Sinai baton blue (Pseudophilotes sinaicus)

GenusPseudophilotes (1)
SizeWingspan: c. 9.5 mm (2)
Smallest wingspan: 6.25 mm (2)
Caterpillar length: up to 9 mm (2)
Top facts

The Sinai baton blue is classified as Critically Endangered (CR) on the IUCN Red List (1).

A diminutive butterfly found only in a tiny part of Sinai, Egypt, the Sinai baton blue (Pseudophilotes sinaicus) may potentially be the world’s smallest butterfly species. The upperside of the male’s wing is a brilliant blue, while that of the female is dark brown. Both the male and female Sinai baton blue have a distinct black bar on the wing, and black fringing with a white border (3).

The underside of the wing of the Sinai baton blue is identical in both the male and female, with black spots on both wings and orange spots on the hind wing (3).

The Sinai baton blue caterpillar is usually bright green with a double row of yellow-green markings and a small black head, and its body is covered in short white hairs. The pupa is a uniform light brown, and measures around six millimetres in length (2).

The Sinai baton blue is endemic to the St Katherine Protectorate, southern Sinai, Egypt, where it occurs only at elevations above 1,800 metres. The entire world distribution of this species occupies a mere seven square kilometres (1).

The distribution of the Sinai baton blue is dependent on its host plant, as the larvae feed exclusively on the buds and flowers of Sinai thyme (Thymus decussatus). This plant has a patchy distribution, growing best in well-defined soils, restricting the Sinai baton blue to 25 thyme patches (4).

Within these areas, the Sinai baton blue prefers sheltered patches with relatively large thyme plants (4).

The main flight period of the Sinai baton blue, when the adults are active, is from May to mid-June. Due to its small size, the adult butterfly is relatively sedentary, rarely flying more than 50 metres (4). The adults of this species feed almost exclusively on the nectar of Sinai thyme (T. decussatus), but will also occasionally feed on nectar from other plants (2).

The female Sinai baton blue lays around 26 eggs on average, depositing each one individually on a Sinai thyme inflorescence. The tiny white eggs measure approximately 0.5 millimetres in diameter and hatch after a few days. The larval development stage is presumed to take approximately 21 days, during which time the larva goes through a series of moults. The larvae of the Sinai baton blue are relatively immobile, remaining on the plant on which the eggs were laid and feeding on its buds and flowers, before pupating in the soil below. The pupae remain in the soil over winter, hatching into adults in the following year (2) (5).

The caterpillars of the Sinai baton blue sometimes associate with ants, which protect and tend to them. In return, the caterpillars secrete sugary droplets that the ants consume (2).

The Sinai baton blue and its host plant have been marooned on the Sinai mountaintops by climate change over the last 5,000 years, as they inhabit a very harsh, arid, mountainous environment which in many years has little or no rainfall (6). Further changes to the climate caused by human activities may result in even greater reductions in the available habitat for this species (1).

Other threats to the Sinai baton blue include human disturbance and collection of the host plant for medicinal purposes, which are likely to reduce available resources and push both the butterfly and its host plant towards extinction (6).

The Sinai baton blue occurs entirely within the St Katherine Protectorate, where rangers are monitoring this species by carrying out 9 to 14 survey days each year (7). Recent conservation efforts for the Sinai baton blue are mainly focused on preserving its endangered host plant, with the Protectorate recently banning the collection of Sinai thyme with enforced fines. A fence has also been erected around a patch containing the largest butterfly population, to prevent public access and stop further plant loss. Two dams have been built in this patch to hold more water in the soil and improve the condition of the thyme (1) (8).

The rangers in the St Katherine Protectorate have also tried to increase public awareness for this tiny butterfly, which is considered to be a flagship species for the area (8).

Find out more about conservation efforts for the Sinai baton blue:

Information supplied and authenticated (03/07/2012) by Katy Thompson, PhD student, University of Nottingham.

  1. IUCN Red List (June, 2012)
  2. James, M. (2006) The natural history of the Sinai baton blue: the smallest butterfly in the world. Egyptian Journal of Biology, 8: 67-83.
  3. Nakamura, I. (1975) Descriptions of two new species of butterflies (Lepidoptera, Lycaenidae) from the South Sinai. Journal of Entomology, 44(3): 283-295.
  4. James, M., Gilbert, F. and Zalat, S. (2003) Thyme and isolation for the Sinai baton blue butterfly (Pseudophilotes sinaicus). Oecologia, 134: 445-453.
  5. James, M. (2006) Immigration and emigration in the Sinai baton blue butterfly: estimates from a single patch. Egyptian Journal of Biology, 8: 39-50.
  6. Hoyle, M. and James, M. (2005) Global warming, human population pressure, and viability of the world's smallest butterfly. Conservation Biology, 19: 1113-1124.
  7. Gilbert, F., Rashad, S., Kamel, M., El-Din Ismail, A., James, M. and Zalat, S. (2010) Monitoring of the endemic Sinai baton blue butterfly Pseudophilotes sinaicus in the St Katherine Protectorate, South Sinai. Egyptian Journal of Biology, 12: 18-26.
  8. El-Deen Ismail, A. (2010) Sinai Baton Blue Conservation Project: Final Report. Rufford Small Grants Foundation, UK.