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  • University of Thessaloniki, Faculty of Agriculture, Laboratory of Applied Zoology and Parasitology, Thessaloniki, Greece

    Field observations on the biology and behavior of the black fig fly Silba adipata McAlpine (Diptera, Lonchaeidae),

    and trapping experiments

    By B. I. KATSOYANNOS

    Abstract Large populations of the black fig fly, Silba adipata McAl ine, previously misidentified as Lonchaea (Carpolonchaea) aristella Becker, were observed on [g trees in Chios, Greece. O n fig trees flies fed mostly during the morning and late afternoon hours, predominantly on sweet exudates from ripe figs and on fresh or dry milky fig-tree sap exuded from injuried plant parts. The odor of this sap attracted the flies. Oviposition always took place in the eye of unripe figs, mostly during the afternoon hours until dark. As many as 63 S. udiputu pupae were obtained from a single unripe fig. A parasite, Pachycwpoidegs vindemmiue Rondani (Hym., Pteromalidae), emerged from S. adipata pupae. McPhail traps baited with 2 % ammonium sulfate or 0.5 to 1 ml fresh fig- tree sap were attractive for the flies. Sticky, yellow traps were not effective.

    1 Introduction

    According to earlier workers, the black fig fly, Silba adipata McAlpine (often misidentified as Lonchaea [Carpolonchaea, Silba] aristella Becker), (Dipt., Lonchaeidae), is a serious pest of figs in the Mediterranean basin and Middle East countries as far as Iraq (SILVESTRI 1917; ANAGNOSTOPOULOS 1939; TALHOUK 1969). It is a multivoltine (4-6 generations per year), apparently monophagous species; the female oviposit exclusively in cultivated and wild figs which serve as the larval food.

    In September 1981, I detected large populations of lonchaeid flies resting, feeding or ovipositing on figs, in the island of Chios, Greece. Samples of these flies, captured in traps or bred from infested figs, were identified by Dr. J. E. MCALPINE, Biosystematics Research Institute, Ottawa, Canada, as Silba adipata McAlpine. Flies of the same species were also obtained from pupae originating from infested wild figs collected in October 1981 in Thessaloniki (Northern Greece).

    According to McAlpine, S. adipata is the same species as Lonchaea (Car- polonchaea, Silba) aristella, studied by SILVESTRI (1917), i.e. SILVESTRI mis- identified his specimens. Silba aristella is a junior synonym of s. virescens Maquart which has been reared on several occasions from shoots, stalks and ears of corn, the sole known host (MCALPINE, pers. commun.). Thus, previous reports (CZERNY 1934; SCHEWKET 1934; %GUY 1934; ANAGNOSTOPOULOS 1939; TALHOUK 1969), based on SILVESTRIS study and referring to the black

    US. Copyright Clearance Center Code Statement: 0044-2240/83/9505-0471 $ 02.50/0 Z. ang. Ent. 95 (1983), 471-476 0 1983 Verlag Paul Parey, Hamburg und Berlin ISSN 0044-2240 / Intercode: ZANEAE

  • 472 B. I . Katsoyannos

    fig fly as Lonchaea or Carpolonchaea aristella, were in fact dealing with S. adipata.

    Here, I report observations concerning the biology and behavior of this fly and its responses to some odor and color traps.

    2 Materials and methods

    The observations were made during September 1981 and also in August and September 1982, in Chios, Greece, on a farm producing mainly citrus fruits and vegetables. In and around the cultivated area and in the proximity of the farm-buildings, there were also other species of trees including several fig trees.

    Direct observations on the behavior of S. adimta were made on 3 large fig trees of different local varieties. The trees were ca. 10 m high and '10-15 m in canopy diamgter,\ith branches and foliage extending to the ground. They bore fruits in all stages of maturity, most being immature. The observations were made at intervals from early morning until dark. They consisted of watching flies located on various plant parts for as long as remained in view, from some seconds to 30 minutes and recording their location and activities. The presence of the observer, as long as he remained at a distance of half a meter or more from the flies, apparently did not influence their normal behavior.

    Figs in various stages of maturity were picked on several occasions and taken to the laboratory to determine the degree of infestation. Flies that emerged from field-collected pupae were kept in groups of ca. 20-50 individuals of both sexes in 30 x 30 x 30 cm cages under 25 "C and 60-70 '70 RH, with daylight entering from the room windows, and were provided with water, fdod (yeast hydrolysate, water and sugar in proportion 1 :4 :5) and unripe figs for oviposition.

