Presentation Biology Living habits Infestation Control methods
Author : François DROUET.
Photographs : François DROUET.
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Mating place
I provide below some information and reflections relative to the potential mating place of the Silba adipata McAlpine species, putting forward a plausible hypothesis. I supplement these with the observation that no mating occurs under laboratory conditions.
WHERE DOES SILBA ADIPATA McALPINE MATING TAKE PLACE ?
A PLAUSIBLE HYPOTHESIS
In my many years of intensive observations of Silba adipata McAlpine on various fig trees, at all periods of the season and at any times of the day, I was able once only to see two mated flies of this species. I am therefore convinced that Silba adipata McAlpine mating does not occur on fig trees, and that mated flies of this species only very rarely land on these.
My conviction is reinforced by the responses of the three other main contributors to this website, all experienced Silba adipata McAlpine observers, whom I asked if they had ever observed mating for this species. Alain COSTA (agricultural engineer, consultant and fig producer in Spain) and Bernard PEYRE (consultant trainer for the French fig industry) have only once observed two black fig flies mated on a fig tree, without witnessing the mating phase (like myself). B. PEYRE is the only one of the three of us having seen the mated black fig flies in flight, just before they landed on a fig tree leaf (see chapter reporting this observation). Margaux ALLIX (in charge of technical support within the CIVAMBIO 66 producers group) has never observed mated black fig flies.
I have not found in the specialized literature any information on the mating place of the Black Fig Fly (2026). I note in particular that F. SILVESTRI provides no information relating to mating in his masterful study of the Black Fig Fly. Reference: SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146.
And B. I. KATSOYANNOS, who studied in 1981 and 1982 large populations of black fig flies in the island of Chios (Greece), explicitly states that he has not observed any mating in the field, nor in the laboratory. Reference: KATSOYANNOS B. I., 1983, Field observations on the biology and behavior of the black fig fly Silba adipata McAlpine (Diptera, Lonchaeidae), and trapping experiments, Z. ang. Entomol. 95, pp. 471-476.
For me, it follows from the above considerations that a plausible hypothesis is that Silba adipata McAlpine mating occurs during flight. This hypothesis is supported by the relationship between mating and aerial swarming presented in the sub-chapter below (altough it does not agree with the conclusion of McALPINE and MUNROE appearing in the sub-chapter).
RELATIONSHIP WITH AERIAL SWARMING
In insects, aerial swarms are generally associated with mating activity, characterized by pair formation in flight. Numerous references, among which I cite: SULLIVAN Robert T., 1981, Insect Swarming and Mating, The Florida Entomologist, vol. 64 (1), pp. 44–65.
I only know one reported swarm observation for Silba adipata McAlpine. It was made on August 20, 1982 by B. I. KATSOYANNOS, while he was studying Lamprolonchaea smaragdi Walker swarming in the Chios Island (Greece). He specifies that the swarm consisted of approximately 20 individuals, and that among the eight individuals he was able to capture in a net was one female. Reference: KATSOYANNOS B. I., 1983, Swarming of Lamprolonchaea smaragdi Walker (Diptera, Lonchaeidae) and a few other Diptera observed in Chios, Greece, Bulletin de la Société Entomologique Suisse, vol. 56, pp. 183 -185.
J. F. McALPINE and D. D. MUNROE have described the swarming behavior for sixteen species of the Lonchaeidae family (which do not include Siba adipata McAlpine). Reference: McALPINE J. F., MUNROE D. D., 1968, Swarming on Lonchaeid flies and others insects, with description of four new species of Lonchaeidae (Diptera), The CanadianEntomologist, vol.100, pp. 1154-1178.
I note that the aerial swarms of these species were all observed at heights between 0.30 m and 2.10 m. For the authors, swarming is traditionally associated with mating, but while most observers agree that these are two sequentially coordinated activities, the degree to which they are linked is the subject of considerable debate. On this topic, the authors provide numerous bibliographic references, from which they retain the following principles.
Swarming is independent of the females presence, but the fact that the swarming onset so often coincides with sexual maturity seems to indicate that it is endogenously linked to sexual factors. Swarming and mating are two independent, though coordinated, behavioral processes. Swarming responds to visual stimuli from markers at relatively long distances, while mating is governed by a proximity mechanism in response to tactile stimuli. An individual within a swarm ceases to belong to it as soon as its courtship and short-distance mating mechanisms are activated - that is, as soon as it approaches and makes contact with a potential mate - and it only rejoins the swarm after dissociating from that mate. The mating process occurs once the mates have landed.
