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Anastrepha and Toxotrypana:
descriptions, illustrations, and interactive keys

DELTA Home

Allen L. Norrbom, Cheslavo A. Korytkowski, Roberto A. Zucchi, Keiko Uramoto, George L. Venable, Jerrett McCormick and Michael J. Dallwitz

Introduction

Warning. This identification system is not fully completed. Some species have not been fully scored and cannot be eliminated in the identification process, and some characters and species have not been illustrated. Despite these limitations, we have made the system available because it has reached the stage where it functions for most species and there are no other comprehensive identification tools available for this economically important group of fruit flies. Users need to be aware of these limitations in using the system. Also see ‘Scope and limits’ (below) and Hints on using the keys.

Anastrepha Schiner and Toxotrypana Gerstaecker are the most economically important genera of true fruit flies (Diptera: Tephritidae) in the American tropics and subtropics. Together they also form the most diverse clade of fruit flies in the region, with more than 250 valid species and numerous undescribed species (Norrbom et al. 1999a,b, 2004a, Norrbom & Korytkowski 2009). Because there are so many species, many of which are extremely similar, the development and use of traditional dichotomous keys for their identification is very difficult. Although there are several regional keys (e.g., Zucchi 2000 for Brazil, Hernandez-Ortiz 1992 for Mexico), the most recent comprehensive keys, that by Stone (1942a), and a revised version by Steyskal (1977), are now badly out of date.

This system attempts to bring together in a single package all of the relevant taxonomic information for these species, as well as images for each species, and provides a choice of two electronic keys (Intkey or Lucid) that allow the user much greater flexibility to use this information than in a dichotomous key. The interactive keys and descriptions in this system were produced from a data matrix in DELTA format (Dallwitz 1980; Dallwitz, Paine, and Zurcher 1993, 1999), and allow the user to access the latest taxonomic information and images in the most efficient manner. The system provides a more flexible and rapid method for morphological indentification of all species of Anastrepha and Toxotrypana. Future versions will be updated on this site. We will be grateful for notification of corrections or additional information.

Scope and limits

Like most identification systems, this system is not a panacea. There are unresolved problems in the taxonomy of Anastrepha and Toxotrypana, including species and species groups that need further revision, and unresolved species complexes such as the hamata/sagittata complex and the fraterculus complex. These problems were beyond the scope of this project, thus not all specimens in these groups can be identified to species level using this system. We also are aware of additional undescribed species that have not been included in the system but could be encountered (we plan to include them in future versions of the system as these species are formally described). Some species, known from limited specimens or unique holotypes, were not available for study via loan and could not be fully scored. Although we have used numerous new characters in this system, not all of them (particularly measurement characters) have been studied in all species, thus the character matrix is not complete. Although males often have useful taxonomic features (particularly in the terminalia) and a few species have notable secondary sexual characters, the taxonomy of Anastrepha and Toxotrypana has been based primarily on females. In many species the male is unknown or has been incompletely described, and within some species groups or among many closely related species the males cannot be distinguished. We have included male characters and images in the system, but the user should be aware that frequently it will be impossible to identify male specimens. The few species that are known only from the male have been included, but some are difficult to identify.

General information

Other useful online electronic resources on fruit flies include interactive identification keys for the adults and larvae of the most important pest species of Tephritidae available at Pest Fruit Flies of the World, and the following databases on the Systematic Entomology Laboratory website: a comprehensive data base of fruit fly names (Norrbom et al. 1999; Norrbom 2004a) much of which is incorporated into Systema Dipterorum (formerly the ‘Biosystematic Database of World Diptera’; a host plant data base for Anastrepha and Toxotrypana (Norrbom 2004b); a specimen data base for New World fruit fly species; and a data base on fruit fly taxonomic literature (updated from Carroll et al. 1999). Also see the Fruit Fly Taxonomy Pages for additional information. After making an identification with the interactive keys, the user may query these databases for complete nomenclatural and distributional data, as well as pertinent references.

Economic Importance

True fruit flies (Diptera: Tephritidae) include some of the world’s most serious agricultural pests. Besides causing billions of dollars in direct losses to a wide variety of fruit, vegetable and flower crops (e.g., citrus, apple, mango, sunflower), they limit the development of agriculture in many countries because of the strict trade quarantines imposed to prevent their spread. Of the more than 4,400 species known worldwide (Norrbom 2004a), nearly 200 are considered pests. Reliable identifications of specimens are critical for effective control programs for pest fruit flies and to regulatory agencies to detect new outbreaks of invasive species. An interactive identification key for the adults and larvae of the most important species is available at Pest Fruit Flies of the World.

Anastrepha includes such major pests as the Mexican fruit fly (A. ludens (Loew)), one of the most important pests of mango, citrus, and other crops in Mexico and Central America, the South American fruit fly complex (A. fraterculus (Wiedemann)), which attacks many crops in South America, the West Indian fruit fly (A. obliqua (Macquart)), one of the most important pests of mango and other crops in the New World, the sapote fruit fly (A. serpentina (Wiedemann)), the Caribbean fruit fly (A. suspensa) (Loew)), the guava fruit fly (A. striata Schiner), the inga fruit fly (A. distincta Greene), and A. sororcula Zucchi, as well as numerous other species of lesser or potential economic significance. Toxotrypana contains at least two species known to attack papaya, including the papaya fruit fly (T. curvicauda Gerstaecker), which is the most economically important species. The pest status of these and other species was reviewed by White & Elson-Harris (1992) and the host plant records for all species of both genera were compiled by Norrbom (2004b). The host and other fruit fly databases also are available online.

