Black-legged Alderfly
Sialis nigripes Pictet, 1865
Order Megalopterous flies (Megaloptera)
Family Alderflies (Sialidae)
Conservation status: in Bulgaria: Critically Endangered CR [B1ab(iii)+2a].
General distribution. Ireland, Great Britain, Belgium, the Netherlands, Germany, Denmark, Poland, Spain, France, Italy, Switzerland, Austria, the Czech Republic, Slovakia, Hungary, Slovenia, Croatia, Bulgaria and Greece.
Distribution and abundance in Bulgaria. Known only from Sinovishte Lake near Devetaki Village, Lovech Region (1967) [1]. The restricted area of the only locality serves as evidence of a probably rather small population.
Habitats. In Bulgaria, karstic lakes, inhabited by the water larvae, and vegetation around them, inhabited by the adults. Sinovishte is a non-flowing lake with a length of 130 m and a depth of 5 m. In Central Europe the species prefers flowing lakes with a larger area [2].
Biology. The adults are diurnal, they almost do not eat and are found in April (in the rest of the range from the middle of May to the end of June). They lay about 900 eggs on dry grasses and thin small branches at a distance between 0.5 and 3 m over the water surface but not on the green shore vegetation [2]. The hatched larvae fall into the water. The young larvae swim freely, and the mature ones live in the silt of the bottom of standing water bodies, being active during the night. They feed on worms, molluscs and insect larvae. The number of larval instars is about 10. The last instar larvae go out onto the shore where they pupate. The development cycle lasts for two years with two overwinterings of the larvae.
Similar species. Sialis lutaria and S. fuliginosa. It differs from them in the structure of male and female genitalia.
Negative factors. Marshing of the karstic lake. Water pollution by animal breeding. Restricted distribution and low density. The water larvae of Sialis nigripes are strongly vulnerable during pollution of the small water body, the only one they are found in in Bulgaria.
Conservation measures taken. None.
Conservation measures needed. Restoration of the habitat by bringing back the natural appearance of the lake that is gradually becoming marshy. Study of the abundance and the area of the population and of the status of the habitat. Monitoring.
References. 1. Popov, 1981; 2. Holzel, 2002.
Author: Alexi Popov
