A peculiar finding was discovered in the Sakhalin Regional Museum by employees in the first decade of January 2019. A butterfly pupa (Photo 1) attached to the wall of the Administrative Building of the Museum was identified by museum experts. It turned out to be a chrysalis of Papilio bianor, (Achillides bianor). Papilio bianor is a rare species of butterfly in the family Papilionidae. People call it the «Blue Swallowtail» (Photo 2).
Photo 1. Pupa (green colour), January 2019
Papilio bianor is listed in the Red Book of the Sakhalin Region (2016). The species is protected on the territory of the Kurils Nature Reserve. The butterflies Papilio bianor belong to insects living in deciduous and mixed forests and do not rise on the slopes of river valleys above 450 m above sea level. The range of butterfly covers Sakhalin Island, Moneron Island, the South Kuril Islands (Kunashir Island, Iturup Island), Popov Island (Primorsky Krai), as well as the islands of Japan, the peninsula Korea, China. A serious threat to the population of these butterflies comes from deforestation, in which its forage plant grows Sakhalin velvet (Phellodendron sachalinensis). Sakhalin velvet grows in the south of Sakhalin, Moneron and the South Kuril Islands.
Photo 2. Papilio bianor butterfly (Achillides bianor)
Earlier, entomologists expressed assumptions that Papilio bianor spend winter as a pupa (Vertyankin, 2016; Klitin, Vertyankin, 2011). This finding confirms that the species actually hibernate in the pupal stage.
In 2018, in the third decade of July, lots of species of Papilio bianor were observed flying in the museum garden. We assume that the reason for the large number of butterflies flying in the garden were favorable weather conditions: the average air temperature was +17.2°C, the relative humidity was 83%. In June, however, the weather was cooler +10,9°C, the relative humidity was 79 %. As the Sakhalin entomologist A. K. Klitin noted, butterflies emerge mainly in the period from mid-June until the second decade of August (Klitin, Vertyankin, 2011), according to other sources from mid-June to late August (Vertyankin, 2016). It is noteworthy that in the first days of the second decade of August, only single butterflies were observed in the museum garden. Probably, the second decade of July the first decade of August was the beginning of the egg-laying period of Papilio bianor. According to the entomologist Yu. P. Korshunov, females lay eggs one by one on the lower side of the leaves of the Sakhalin velvet (Korshunov, 2002), which also grows on the territory of the museum garden.
In the first days of September, swallowtail caterpillars (Papilio bianor) were found descending down the tree trunk of Sakhalin velvet in the garden of the museum (Photo 3). Once on the ground, they went (crawled) on the ground and on asphalt in the direction of the nearest buildings and to the Museum Administrative Building. In order to save the caterpillars, they were taken back and placed on trees, but they again descended to the ground and returned to the museum building again.
Photo 3. Older Papilio bionar caterpillars on Sakhalin velvet
At the beginning of the second decade of September, caterpillars were found attached to the walls of the Administrative Building and outbuildings in places which had been well warmed by the sun. Some of them had already gone into the pupal stage at that time. The caterpillars were low to the ground, putting a silk thread in front of their head (Photo 4).
Photo 4. Caterpillar attached to the wall of the Museum Administrative Building
At first, the pupae had a light green color which in four (4) days changed to a darker one with a light pink stripe on the sides. The pupae were belted with a thread at the base of the wings, which departed from the place of its laying on by a caterpillar (Photo 5).
Photo 5. Pupae
Sufficiently solid components of the pupa cover protect its contents in the winter time from external influences. In addition, wintering is preceded by a certain physiological preparation of the organism when free glycerol accumulates in the insect tissues, which prevents the insect from freezing. Unfortunately, most butterfly pupae still die from external environmental influences. In addition, the museum staff watched the sparrows pecking the pupae.
Papilio bianor pupae will be monitored until the butterflies emerge.
Prepared by: V.A. Dubinina, O. E. Lebedeva, G. V. Matyushkov.
Photos: V.A. Dubinina
A.V. Vertyankin Insects // The Red Book of the Sakhalin Region: Animals. M .: Buki Vedi, 2016. P. 181199.
A.K. Klitin , A.V. Vertyankin A. V. The Order of Lepidoptera, or Butterflies Lepidoptera / The Natural History of Sakhalin and the Kurile Islands. Insects. Yuzhno-Sakhalinsk, 2011. p. 116119.
Yu.P.Korshunov, Butterfly (Lepidoptera) of Northern Asia. M.: Partnership of Scientific Publications KMK. 2002. P. 419
The Red Book of the Sakhalin Region: Animals. M .: Buki Vedi, 2016. P. 252