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Fruit Fly (Diptera: Tephritidae) Recognition
The shape of the subcosta (bent sharply forward subapically and usually weaker or foldlike beyond the bend) has generally been considered the best diagnositic character for adult fruit flies, but its form varies and in some taxa, especially many species with elongate wings, it is not as sharply bent (e.g., Toxotrypana, many Phytalmiini), and in species of Tachiniscinae it is not as weak distal to the bend. Some Plastotephritinae (Platystomatidae), various Pyrgotidae, and a few other species of Tephritoidea also have a similarly shaped, strongly bent subcosta, although these lack distinct frontal bristles, which within the Tephritoidea are present only in Tephritidae (including Tachiniscinae) and some Ulidiidae.
Although the above characters will distinguish most adult tephritids from most other flies, the following list of characters is more reliable for their diagnosis: Length 1 to 35 mm. Body variously colored but nonmetallic (except several metallic blue Trirhithrum and Adramini spp. from Madagascar, bluish Bibundia spp. from Africa, and Tachinisca cyaneiventris from South America, which has a purplish abdomen). Frons with both inclinate frontal bristles (sometimes reduced or absent in wasp mimics such as Monacrostichus, Pseudophorellia, or Toxotrypana) and 1-2 (rarely 3) orbital bristles; ocelli present; anepisternum with vertical suture on posterior third (difficult to see in densely microtrichose species); anepimeron with at least one seta medially and with greater ampulla usually well developed; wing usually patterned; costa with humeral and subcostal breaks; subcosta bent sharply forward subapically and usually weaker or foldlike beyond the bend (except some Phytalmiini); vein R1 densely setulose dorsally almost to base; cell bcu usually with at least a small posteroapical extension due to bend in vein Cu2 (except in Myopitini and a few other taxa); female with ovipositor of piercing type, including a strongly sclerotized aculeus that telescopes into fused oviscape; and male with correspondingly long, coiled phallus, stored between genitalia and tergite 5 at rest and bearing a stout apical glans (absent in some Anastrepha).
No diagnoses or keys have been produced to distinguish tephritid eggs from those of other families of Diptera. They are 0.35-1.65 mm long, white to pale brown, elongate-oval to pedicillate, often slightly curved, and smooth to rugose-textured, often with raised areas in hexagonal or similar shapes. The anterior, apical to subapical micropyle is usually noticeable (Ferrar 1987). Some species have a slender lobe, sometimes extremely elongate, on the anterior end. Tephritid eggs have a well-developed chorionic respiratory system with aeropyles confined to the anterior pole, and lack a plastron (Hinton 1981). Hatching lines are absent, hatching being accomplished by the rasping of the larval mandibles and by the pressure of the larva turning within the egg.
Fruit fly larvae and puparia are typically muscomorph and are recognized by the lack of a sclerotized peritreme surrounding the posterior spiracles, which are not elevated off the surface of the caudal segment (B.A. Foote 1991). Ferrar (1987) provided descriptions of these stages. The larvae are white to yellow, seldom with darker caudal or ventral areas. In most species they are elongate cylindrical, but in gall and flower-breeding taxa they may be stout and subspherical. They are metapneustic as first instars and amphipneustic as second and third instars. Rudiments of spiracles on the intervening segments are evidently generally present (Headrick & Goeden 1991, 1993, Goeden & Headrick 1992, Carroll 1992), but have not been proven functional. First instars of all fruit fly species, and all instars of the species of Myopites so far studied, have only two posterior spiracular slits (Freidberg 1980). In other third instars (and puparia), the three posterior spiracular slits are straight, and they are oriented radially from the ecdysial scar, subparallel to perpendicular to one another. In frugivorous species the angle between the dorsal and ventral slits is usually no more than 90 degrees (B.A. Foote 1991), but it is greater insome species of Tephritinae. The anterior spiracles are sessile or nearly so, and usually fan-shaped or bimodal, with 2-53 papillae (Ferrar 1987). The cephalopharyngeal skeletons of all species so far described are typically muscomorph, with right and left mandibles equally developed, and sometimes with 1-2 subapical teeth persisting into the third instar (as far as known, subapical teeth are always well-developed in earlier instars). Fruit fly puparia are usually barrel-shaped, but rarely are bean-shaped or have a flattened caudal segment. They may be smooth or wrinkled, with distinct or unclear segmentation. They range in color from white to yellow, brown or black, and their color may vary from the anterior to the posterior end.
See the Fruit Fly Bibliography Database for full information for cited references.
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Content by Allen L. Norrbom. Last Updated: November 10, 2004.