Silba adipata McAlpine

Presentation      Biology      Living habits      Infestation      Control methods

 


Home > Presentation > Wing venation.

 

Author: François DROUET.
Photographs: François DROUET.
(unless indicated).
All rights reserved.

 

 

Wing venation

 

 

 

According to the following plan: using wing venation in the identification process, my observations, other observers.

 

USING WING VENATION IN THE IDENTIFICATION PROCESS

 

It should be emphasized that, being common to all genera and species of the Lonchaeidae family, the wing venation does not identify Silba adipata McAlpine. But the configuration of the wing anterior edge can be used in the identification process of Silba adipata McAlpine to rule out lookalike species which would present a different configuration. The presence of the wing anterior edge configuration of the Lonchaeidae family is a necessary (but not sufficient) condition, which must imperatively be verified during the identification process of Silba adipata McAlpine.

In practice, in my identification process, I first check the following criteria: body color and shine, size, absence of spots on the wings, translucent nature of the wings (which must not be smoked), wings position at rest. If the individual to be identified satisfies these criteria, I check the venation of the wing anterior edge to eliminate lookalike species that do not belong to the Lonchaeidae family.

Then, I take into account (when possible on the photographs...) another series of criteria: length of the folded wings in relation to the body, interocular space width, absence of setae on the prescutum, as well as on the anterior and central parts of the scutum, poorly developed villus on the anterior part of the head, hairiness of the abdomen (which must be short). When the photographs are close-up, I lastly focus on the position and number of setae on the top of the head, and on the posterior part of the scutum and scutellum.
 

 Silba adipata McAlpine: wing venation.

 Silba adipata McAlpine: wing venation.
(note in particular, on the right wing, the anterior edge venation specific to the Lonchaeidae family).

 

MY OBSERVATIONS

 

USED PROCESS

To observe the wing venation, it is necessary to use a strong magnifier and examine the deployed wing flat on the surface of the liquid contained in the trap. The venation is not always visible because the attractant liquid is cloudy. Moreover, a certain number of individuals are no longer on the surface, but at the bottom of the trap.

In case of doubt (quite frequent), I remove the individuals from the trap with dissection tweezers to examine them. But, in most cases, when the fly is removed from the liquid in the trap, the wet wings curl up on themselves lengthwise and stick to the body, making it impossible to examine their venation.

I place the wet flies for a few moments on kitchen paper to rid them of most of the water of which they are loaded, especially on the wings. When the flies are practically dry, I gently place them on the surface of the water contained in a flat cup. At least one wing then gradually unfolds flat, and I can orient the body with the dissection tweezers to obtain the angle of examination under the magnifying glass, then the angle of photography, that I wish.
 

Two flies on the water surface, in a flat cup, for wing venation observation.

Two flies on the water surface, in a flat cup, for wing venation observation.

 

BLACK FIG FLY 'S WING VENATION

In the Black Fig Fly photograph below, focusing on the left wing, we note that the venation of the wing anterior edge is that of the Lonchaeidae family, to which this species belongs: the subcosta (Sc) runs very closely and almost in parallel with the radius (R1), and joins the costa (C) a little forward than R1 seems to do. In fact, R1 dives towards C without touching it and follows it very closely, gradually approaching to die far enough from the point of junction of Sc with C..
 

Silba adipata McAlpine : venation of the wing anterior edge.

 Silba adipata McAlpine: venation of the wing anterior edge.

 

Silba adipata McAlpine : venation of the wing anterior edge.

Silba adipata McAlpine: venation of the wing anterior edge.
 

The Silba adipata McAlpine photograph below shows a costal break just before the junction of the subscosta and the costa, with the presence of a spine more long than the spinules which border the costa.

Black Fig Fly: costal break just before the junction of the subscosta and the costa.

Black Fig Fly: costal break just before the junction of the subscosta and the costa, with the presence of a spine.
(at the top, on the right, in the photograph).
 

