Family Sialidae - Alderflies

Orl-fly (1)

Two former species of Sialis were transferred to Protosialis (P. americana and P. glabella) by Liu et al. (2015)(2)(3)

see Sialis

24 spp. within 2 genera in our area;(4)(3) 75 extant spp. in 8 genera worldwide reported by Liu et al.(2) (84 extant plus 8 extinct spp. listed in LDL, of which 60 extant plus 4 extinct spp. are in Sialis)(5)

1. Protosialis (2 spp.)

2. Sialis (22 spp.)

Small to medium-sized, typically 10-25 mm

Medium-sized insects with soft bodies and large, delicate wings. Similar to fishflies, Corydalidae, usually smaller. These characters differentiate:

Wing venation:

  

Key to Genera

Our two genera are separated as follows:(3)

1. Sialis - larva: mandibles with 2 subapical teeth; adult: head primarily black with yellowish markings

2. Protosialis - larva: mandibles with 3 subapical teeth; adult: head primarily yellowish with black markings

most speciose in Holarctic; among minor genera, one is Neotropical + Madagascar (12 spp.), two are restricted to Australia (4 spp.), one Oriental (3 spp.), one East Asian (2 spp.), and one South African (1 sp.)(5)

Adult are most often encountered in association with riparian vegetation adjacent to open water; larvae prefer ponds and lakes but can also be found in large rivers or pools in smaller, faster, streams where there is abundant silt. Some species appear to be restricted to warm streams, and some species are tolerant of polluted water.(5)

Adults generally appear to be largely non-feeding and may depend primarily on reserves sequestered in the larval stages.(5)

Larvae are aquatic:

  

Adults found, briefly, on vegetation near the aquatic habitats; they are rather short-lived, rarely persisting over two weeks. Females deposit eggs in one or more masses, generally on the stems or leaves of plants overhanging water.(5)

Adults are relatively weak fliers and are rarely found far from water; most active on warm, sunny days, especially in the morning(5)