    Tra ping experiments were conducted on 6 fig trees variously spaced from 10 to 200 m, using

    sulfate or a small quantity, (10 drops or 0.5 to 1 ml), of fresh milky fig-tree sap dissolved in water or poured over a piece of cotton suspended into the trap containing water. Tree sap is easily collected by cutting leaves or unripe figs and letting the few drops formed at each cut fall into a bottle or directly into the trap. McPhail traps containing only water served as a check. Usually 4-8 traps, 1-2 of each treatment, were suspended per tree for 2-5 days. The position of the traps was daily rotated.

    Rebell cit yellow sticky traps and McPhail traps baited with 2 % aqueous solution of ammonium

    3 Results and discussion 3.1 Feeding behavior

    Observations on more than 200 flies revealed that S. adipata adults fed predominantly during the early morning, as soon as the temperature increased above 18 "C and also from late afternoon until dark. In most cases, the flies fed on sweet fig juice exuding from overripe figs which remained hanging on the trees. Although two or more flies were frequently observed feeding at the same point, one almost touching the other, there was no indication of aggressive behavior between those flies. Flies were also frequently observed feeding on drops of fresh or dry milky fig-tree sap exuded when unripe fruits or leaves were removed from the tree or where unripe figs or leaves had been injured by insects, friction or other causes. Fresh milky fig-tree sap was strongly attractive to the flies. On one occasion, I observed an aggregation of 7 flies feeding upon a drop coming from a fresh scar of a leaf I had removed a few minutes earlier. After this accidental observation, I repeated the process several times by removing leaves or unripe figs. Almost always, within a few minutes, several flies approached by a zig-zag flight pattern, landed near the wound from which sap was being exuded and began to feed on it. That this attraction is due to a humidity gradient from the fresh sap rather than to fig-tree sap odor is unlikely because many water sources were available in the vicinity. Further- more, flies were frequently observed feeding on wounds made the previous

  • Field observations on biology and behavior of S. adipata 473

    day, where the sap had already dried up. It is noteworthy that the response of the flies to the fig-tree sap was so marked and frequent that causing sap to exude, could be a useful and rapid method for detecting S. udiputu flies on fig trees.

    Exudates from ripe figs are probably the main adult food when ripe figs are available. However, before fig maturity, other food sources including milky fig-tree sap serve as food for the flies. Before mature figs were available in the area, in August 1982 I often observed flies feeding upon or inside the flowers of an ornamental creeping plant, the trumpet-creeper, Cumpsis (Tecornu) rudicuns Juss (Bingoniacae), located ca. 50 m away from the fig trees. During the same period S. udiputu flies were also observed on citrus and olive trees of the area. These observations indicate that S. udiputu flies exhibit foraging behavior.

    TALHOUK (1969), referring to previous literature concerning L. uristellu which he believed was the black fig fly, reported that the adults feed on exudates of the fig wax scale, Ceroplustes rusci L., and other insects, as well as on juice from ripe figs later in the season.

    3.2 Mating behavior

    No mating activity by S. udiputu was observed in the field or in the laboratory where flies from field-collected pupae were kept in cages. More than 2000 eggs deposited by females of these flies in unripe figs offered to them as oviposition sites failed to hatch; this suggests that these females were unmated. The presence of unripe figs, shoots or fig leaves placed in the cages holding the flies failed to elicit mating behavior.

    Information concerning the mating behavior of lonchaeids is not available in the literature, except for a few cases of pairs observed in copulation. The well-documented swarming behavior exhibited by many lonchaeid species (MCALPINE and MUNROE 1968) including S. udiputa (KATSOYANNOS, unpubl.), may be of some importance for the mating of this species.

    3.3 Oviposition behavior and fruit infestation

    Although females were observed ovipositing throughout the day except early morning, oviposition most occurred during the afternoon and until dark. In all cases observed, the eggs were laid in the eye of unripe figs, preferably those in shade at the time.

    Following a zig-zag flight, each female landed upon the fig and in a short time, in most cases within some seconds, it located the fig eye and began to insert its ovipositor between the scales surrounding the eye. After some ovipositor-pushing movements presumably followed by oviposition, the female changed position by walking over the eye and took up new position for further egg laying in the same fruit. The direction of the new position was usually at an angle between 90 to 180" in relation to the previous one. This behavior of changing position followed by further egg laying in the same fruit was repeated by each female several times; the maximum count

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