Page:VCH Norfolk 1.djvu/124

 A HISTORY OF NORFOLK and considerable dexterity in the use of the net. So far as the number of different kinds is concerned, these insects are scarcely so well re- presented in Norfolk as might reasonably be expected, several species which occur not uncommonly in the London district being as yet unre- corded for this county. On the other hand, Norfolk appears to be the only county where one particular species of Mschna is now to be found. This is Mschna isosceles. Mull., an insect about 2| inches long, having a bright sienna-brown body with a triangular yellow spot just behind the base of the hind-wings. Something like sixty years ago it appears to have been not uncommon at Yarmouth, but it has been entirely lost sight of for many years, the most recent recorded examples being one taken by my colleague Mr. Thouless in the Norwich district within the last few years and two taken near Norwich in 1 87 1 by Mr. Barrett. The snake-flies {Rhaphidiidce) are easily recognized by their comparatively broad flat head and the neck-like appearance of the parts succeeding it ; they are rare insects, and occur only in wooded districts, where their larvs are believed to feed on insects that harbour in old timber. The females have a long slender exserted ovipositor. We have in Norfolk three out of the four British species, and with regard to one of these {R. cognata, Rbr.) Mr. McLachlan writes that he had never previously seen a native example less than sixty or more years old. The specimen in question was taken by Mr. Thouless in Foxley Wood, on the 14th June, 1886. The lacewing- flies {Chrysopida), sometimes called 'golden-eyes,' are really common insects, though not frequently noticed. They are however of consider- able importance since their larvas, which feed most voraciously on aphides, are to a great extent instrumental in keeping these pests in check. The aphidivorous habits of the larvae of the allied family Hemerobiidce are equally noteworthy ; and the larvx of some at least of the species in that family have the habit of covering themselves with the empty skins of the aphides which they have sucked. The scorpion-flies {Panorpidce), so called from the resemblance of the hind part of the body in the male to the tail of a scorpion, are also remarkable for the shape of the head, which is drawn out into a broad deflexed beak. Besides the common and well known scorpion-flies {Panorpa), the family Panorpidce contains Boreus hiemalis, which is of local interest from the fact that the first recorded British example was taken by Dr. Leach very many years ago at Costessey. The Boreus is a curious little insect about one-fourth of an inch long, and looks like a minute wingless scorpion-fly ; it occurs occasionally in moss from October to March, but has not, apparently, been taken in Norfolk for more than seventy years. The caddis-flies (Trichopterd) are moth-like insects of small or moderate size, sober colours and retiring habits ; the surface of their upper wings is more or less closely covered with hairs. Their larvs are aquatic, and the curious cases which they make of pieces of grass stems, small fresh-water shells, and aquatic debris generally are probably more familiar to non-entomolo- gical observers than the perfect insects. 92