Post by Melly on Feb 26, 2005 21:28:36 GMT
Speyeria adiaste atossa
The Unsilvered, or Atossa, fritillary was last seen in 1960. This southernmost subspecies of Speyeria adiaste was known to be abundant in several southern California mountain ranges, particularly near Mt. Pinos in the Transverse ranges and in the Tehachapis further to the east. However, during the 1940's and 50's, collectors noticed a decline in its numbers. The last sighting in 1960 was near the peak of Mt. Pinos. Hope persisted that in more remote parts of the butterfly's range some small populations might still exist, and it is still a possibility. However, several surveys have not turned up any sightings.
The reasons for the Atossa fritillary's decline are rather unclear. Several other species of Speyeria occur in different portions of its former range. A severe late drought in the late 1950's has been blamed for its final extirpation. However, the subspecies was clearly on the decline prior to this time. Whether its disappearance may be related to a host plant issue is also unknown. Because the larva of the Atossa fritillary was never discovered, it can only be assumed that it fed on Viola species like other members of the genus. For this subspecies to have disappeared from areas that are largely undisturbed indicates that the cause may not be external. A disease may be a possibility.
For further reading:
Orsak, L. J., 1975. Project Atossa -- Preliminary report. Atala 2(2): 5-8.
The Unsilvered, or Atossa, fritillary was last seen in 1960. This southernmost subspecies of Speyeria adiaste was known to be abundant in several southern California mountain ranges, particularly near Mt. Pinos in the Transverse ranges and in the Tehachapis further to the east. However, during the 1940's and 50's, collectors noticed a decline in its numbers. The last sighting in 1960 was near the peak of Mt. Pinos. Hope persisted that in more remote parts of the butterfly's range some small populations might still exist, and it is still a possibility. However, several surveys have not turned up any sightings.
The reasons for the Atossa fritillary's decline are rather unclear. Several other species of Speyeria occur in different portions of its former range. A severe late drought in the late 1950's has been blamed for its final extirpation. However, the subspecies was clearly on the decline prior to this time. Whether its disappearance may be related to a host plant issue is also unknown. Because the larva of the Atossa fritillary was never discovered, it can only be assumed that it fed on Viola species like other members of the genus. For this subspecies to have disappeared from areas that are largely undisturbed indicates that the cause may not be external. A disease may be a possibility.
For further reading:
Orsak, L. J., 1975. Project Atossa -- Preliminary report. Atala 2(2): 5-8.
