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 z\ 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 larvae 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. cogmta, 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 {Chrysopidce), sometimes called 'golden-eyes,' are really common 

 insects, though not frequently noticed. They are however of consider- 

 able importance since their larvae, which feed most voraciously on 

 aphides, are to a great extent instrumental in keeping these pests in 

 check. The aphidivorous habits of the larvs of the alHed family 

 Hemerobiidce are equally noteworthy ; and the larvae 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 {Pamrpa), 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 

 {Trichoptera) 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 larvae 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. 



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