The Back Fig Fly is difficult to see on a fig tree. For detecting it, I use means based on its incredible avidity for the fig tree latex (which is not the sap).

 

TEARING A FIG TREE LEAF FROM THE BRANCH

Choose a peripheral leaf (as big as possible) in the shaded or partially shaded part of the fig tree, at a height of 1 to 1.50 m (to well see the result), and tear the leaf from the twig. You will observe on the twig a large latex influx at the place where the petiole was attached. There is also latex oozing at the end of the torn petiole. Spread this latex along the twig below the latex influx, using the petiole as a paintbruh. Then stays at 2 m from the fig tree to observe the result.

If there are black fig flies on the fig tree, the first of them will land beside the latex influx after 30 seconds to a few minutes. If after a quarter of an hour, you have not yet seen flies, be sure that there are currently no black fig flies on the fig tree. But they may arrive one or two hours after, and they will be immediately attracted by the latex influx place, even if the latex has partially dried. The latex will remain attractive for the black fig flies the next two days, but less and less along the time.

Note that, according to my experience, there is no another fly or insect wich could be attracted by the latex influx at the base of a torn fig tree leaf petiole. I saw the Mediterranean Fruit Fly (Ceratitis capitata Wiedemann) sometimes briefly sucking fig tree latex, but only the one oozing out of its egg laying holes in the fig epidermis.
 

A black fig fly consuming fig tree latex (base of a torn fig tree leaf petiole).
 

Once a black fig fly is absorbed in its latex sucking task, if you avoid sudden movements, you can approach the camera up to 2 cm from the fly.
 

A black fig fly consuming fig tree latex (base of a torn fig tree leaf petiole).
 

There is usually from 1 to 3 black fig flies on the fig tree, at certain periods 4 to 5, very rarely 6 to 8. I observe in my orchard that the black fig flies frequent more intensely the fig tree for feeding activities in early morning and in late evening. Using the detection mean at these periods of the day increases the chances to see black fig flies, but it can often be used successfully regardless of the time of day. And using it every two hours from dawn to night permits to know the distribution during the day of the black fig flies presence.

 

A VERY EFFICIENT VARIANT

Instead of tearing the leaf from the twig, cut its petiole at about a 3 cm length. Spread along the cut petiole the latex oozing at the end of the detached part of the petiole.
 

A black fig fly consuming fig tree latex (cut petiole of a fig tree leaf).

 

Black fig flies consuming fig tree latex (cut petiole of a fig tree leaf).

 

DETECTING THE BLACK FIG FLY ON A FIG TREE WHEN THE LEAVES ARE NOT YET DEVELOPED

Debarking a fig tree branch one year or older (grey wood of all sizes) is a method of detecting the presence of Silba adipata McAlpine. It is particularly useful at the very beginning of spring, when the foliage is poorly developed, thus the leaves cannot be torn, or their petiole cut, to cause a latex influx. Debarking causes latex exudation which, although faint and not visible, gives off a distinctly smelling odor and attracts Silba adipata McAlpine if it is on the fig tree.

Careful observation of Silba adipata McAlpine on a debarked fig tree branch reveals a particular behavior : it spends a large part of its time sucking the narrow greenish strip separating the bark from the sapwood, and visible all along the perimeter of the debarked area. This is the bast zone, in which the concentric rings of laticiferous vessels (containing the latex) are located, in addition to the sieve tubes conveying the sap which results from photosynthesis carried out in the leaves. This Silba adipata McAlpine behavior is the same as that observed when it is attracted to a pruning wound of a fig tree branch.
 

A black fig fly attracted to a debarked fig tree branch.

 

A black fig fly sucking the bast zone on a debarked fig tree branch.

 

DETECTING THE BLACK FIG FLY ON A FIG TREE USING AN INFESTED FIG

While breaking unripe attacked figs during my larvae searches, I noticed that their inside is sticky and that after the operation a strong latex smell remains on the fingers. I then had the idea of laying bare the inside of infested unripe figs without detaching them from the branch, by making a double cut with the secateurs (one vertical and one horizontal). I have observed that this method is attractive for the Black Fig Fly, but less than tearing a fig tree leaf (which provides a much larger and more concentrated quantity of latex). Below, two photographs of a black fig fly attracted to a reddened small unripe infested fig left on the tree with the inside laid bare.
 

A black fig fly sucking the whitish parenchyma of an infested fig with the inside laid bare.

 

A black fig fly sucking the whitish parenchyma of an infested fig with the inside laid bare.