approaches, and goes running to that chosen one, making alternating movements of rotation with their wings; (C) the male fly forward to mount the female, trying the copulation, or sometimes, he rises by the head of the female trying the copulation; (D) male with hind legs, raises the ovipositor of the female to connect their genitals for coupling; (E) regularly the male vibrates their body over the female's body; (F) the male goes down from female dorsum and both walk with their heads diametrically opposed for the separation of their genitals, and (G) after decoupling, both start rubbing hind legs on their terminalia (Facholi & Uchoa, 2006).
The longest fase on life cycle of Anastrepha species is, probably, adult. For some studied species (e. g. A. fraterculus and A. sororcula) in laboratory conditions (around 25-27 o C, 60-80% RH) they are able to live for about 180 days. Probably this trait enables the survival some species of Anastrepha in natural environment, enabling them to wait for the adequate stage of development of their host fruit in nature.

Host plants to fruit flies pests in South America
Although Anastrepha is the most biodiverse genus of Neotropical fruit flies, only 14 species are polyphagous, they are with a wide distribution in South America, and able to attack grown fruit and/or vegetables of commercial value. Anastrepha pickeli Lima has been recorded as polyphagous, because it is reported breeding in two species of different families (Uchoa et al., 2002;Zucchi, 2008). But, taking in account that the fruits of Manihot esculenta Crantz (Euphorbiaceae), and that of Quararibea turbinata (Swartz) (Bombacaceae), are not edible, A. pickeli is not considered a key pest (Tab. 1).
Ceratitis capitata is cosmopolitan, one of the most important key pest of fruit and vegetable crops worldwide, and certainly, the most widespread species of frugivorous tephritid around the world. This species feeds in more than 400 fruit species from 75 plant families. In Brazil, C. capitata is recorded in 60 species of host fruits from 22 families, of which 22 are native (Uchoa et al., 2002;Uchoa & Nicácio, 2010)  Herein are considered species with **real economical importance those that have been historically reared from cultivated fruit species with economic value and, with *potential economical importance those that the adults are polyphagous and were reared from some genera of fruit trees in which occur species of fruit with commercial value.
The knowledge of trophic interactions between frugivorous Tephritoidea and their host plants is absolutely necessary to guide strategies for integrated management of fruit fly pests (polyphagous or oligophagous), and for the conservation of stenophagous and monophagous species in their natural environments. Currently in Brazil, from the total of 112 species of Anastrepha reported in our territory, are known the host plants for only 61 species (54.46%), being unknown where 51 Anastrepha species (45.54%) are breeding neither whom are their natural enemies .

Native parasitoids of Anastrepha species and Ceratitis capitata
Hymenoptera parasitoids are the most important natural enemies of pest tephritoid larvae throughout both the Neotropical and Nearctic Regions. These entomophagous insects help reduce naturally, sometimes substantially, populations of Tephritidae and Lonchaeidae pests in the field (Ovruski et al., 2009;Uchoa et al., 2003). Mass-rearing and augmentative releases of braconid parasitoids have been considered an important component of area-wide management programs for some species of fruit flies, including widespread polyphagous species of Anastrepha and Ceratitis capitata (Marinho et al., 2009;Palenchar et al., 2009).
Biological control of frugivorous tephritoid larvae with native parasitoids is a promising component of integrated pest management programs (IPM), because it is environmentally safe and works in synergy with sterile insect technique. Braconidae is the most abundant and species rich parasitoid family of fruit flies in the Neotropical Region. Species of this group also serve as bioindicators of the presence and absence of populations of their host insects ).
Tritrophic interactions among wild tephritoids, their host plants and parasitoids, have been a largely neglected field of study in some regions. It could suggest possible applications for native parasitoid species upon frugivorous tephritoid key pests (Cancino et al., 2009). The autochthonous parasitoids are particularly interesting, because of their evolved interactions over extensive periods of time with their hosts , they can be effective in lowering pest populations in orchards (Cancino et al., 2009), keeping tephritoids outbreak in check without diminishing the local biodiversity, as may occur with the use of exotic natural enemies Uchoa et al., 2003). Parasitism rates found in surveys in which the fruits were removed from the field and carried to laboratory condition, certainly are unreal, because the fruits were picked up from the natural environments, with possibly, some eggs, and larvae of first and second instars of the fruit flies. So, when this immature tephritoids have left the field and have arrived in the laboratory, they have had no more chance to be parasitized (Uchoa et al., 2003). Another mortality factor related of parasitoid attack that is not measured by percentage of parasitism is the damage caused by the scars left by the ovipositor of parasitoid, even when ovipositions failed, and the possibility of subsequent infections by viruses, bacteria, fungi, Fruit Flies (Diptera: Tephritoidea): Biology, Host Plants, Natural Enemies, and the Implications to Their Natural Control 281 protozoa and nematodes  on the frugivorous larvae of tephritoids. There are still no methodologies available, however, to unambiguously to evaluate these causes of mortality to immature frugivorous flies, and this is an area that will require further research. In the future is important to look for oviposition scars by parasitoids upon the third-instar larvae or puparium of dead tephritoids to establish if they are correlated or not to death of flies . Nine native species of braconid parasitoids have been recorded in several states of Brazil, and in other South American Countries. The most promising species to study with the view to apply in biocontrol programs against fruit fly pests are Doryctobracon areolatus, Utetes Fruit Flies (Diptera: Tephritoidea): Biology, Host Plants, Natural Enemies, and the Implications to Their Natural Control 283 anastrephae and Opius bellus (Tab. 2), because they are ubiquitous, frequent and abundant in several regions of South America. Going forward is important to focus in studies on their biology and behavior, in order to multiply them in laboratory for use in programs of integrated pest management in horticulture.

