•i20 



KNOWLEDGE 



[October 1, 1890. 



FtG. 7. — ^Left Elytron of 



CaLOCORIS BirUNCTATUS. 



a, coriura ; h, clavus ; r, 

 cnneus ; d, membrane. 



nised, though in a greatly abhre\nated form, onp of the | 

 essential elements of the hemipterous wing, and it will be 

 necessary here to consider the general plan of the com- 

 plete wing, if we are to miderstand the ridiculously 

 reduced and utterly inefficacious scraps which the bed-bug 

 retains, perhaps as the relics of a former superabundance. 

 In hemipterous insects generally, then, the fore-wings, or 

 rather elytra, are so constructed that some of the prin- 

 cipal nervures divide them very distinctly into separate 

 areas, at the junctions of which the wing can be angu- 

 larly bent do-miwards ; the degree to which this is the 

 ease varies in different species, and we will take one of 

 the commonest insects we possess as illustrating a very 

 usual type, and one of considerable complexity. During 

 the summer months there may be found in profusion on 

 many wayside weeds, as well as 

 «■ u on plants in gardens, a bright 



green insect, a little over \ inch 

 long, wliich by an inspection of 

 its mouth, or by its odour, may 

 be easily recognised as a mem- 

 ber of the order Hemiptera. 

 Its name is ('ahiroris hipxnctatus, 

 and it is an active four-winged 

 creature, which readily talies 

 to flight ; a few specimens may easily be secured in a 

 pill-box, and thence transferred to a killing bottle. After 

 death, the fore-wings may be easily detached and mounted 

 on white cardboard, when they will be ready for examina- 

 tion with a lens. 



Fig. 7 shows one of the elytra of this msect ; the basal 

 part is rather stiff and horny, and brightly coloured with 

 green or orange : the tip is of much more delicate texture, 

 being quite thin, flexible, and transparent, and devoid of 

 bright colour. This difference of texture in the two parts 

 of the wing, which is a very constant 

 character, is the foundation for the 

 name Hemiptera, i.i'. " /la/y'-wings," 

 as well as for that of Heteroptera, 

 /'.(•. " disaimihir wings." The horny 

 basal part consists of two areas 

 dinded by a flexible jimction ; the 

 outer one, a four-sided piece, with 

 two long and two short sides, being 

 called the roriuni. and the inner, a 

 roughly triangular piece, the ihmis. 

 At the margm of the corium furthest 

 from the body is a small triangular 

 Elytra of Calocoris or wedge-shaped area, almost as stout 

 BiPUNCTATDs. as the corium itself, but distinctly 



;/', clavus; divided both from it and from the 

 more remote part ; it is called the 

 niiifiix. The rest of the wing, consti- 

 tuting the whole of the tip, is quite 

 flexible and is spoken of as the inmi- 

 hrane. When the elytra are closed 

 (Fig. 8), the shortest sides ol the two triangular cla^•i 

 exactly meet on the back below the apex of the scutellum, 

 while the inner edges abut on its sloping sides. The 

 membranes, however, overlap one another, and the elytra 

 then extend at least as fiir as the end of the body, not 

 unfrequently projecting a little beyond it. 



Such is one of the commonest types of fore-wing in the 

 Heiiiiptei'a ; but it is a peculiar fact that in this particular 

 order the dift'ereut areas of the wing seem possessed of 

 varying degrees of stability, so to speak, and nothing is 

 more common than for one or more of these parts either 

 to be very much reduced in size or to remain altogether 

 undeveloped, not as a mere accident in some one unfortu- 



«,c 

 r. cnnens ; rf, mem- 

 brane ; e, scutellum ; 

 ./", prolhorax. 

 The right membrane 



overlaps the left. 



nate individual, which may take place in any order, but as 

 a permanent arrangement for the whole species. The 

 membrane is the first part to be affected, and in many 

 species it either disappears entirely or is reduced to a mere 

 narrow border on the harder part of the wing. The 

 cimeus is in many cases omitted altogether, and in the so- 

 called apterous forms, of which the bed-bug is one, both 

 the clavus and corium may be reduced to an indefinite 

 extent. Now, in the bed-bug there is only one scale like 

 piece on each side without subdivisions ; this is a rudi- 

 mentary corium ; clavus, cuneus, membrane, are all 

 absent. The elytron, thus abbrcNiated, is a somewhat 

 oval, reddish brown object (Fig. 9), very deeply punctured, 

 i.e. covered with rounded pits, not perforations, wliich are 

 technically called punctures. Similar punctures cover the 

 whole body, except where the segments overlap, in which 

 places the surface is smooth and polished, whereby friction 

 is lessened ; the punctures on the elytra are, however, 

 larger than elsewhere, and each gives origin to a hair. 



The hind-wings of the Hemiptera are as unstable as the 

 fore-wings, and very generally, if the latter are abbreviated, 

 the former are entirely absent. When present, they con- 

 sist of an extremely delicate membranous expansion sup- 

 ported on a few nervures ; they may be seen in one of 

 their most beautifid forms in such insects as the Water 



Fig. ',1. — Left Elytron Fig. 10. — Umikhside of Thora.x of 



OF Bed-Bug. Bed-Bug. I, tip of rostrum; c, c„ c,,, 



eoxa> of 1st, 2nd, and 3rd pairs of legs ; 



l^ //, //// 1st, 2nd, and 3rd pairs of legs ; 



s, flap under which the scent of glands lie. 



Boatman {Notnnirtn i/lmivn), or in the water-bugs called 

 Coii-vce. The bed-bug has no hind-wings at all. 



But there is a further puzzling peculiarity connected 

 with the wings of the Hemiptera that is worthy of thought- 

 ful consideration. Those species in which the wings are 

 usually more or less imperfectly developed, occasionally 

 yield individual specimens in which the full degree of 

 development is attained, all the parts being present in their 

 proper proportions. Such cases are usually rare, some- 

 times extremely so, and the causes which produce the fully 

 matured forms still await discovery. Take, for example, a 

 very common insect, the so-called Ditch Skater, or Water 

 Cricket {Vclui rurrrns). Everyone will remember to have 

 seen this creature living gregariously on the surface of 

 ponds or streams, skating about in lively fashion, like a 

 company of spiders enjoying an aquatic picnic. Almost 

 always this insect is entirely destitute of wings, showing 

 not even the merest rudiments of them. And yet, very 

 occasionally, amongst a crowd of specimens, all of the 

 ordinary form, there may be detected an individual with 

 fully formed elytra and wings, and therefore capable of 

 flight. But the occurrence is a most exceptional one, and 

 the discovery of a /»//// tliirlopiil VAiii always marks a red- 

 letter day in the diary of an hemipterist. And tlie same 

 thing holds good of the majority of those bugs which as a 

 rule have undeveloped wings. 



Now, as our domestic pest is one amongst the number 

 of these imfinished forms, the question arises whether it 

 ever assumes the fully winged condition, and if so, what 