I have noticed that on photographs taken from afar, the subcosta and the radius appear to form a single line and the area of their junction with the costa seems to be a triangle at the end of the costal cell (photograph below).
 

Black Fig Fly: wing anterior edge venation, seen from afar

Black Fig Fly: wing anterior edge venation, seen from afar.
(note the two elongated ovals, followed by two small triangles, at the beginning of the wings).

 

OTHER OBSERVERS

 

OBSERVATIONS OF FABIAN COUSINIÉ

Fabian COUSINIÉ, who did a professional internship at CIVAMBIO 66 in 2017 (with the subject of Silba adipata McAlpine mass trapping) sent me the following photographs of the wing taken under a stereomicroscope.
 

Black Fig Fly: wing venation.

Black Fig Fly: wing venation.
Credit:
Fabian COUSINIÉ,
CIVAMBIO 66.

 

Black Fig Fly: wing anterior edge venation.

Black Fig Fly: wing anterior edge venation.
(note that the subcosta and the radius are parallel and very close to each other).
Credit: Fabian COUSINIÉ,
CIVAMBIO 66.
 

The photograph below shows the costal break just before the junction of the subscosta and the costa, with the presence of a spine more long than the spinules which border the costa.
 

Black Fig Fly: costal break just before the junction of the subscosta and the costa.

Black Fig Fly: costal break just before the junction of the subscosta and the costa, with the presence of a spine.
 Credit:
Fabian COUSINIÉ,
CIVAMBIO 66.

 

OBSERVATIONS OF FILIPPO SILVESTRI

Filippo SILVESTRI does not detail the wing venation in his masterful study relating to the Black Fig Fly. But he provides two very precise line drawings, reproduced below, which show that my observations of the venation of the wing anterior edge agree with his. Reference: SILVESTRI F. - Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, 1917, vol.12, pp. 123 -146.
 

Black Fig Fly female.

Black Fig Fly female (note the wing venation).
Credit:
F. SILVESTRI.

 

Black Fig Fly's wing nervation.

Black Fig Fly's wing nervation.
Credit:
F. SILVESTRI.

 

OBSERVATIONS OF EUGÈNE SÉGUY

Eugène SÉGUY describes Silba adipata McAlpine under the name of Lonchaea aristella Beck. as did Filippo SILVESTRI, whom he quotes and whose certain figures he reproduces. Reference: SÉGUY E. - Diptères (Brachycères), Faune de France, vol. 28, page 176, Paul LECHEVALIER et fils, Paris, 1934.

On page 171 of the book, the configuration of the wing anterior edge observed in Silba adipata McAlpine is described and mentioned by the author as one of the characteristics of the Lonchaeidae family (to which Silba adipata McAlpine belongs). On page 34, the author indicates another characteristic of the wing venation for the Lonchaeidae family: first anal vein thickened at the base and second anal vein always present.

I do not use the characteristics of anal nervation mentioned by Eugène SÉGUY; they bring nothing about the species, and the family is already determined by the configuration of the wing anterior edge. In addition, the wing anal venation very hardly appears on the photographs, and most often incomplete. It is better to exploit it under a stereomicroscope.

I do not detail the other identification criteria provided on pages 171, 172 and 176 by Eugène SÉGUY for the Lonchaeidae family, the Lonchaea genus, and the Lonchaea aristella Beck. species (name he attributed to Silba adipata McAlpine). They are only visible under a stereomicroscope, and with a trained eye. Knowing that in any case the strict determination of the species could only be obtained by examining the male genitalia.

On page 33, the author provides a drawing of the wing venation for the genus Lonchaea, which I reproduce below. I note that the author marks with an arrow the location of the costal break, and highlights the first and second anal veins.

Wing nervation of the Lonchaea genus.

Wing nervation of the Lonchaea genus.
 
Credit: Eugène SÉGUY.

 

 

Top of the page. Top of page   Back to summary. Summary