Food attractants, parapheromones and pheromones to fruit flies
Three kinds of attractants have been proposed to catch fruit flies in traps: food lures, parapheromones, and sex pheromones. Although the McPhail traps baited with food lures are the most usually employed in the field to catch tephritids worldwide, they have low attractiveness to fruit flies, normally attracting adults only from a short distance, about 10 m far from the source, depending if the wind is blowing continuously. The most usual baits are hydrolyzed proteinaceous from soybean, corn or torula yeast. According to Aluja et al. (1989) only 30% of the flies that are attracted to near the traps with food baits are actually captured. Some blends of synthetic dry food lures (ammonium acetate + trimethylamine hydrochloride + putrescine) have been prepared to catch Ceratitis capitata, Anastrepha and Bactrocera species (Leblanc et al., 2010), but like the hydrolysate proteinaceous baits, it has the inconvenient of catching nontarget insects from several Orders, such as Diptera (e.g. Calliphoridae, Tachinidae), Lepidoptera, Hymenoptera, Neuroptera, Orthoptera, and in some places, till small vertebrates such as amphibians (Uchoa, M. A., unpubl.).
The compounds called parapheromones, such as trimedlure, cuelure and methyl eugenol are efficient on capturing fruit flies. They have been applied in traps to capture species of Ceratitis, Dacus and Bactrocera in the field. Differently from the common food baits, like hydrolyzed proteinaceous (corn, soybean) or torula yeast, the parapheromones are considered more selective for catching fruit flies. This is an interesting trait of these chemicals due to avoid the capture of non-target insects. But, on other hand, due the fact they capture almost exclusively male specimens, they are a problem in cases when the aim of the research is to survey the diversity of fruit flies species. Because, in some taxa, the accurate identification is based mainly in females. Furthermore, they are comparatively more expensive and harder to find in the local markets than the food baits.
The pheromones are considered biochemically ideals to control fruit flies, because generally they are species-specific, environmentally safe, being non-toxic till to the target species. However, unlike other insects such as moths, beetles, and the true bugs; Tephritidae have a complex communication system, involving short range vision and acoustic signaling, beyond the chemical language (see life history of Anastrepha species). Although in Mexico has been reported the capture of A. suspensa females in traps baited with virgin males (Perdomo et al., 1975, 1976), in Brazil, Felix et al. (2009 found that Jackson and McPhail traps baited with food bait were significantly more attractive to females of Anastrepha sororcula that traps baited with fruit fly sexually mature conspecific males. The last authors did not found significant capture of A. sororcula females in the traps baited with conspecific virgin males releasing sex pheromone; conspecific female neither conspecific couples. So, probably, sex pheromone of Anastrepha fruit flies did not show high potential to be applied in field to control this group of horticultural pests. For Lonchaeidae, only food baits based on protein hydrolysates have been used. Lonchaeids are well captured into the same McPhail traps used for sampling of tephritids.

