Hi 



KNOWLEDGE. 



[]\Iav 1, 1895. 



position necessitated by the reduction of the number of 

 their claspers from five pairs to two. Turning to another 

 section, the hairy and thick-bodied moths called Bombyces, 

 •we find two species, externally very like their congeners, 

 but diti'ering in emerging during the winter months. 

 These are called the small egger (Enni/iister lanestris), and 

 the December moth {Pircilncnmpa pojnili). The former 

 appears in February, and the latter in November and 

 December, the normal time being these months in the 

 winter following the summer of their larval existence. 

 But the date of their exit from the cocoon is extremely 

 uncertain, and their appearance is often delayed for two or 

 three years. It is a well-known fact that an increased 

 temperature may result in the more speedy development 

 of a lepidopterous insect when it is in the pupa state, and 

 advantage is taken of this fact by collectors who " force " 

 species to emerge at unusual times. Hence one might 

 readily conclude that a lowering of temperature would 

 have a retarding effect, and that, therefore, such retardations 

 as just mentioned might take place in consequence of an 

 exceptionally severe winter. But that conditions of 

 weather are not wholly responsible for such freaks is 

 evidenced in two ways : first, that the warmth of summer, 

 which, however unfavourable the weather may be, will be 

 certainly higher than that of exceptionally severe winters, 

 does not cause an emergence, but if the insect does not 

 come out during the first winter, it waits till the next 

 comes round ; and second, that different members of the 

 same batch, which all pupated at the same time, and have 

 all been exposed to the same conditions of temperature, 

 emerge at very different times, some during the first 

 winter, others during the next, and so on. 



Amongst the Noctuae, or ordinary thick-bodied moths, 

 there are many species, notably those of the genus Tienio- 

 rawjiii, that complete their pupal development just at the 

 end of winter, and so appear as perfect insects at the com- 

 mencement of spring, when they become noted visitors at 

 the catkins of the sallows, which are just then in season. 

 These, though hardly to be classed as winter moths, serve 

 as the connecting link between the truly winter species 

 and the long series of forms that emerge in unbroken 

 succession during the latter part of spring and the whole 

 of summer; and, further, they serve to emphasize the 

 variety that exists in this order in the time of occurrence 

 of the chief changes in the life of the insect. Amongst the 

 smaller moths there is a pretty little greyish species called 

 Diurnra /(ujdla, which must also be ranked amongst those 

 that assume the perfect form in winter. It is a narrow- 

 winged insect, which, when resting on tree-trunks looks 

 much like a little scrap of lichen, and it is one of the 

 earliest heralds of the new year, enlivening the yet leafless 

 woods with its short and rather weak flights. 



But a warm day in winter may be enlivened by the 

 appearance of other lepidopterous insects than those that 

 actually acquire the winged form at that season, and never 

 live to see the brightness of summer suns. Several species 



hybernate as perfect insects, and 



a particularly warm day may 



^^^^^ /^^^^L entice these from their retreats. 



^^^^K^^L^^^^^g Amongst our buttcrtlies there 



^^^^^K^^^^^^ ^I'e two species that must speci- 



^^^^^^^^^^^ ally be mentioned in this con- 



l^^^VV^^^^P nection, the small tortoiseshell 



l^^f ^i^V ( r^ojcs.srt Hrt/tw) (Fig. 2) and the 



Fig. 2.-Snmll Tortoisoshcll brimstone [Gonrpteryx rkamni). 



'B\xt\.er&y (^Tanesmnrfica). The former, one of the most 



richly coloured of our British 



butterflies, belongs to a section which is remarkable for 



the dissimilarity in colouring that exists between the upper 



and under sides of the wings. The reddish ground colour 

 of the upper surface passes through various shades from 

 almost scarlet, through deep orange to yellowish. This 

 reddish-orange background is strikingly relieved by angular 

 patches and spots of the deepest black, one of which is 

 bordered by a white patch at the tip of the fore-wing. A 

 brr ad black band at the hind margin is inlaid with a series 

 of exquisite blue crescents, and then beyond these there is 

 a chaste border of delicately mottled brown running out 

 into a blunt point or tail on each wing. Now, if we turn 

 the creature over on its back, we discover that the under 

 surface exhibits the same general pattern, but in much 

 duller tints, dirty blackish-brown and pale ochreous 

 being the prevailing ones. Like its brethren, this butterfly 

 rests with its wings closed over its back, and thus the 

 glowing brilliance of the upper surface is entirely hidden, 

 and nothing but the dulness of the under surface appears, 

 and this is so inconspicuous that it is quite possible to 

 look at the spot where the insect is resting, perched on 

 some twig, without becoming aware of its presence. 

 Hence the dulness of the under surface must be a valuable 

 means of protection to it, often enabling it, no doubt, to 

 escape the passing notice of hungry birds. Thus there is 

 no difficulty in understanding how, from the similarity of 

 their under colouration to that of dead leaves and dry 

 twigs or tree trunks, they can remain completely concealed 

 throughout the winter, and come out again in spring-time, 

 to complete their cycle of 



existence. It follows, there- ■•.•„, ^,^ 



fore, that all the tortoiseshell '■; ^'--. , ' ^ 



butterflies one sees in spring 

 or early summer are the same 

 individuals that were to be 

 met with during the autumn 

 of the preceding year, and 

 their antiquity is evidenced by 

 the dingy and worn condition yio 

 of their wings, so different 

 from the brilliance and perfect 

 symmetry of a newly-fledged 

 hybernate in houses or public 



3. — Brimstone Butterflv 

 {fiouepferifx rham)ii). 



individual, 

 buildings, 



They often 

 and a sudden 

 accession of artificial warmth indoors, equally with 

 a natural rise of temperature out of doors, may at any 

 time call them out into premature activity. 



With the brimstone butterfly the case is somewhat 

 different. This insect (Fig. 3) is almost entirely of a 

 bright sulphur colour above, and the under surface is 

 almost the same, the only difference being that it is a little 

 paler. It rests with wings closed as usual, but this, of 

 course, does not make much difference to its colour. The 

 pale greenish -yellow of the under side serves admirably to 

 conceal the insect amongst the (irecn foliage of summer- 

 time, but it seems at first sight difficult to understand how 

 it can be otherwise than most conspicuous in winter, when 

 there is such an absence of light-green leaves. But, 

 accordmg to Bossier and De Selys-Longchamps, they 

 hybernate amongst fallen leaves ; and as, in sheltei'ed 

 places, these often retain their colour 

 for some time, the colour difficulty is, 

 perhaps, less than might have been 

 imagined. They have also been found 

 in cracks in the ground, sometimes at 

 a considerable depth. Both sexes of 

 these two butterflies live through the 

 winter. The eggs are laid in April and 

 May, and, according to Dr. Chap- 

 man, fertilization takes place, at 

 only shortly before their deposition. 



Fig. 4.— Herald 

 Motli ( Qoiwpiera 

 h'hafri.i'\ 



least 

 Thus 



sometimes, 



we see that these two butterflies — and the case 



