Silba adipata McAlpine

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

 

 

The pupa

 

 

 

After staying in the fig central cavity, the Silba adipata McAlpine larva leaves it to dig a gallery in the thickness of the whitish parenchyma, under the epidermis. When it has completed its development, it pierces a hole in the skin to get out of the fig. Then It lets herself fall to the ground and buries itself to turn into a pupa.

 

PUPATION (NYMPHOSIS)

 

Inside the pupa, the larva turns into a fly: this is the pupation (nymphosis). During my experiments in obtaining adult black fig flies, I noticed in July and August a pupation period of 10 days, sometimes 9. And I observed that most often the first individuals emerging from pupae were males.

According to the F. SILVESTRI observations (Napoli region, Italy), the pupation duration  is from 9 to 16 days according to the seasons: 10 days in May, 9-10 days in August, 16 days at the end of October and early November. 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.

It sometimes happens that the pupation takes place inside the fig, and even that the pupation can reach its term there, thus causing the emergence of an imago within the infructescence (which does not survive because it does not manage to get out of the fig...).
 

Some Black Fig Fly pupae.

Some Black Fig Fly pupae.

 

Three Black Fig Fly pupae.

Three Black Fig Fly pupae.

 

PUPA DESCRIPTION

 

The Silba adipata McAlpine pupa is elongated ovoid, reddish brown, with well marked segments. The anterior part is a little narrower than the posterior part. The dorsal part is clearly convex, the ventral part a little less. I observe at the posterior end of the pupa the two stigmata visible on the mobile larva, and at the anterior end the two stigmata less visible on the mobile larva.
 

Silba adipata McAlpine pupa.

Silba adipata McAlpine pupa.
 

The Black Fig Fly pupa changes color as the nymph develops (first whitish, than light brown, and dark brown when the nymph is almost completly developed).
 

Black Fig Fly (Silba adipata McAlpine) : pupa color evolution.

Silba adipata McAlpine: pupa color evolution.
 

The size of the pupae that I have observed is about 4 mm long and 1.8 mm wide. Some were a little smaller.
 

Black Fig Fly pupa size (4 mm long).

Black Fig Fly pupa size (4 mm long).

 

Black Fig Fly (Silba adipata McAlpine) : pupa size (4 mm long).

Black Fig Fly pupa size (4 mm long).

 

PUPA OPENING

 

The pupa opens under the push of the imago ptilinum. The opening is made according to preformed dehiscence lines delimiting a cap which opens like a cover. Below, two photograhs showing  empty pupae found in the soil.
 

Black Fig Fly (Silba adipata McAlpine) : empty pupa found in the soil.

Silba adipata McAlpine: empty pupa found in the soil.

 

Black Fig Fly (Silba adipata McAlpine) : empty pupa found in the soil.

Black Fig Fly: empty pupa found in the soil.

 

IDENTIFYING THE BLACK FIG FLY PUPA

 

Having simultaneously bred medflies (Ceratitis capitata Wiedemann) and black fig flies (Silba adipata McAlpine), I have been able to compare the pupae of the two species.

With practice, we easily recognize each other: the pupa of Silba adipata McAlpine clearly appears smaller and less rounded than that of Ceratitis capitata Wiedemann. The latter is slightly longer, much wider, and it generally has a greater width to length ratio.

Below, two photographs showing the differences between Ceratitis capitata Wiedemann pupae (on the left) and Silba adipata McAlpine ones (on the right).
 

Black-Fig-Fly pupae (on the right) and Medfly pupae (on the left).

Comparing Medfly (on the left) and Black Fig Fly (on the right) pupae.

 

Black-Fig-Fly pupae (on the right) and Medfly pupae (on the left).

Comparing Medfly (on the left) and Black Fig Fly (on the right) pupae.

 

HOW DEEP ARE THE BLACK FIG FLY PUPAE IN THE SOIL ?

 

For those who would imagine Black Fig Fly control methods destroying the pupae, or killing the nymphs inside the pupae, it is useful to know how deep are the pupae in the soil. I have observed the difficultty for the larvae to bury themselves in the soil depending on its texture, but I have no personnal observations about the burying depth.

Two authors give a response.

Filippo SILVESTRI, in its masterful study of the Black Fig Fly (morphology, biology, fig infestation...), published in 1917, indicates that the larvae burrow to a depth of 2 to 10 cm, before starting their pupation. 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.

Nihat SCHEWKET, who studied the Black Fig Fly in eastern Anatolia (Turkey), in the early 1930s, specifies for his part that the larvae burrow to a depth of 3 to 4 cm, before starting their pupation. Reference: SCHEWKET N., 1934, Die Feigeninsekten und die wesentlichsten Ursachen der FeigenfruchtfaŘle, Anzeiger fŘr Schńdlingskunde, Vol. 10, Issue 10, pp. 118-119 (article for sale).

Below, a photograph showing a young imago having emerged from the pupa and reached the surface of the soil. Note that the wings are not yet fully swollen to their maximal length, whereas the upper thorax is already black-colored - we can deduce that the imago came out the pupa at least one quarter of an hour ago.
 

Black Fig Fly (Silba adipata McAlpine) : young imago emerged from the soil.

Silba adipata McAlpine : young imago having emerged from the pupa and reached the surface of the soil.

 

 

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