Anastrepha and Toxotrypana species breed almost exclusively in fruits, although A. manihoti attacks the terminal buds and shoots of yuca (Peña & Bellotti 1977, Caraballo 1981). Larvae of many species apparently develop in the pulp of the fruit, but others feed exclusively or facultatively on the seeds or developing seed tissues (see Norrbom et al. 1999b). The host range of Anastrepha and Toxotrypana is extremely broad. More than 330 [numbers from 2004, need to be updated] plant species in 48 families have been reported as hosts (not counting records of plants undetermined beyond the genus level). However, less than 200 of them are native plants, and much of the host diversity is due to just a few generalist fly species. For example, if the hosts of the seven most polyphagous species (A. distincta, fraterculus, ludens, obliqua, serpentina, striata, and suspensa) are disregarded, along with the exotic and doubtful or questionable hosts of the other species, only about 110 native host plants in 35 families are known for the remaining Anastrepha and Toxotrypana species. On the other hand, there must be many more unknown native hosts because more than half of the species of Anastrepha and Toxotrypana have no known hosts. Previous collecting has concentrated on commercial fruits, many of which are exotic, and extensive collecting and rearing from native wild plants are needed to gain an understanding of the biologically poorly known species.

Distribution

Both Anastrepha and Toxotrypana are endemic to and widespread in the American tropics and subtropics. Species of both genera occur from the extreme southern United States (the Rio Grande Valley of Texas, southern Florida) to northern Argentina. Both genera are present in the Antilles, although Toxotrypana is absent in the Guianas and Amazonia except bordering the Andes. Neither genus occurs in Chile.

The data and images

The data matrix for this system was compiled in DELTA format. Interactive keys using Intkey and the Lucid Player were generated from these data.

The characters, character dependencies, and data matrix were converted to Lucid 2 Interchange Format (LIF) by means of the Lucid Translator, and imported into Lucid 3.5. The character notes and other DELTA data were imported into Lucid by means of ad hoc programs written by MJD.

Natural-language descriptions were generated from the DELTA data by the program Confor (Dallwitz, Paine, and Zurcher 1993). They are available directly as Web pages, and are also accessible from within the Intkey and Lucid keys. For measurements and ratios the values are estimates of the ranges for these values; actual data follow in parentheses.

The images in this system are from a variety of sources, including the literature. We have attempted, as specimens in good condition were available to be photographed, to provide new color images for each species, including at least the following: female dorsal habitus, wing, eversible membrane (dorsal), aculeus and tip (ventral). For species with unusual markings, we included additional images as appropriate for the head (anterior or lateral), thorax (lateral or posterior), abdomen (dorsal), or habitus (lateral). Line drawings, particularly of the male and female terminalia, have been included where available.

The majority of the color images were taken with a Visionary Digital system. They were montaged with HeliconFocus or CombineZP and enhanced using Adobe Photoshop. The habitus images are idealized illustrations rather than simple photographs. We have modified them to look as much as possible like a fly with all of its parts visible in the same position. Each is a composite of at least five separate images (head, thorax, abdomen, oviscape, and wing), each positioned so that it is level. These were then combined using Adobe Photoshop. Eye color and legs were added from a template; the latter were not taken for each specimen as, other than color, the legs have little taxonomic importance within Anastrepha. Color and exposure were adjusted to match the original specimen. Major setae were often repainted to try and match their actual color (and replace any missing setae); they frequently suffered color aberration or were not fully in focus in the original images. Minor damage was repaired and/or debris removed by the Clone Stamp Tool.

The interactive keys

The Intkey key runs under MS Windows 95/NT or later, and will also run on Macintosh and Linux computers with Windows emulation software. The Lucid3 keys require the Java Runtime Environment Version 1.5 or later which is available for computers running Windows, Solaris, Linux, and Apple OS X.

We have assumed that our users are professionals, such as identifiers working for USDA APHIS-PPQ, who are already familiar with traditional identification aids and keys, and have some knowledge of fruit fly identification. However, all but the most basic morphological terms used in the system can be found in the Morphology section and on the Help pages associated with the characters.

An interactive key differs from traditional identification tools in allowing for random access to character data. The user is free to choose any of the available characters in any order, whereas a traditional key allows only for the use of specific characters in a rigid sequence. The program can select the best characters for use, based on their ability to separate the remaining taxa under consideration. For a detailed example of interactive identification, see An Intkey Example: Identification. (The process is similar in other programs, but they may lack some of the features of Intkey.)

The verification process is also much easier. Complete descriptions are available, just as in traditional taxonomic publications. Intkey can also indicate the differences between the specimen and a taxon, or within any set of taxa, and can generate diagnostic descriptions of taxa.

The programs can accommodate errors (e.g., a poor or aberrant specimen, a mistake by the user, or an error in the database). Numeric characters and characters with more than two states are allowed. This speeds up the identification process by reducing the total number of decisions that must be made, because more than the traditional two possibilities can be efficiently evaluated at one time. Characters are accompanied by illustrations and notes that can be accessed at any time.

The user should be aware, of course, that interactive keys are not a panacea. Unusual specimens, those outside the domain of the data or with distorted features will still have to be sent to the systematist. See Principles of interactive keys for additional explanation of the features and advantages of interactive keys in general, and Comparison of interactive identification programs for comparisons of various interactive-key programs. (The latter publication refers to an earlier version of Lucid; an update is in preparation.)