The authors validate these principles for the Lonchaeidae family based, in fact, on limited personal observations: females are rarely found in swarms of Lonchaeidae individuals, mating has never been observed within them, and a pair of Lonchaea laxa was seen copulating on a leaf near the swarming site.
MY OBSERVATIONS
I have no personal observation of Silba adipata McAlpine aerial swarms. Nevertheless, I regularly observe black fig flies groups flying between two trees in a similar way than that of the swarm described by B. I. KATSOYANNOS. I do not qualify them as aerial swarms because these groups only involve two to three specimens. The group performs repetitive flights, more or less on the horizontal plane and limited to an elliptic space, with an amplitude of about 2 m, at a height of about 1.5 m. The aerial group is rather stationary, but inside the group the flies permanently keep their very fast zigzaging characteristic flight pattern.
I can observe this phenomenon for long whiles, sometimes more than one hour, in the late afternoon, at dusk. Over the season, I regularly perform this type of observations at two places: between my ‘Bellone’ variety fig tree and an oriental persimmon (in June), and between an olive tree and a silky oak, near a hedge, at 30 m from my fig trees (during certain periods of summer). I think that these black fig flies grouped in the air are males waiting for females, or males and females just before mating (or mating).
ABSENCE OF MATING UNDER LABORATORY CONDITIONS
Several observers report the absence of mating under laboratory conditions for the Silba adipata McAlpine species (see observations below). To explain the absence of mating, I propose the hypothesis that the living conditions in the laboratory do not allow Silba adipata McAlpine to form aerial swarms (if these truly condition the possibilities of mating in flight for the species).
Observation 1.
B. I. KATSOYANNOS, who studied large populations of black fig flies on the island of Chios (Greece) in 1981 and 1982, attempted to observe mating behavior of Silba adipata McAlpine in the laboratory. Reference: KATSOYANNOS B. I., 1983, Field observations on the biology and behavior of the black fig fly Silba adipata McAlpine (Diptera, Lonchaeidae), and trapping experiments, Z. ang. Entomol. 95, pp. 471-476.
The author kept the flies that emerged from the pupae in the laboratory in groups of 20 to 50 individuals of both sexes in 30 x 30 x 30 cm cages at 25 °C, with 60–70% relative humidity and natural light from the room's windows. The cages were provided with water and food (yeast hydrolysate, water, and sugar in a 1:4:5 ratio). B. I. KATSOYANNOS also placed unripe figs in them for oviposition.
He reports that of the 2,000 eggs laid in the unripe figs placed in the cages, none hatched, suggesting that none of the females that laid eggs had mated. This observation is supported by the fact that he did not observe any mating in the laboratory. B. I. KATSOYANNOS tried to encourage mating by placing fig branches and leaves in the cages in addition to the unripe figs, but without success.
Observation 2.
In 2024, PANIAGUA-JASSO E. et al. published in the journal Insects an article relative to the bioecological parameters of the Silba adipata McAlpine species. Reference: PANIAGUA-JASSO E., TEJEDA-REYES M.A., MARTINEZ-CASTILLO A.M., FIGUEROA-DE LA ROSA J.I., GARCIA-BANDERAS D.V., PALMA-CASTILLO L.J., ILLESCAS-RIQUELME C.P., PINEDA-GUILLERMO S., 2024, Bioecological parameters of the Black Fig Fly, Silba adipata (Diptera: Lonchaeidae), collected from fig crops in Mexico, Insects 15, no. 11: 883. The authors report that, during preliminary tests, they collected 30 eggs from one of four figs that had been exposed in the laboratory to Silba adipata McAlpine females for oviposition; however, none of these eggs hatched. They hypothesize that this was due to the absence of mating, citing the aforementioned observations by B. I. KATSOYANNOS.
Observation 3.
In 2025, DIAZ-DEL-CASTILLO R. et al. published in the journal Insects an article relative to the sexual development of the Silba adipata McAlpine species. Reference: DIAZ-DEL-CASTILLO R., CÓRDOVA-GARCIA G., PÉREZ-STAPLES D., BIRKE A., WILLIAMS T., LASA R., 2025, Sexual Development of Silba adipata (Diptera: Lonchaeidae): Effects of Diet, Ultraviolet Light and Fig Latex, Insects 16, no. 5: 495. The authors state that they did not observe any mating, even though males were placed in the same cages as mature females aged 15 to 27 days. They refer to the aforementioned observations by B. I. KATSOYANNOS and suggest that the unsuccessful attempts to breed the species Silba adipata McAlpine in the laboratory might be explained by the inability to meet the specific conditions required for the formation of males swarms.
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