NEUROPTERA PLANIPENNIA—SIALIDAE, ALDER-FLIES, SNAKE-FLIES—PANORPIDAE, SCORPION-FLIES—HEMEROBIIDAE, ANT-LIONS, LACEWINGS, ETC.
Fam. VIII. Sialidae—Alder-flies and Snake-flies.
Four wings of moderate size, meeting in repose over the back at an angle; the hinder of the two pairs slightly the smaller; the anal area small or nearly absent, not plicate. Nervures moderately numerous, transverse veinlets moderately numerous, forming irregularly disposed cells. The metamorphosis is great; there is a quiescent pupa. The larva has the mandibles formed for biting, armed with strong teeth.
The Sialidae, though but a small family of only some six or eight genera, comprise a considerable variety of forms and two sub-families—Sialides and Raphidiides. The former group has larvae with aquatic habits possessed of branchiae but no spiracles.
Fig. 286.—The alder-fly, Sialis lutaria. Britain. A, With wings expanded; B, in profile.
Sialis lutaria is one of the commoner British Insects frequenting the vegetation about the banks of tranquil streams; it is well known to anglers, being used by them for a bait. According to Ronalds it is called the alder or orl-fly, and in Wales the humpback.
Fig. 287.—Portion of a row of eggs of Sialis lutaria. (After Evans.)