Life history of Dasiops and Neosilba species (Lonchaeidae)
The species of Dasiops (Dasiopinae) are probably stenophagous (see Aluja & Mangan, 2008), feeding mainly on flowers or fruits Passiflora spp. (Malpighiales: Passifloraceae) Uchoa et al., 2002). On other hand, Neosilba species (Lonchaeinae) are mainly polyphagous, attacking a broad array of host plant groups in South America (Tab. 3). Neosilba perezi attacks the terminal buds of cassava (Euphorbiaceae), but this behavior of feeding on tissue different of fruits and flowers is uncommon for other Lonchaeidae species in South America, where the lance flies colonize fruits of both, native or exotic species (Tab. 3). Caires et al. (2009)

Pest status of Dasiops and Neosilba
Up to date at least 34 species of Lonchaeidae that feed on live tissue of plants are reported in Americas. Dasiops species are probably stenophagous (Aluja & Mangan, 2008), feeding in flowers or fruits of Passiflora (Passifloraceae). Some of them (e.g. D. inedulis), are important pest in flower buds of passion fruits in South America (Peñaranda et al., 1986;Uchoa et al., 2002). By other hand, some species of the same genus have been proposed to be biocontrol agents for weed Passiflora introduced in Hawaii (Norrbom & McAlpine, 1997

Native parasitoids of Lonchaeidae species
Eight species of Eucoilinae parasitoids (Figitidae: Cynipoidea) have been associated to frugivorous larvae of Neosilba in Brazil. However, up to date, only four of these parasitoid species were associated to their host larvae and host plant. Aganaspis nordlanderi Wharton was recovered from pupae of N. pendula (Bezzi) whose larvae were feeding in fruits of tangerine, Citrus reticulata Blanco (Rutaceae). Lopheucoila anastrephae (Rhower) was reared from pupae of N. batesi (Curran), obtained as larvae in Passiflora fruits (Passifloraceae), and from N. pendula attacking orange, Citrus sinensis (L.) (Rutaceae). Odontosema anastrephae Borgmeier was recovered from larvae of N. pendula in fruits of Caryocar brasiliense Camb. (Caryocaraceae), and Trybliographa infuscata Gallardo, Díaz & Uchoa was recovered from N. pendula in orange, Citrus sinensis and Caryocar brasiliense. In all the cases the species of Neosilba were collected in the larval third-instars, and only one specimen of Eucoilinae emerged from each pupa (Tab. 4).

Current status and future perspectives on the control of fruit flies
Currently the control of fruit fly is made with chemical pesticide spraying, a concerning reality because most tropical fruits are eaten raw, making the residue over them an environmental and human health problem. In Brazil, some farmers have reduced the impact of pesticides in orchards, spraying sugar solution on certain rows of fruit trees in the orchards, where fruit flies are attracted to the food source. So, they spray insecticides in this crowd of tephritids. This practice reduces the amount of insecticides in the environment, decreasing the risk of residues in the fruits.
Several researchers in the Americas (e.g. in Brazil) are looking for powerful and specific attractants to catch fruit flies in traps. These natural chemicals can be present in the host fruits of the fruit flies. If isolated, identified and synthesized these natural attractants can be important in both cases: surveys on species diversity in natural environments, and for the management of pest species in orchards, enabling the reduction in the use of chemical insecticides. This technique in association with biological control with native parasitoids, probably, will be possible in the near future. Doryctobracon areolatus and Utetes anastrephae are good candidates for keeping population of Anastrepha species and Ceratitis capitata in low levels, making possible to produce clean fruits and vegetables.

Conclusions
Anastrepha is the most biodiverse and economically important genus of Tephritidae in Brazil, but from the total of 112 species reported in the Country to date, only 14 species can be considered as pest or potential pests. In Brazil two very economically important tropical species of fruit flies: Anastrepha ludens (Loew) and Anastrepha suspensa (Loew) do not occur.
In South America occur at least eight species of Braconidae parasitoids. Doryctobracon areolatus, Utetes anastrephae, and Opius bellus are the most ubiquitous and with wide distribution, being D. areolatus the best candidate for biological control programs of Anastrepha species, and maybe also, for Ceratitis capitata. There are not enough studies to know how Neosilba, and Dasiops species lay their eggs in the host plants: if endophytic, like the tephritids, or if the eggs are scattered in the target part of the host plants and the newly hatched larvae are able to penetrate in the plant tissue by them. The Lonchaeidae can occupy the same ecological niche occupied by the tephritids. In some host plants, the lonchaeids can be more abundant and important as pest that the tephritids, including some fruit species with economic importance, such as Citrus spp. (Rutaceae), Spondias dulcis Parkison (Anacardiaceae), and species of Passiflora (Passifloraceae). The Lonchaeidae have, at least, eight species of Eucoilinae (Figitidae) parasitoids in Brazil, but the biology of both groups (lonchaeids and its parasitoids) is unknown. Lopheucoila anastrephae, Trybliographa infuscata and Aganaspis nordlanderi, have been the most abundant and frequent parasitoids in larvae of third-instars of Neosilba species in Citrus orchards in Brazil.

Research needs
For solving some bottlenecks to enable the monitoring and control of fruit flies with nonpolluting methods, the following topics are specially in need of researches: regional surveys