May 1, 1895.] 



KNOWLEDGE. 



115 



Fig. 5.— Egg Bracelet of Lackey Moth (S. 



neusiria) round a Hawthorn Twig; magnified 



two diameters. 



of several moths is parallel — conduct their operations 

 upon a diflferent plan from that followed by bees and 

 wasps, in which fertilization takes place during the autumn, 

 and only the females survive the winter, to lay their 

 eggs in the spring. Amongst moths, two of the best-known 

 instances of hybernation in the perfect state are those of 

 the humming-bird moth {Miirntiihss(( stellatarum) and the 

 herald moth [Gonoptem libatrix) (Fig. 4), both of which 

 may be met with in houses or barns, and the latter some- 

 times under tunnels and bridges, or in caves. 



Some Lepidoptera pass the winter in the egg state, 

 and one of the most remarkable is the lackey moth 

 {Bomhij.r rifu.stria). This insect, though a close ally of the 

 small egger, has a very different life-history. The female 

 lays her eggs while the leaves are still on the trees, but 

 does not attach them to the leaves as most moths would do, 

 but glues them firmly round a twig in the form of a 

 complete bracelet (Fig. 5). If attached to the leaves, they 



would run great 

 risk of being 

 ruined when the 

 leaves fall, but 

 by being firmly 

 cemented to the 

 twigs, they are 

 able to resist all 

 the storms and 

 rains of winter, 

 and produce their brood when the next crop of leaves is 

 ready for them. Many species hybernate as larvas, some 

 of them when quite young and small, and others when 

 nearly full-grown. Some construct a roof of silk for their 

 protection in company, while others retire into crevices, 

 or under leaves or stones, and there rest solitary. A 

 very large number of species rest through the winter in 

 that condition which is evidently specially related to the 

 occurrence in nature of an interval during which there 

 is an absence of vegetable food, viz., the chrysalis state, 

 the break in animal activity thus coinciding with that in 

 vegetable growth. 



So little is known of the life-history of the great host of 

 two-winged flies, or Diptera, that inhabit these islands, 

 that it is scarcely possible to do more than speculate as to 

 the way in which most of them pass the winter. Some 

 certainly hybernate as perfect insects, and an extra warm 

 day will call them forth from their hiding-places, but their 

 vivacity is far inferior to what it is in summer-time. This, 

 at least, applies to the heavier-bodied flies. But there are 

 some species of gnat-like flies whose special time of 

 appearance is mid-winter. Such is Trichicera hiemaUs, 

 the so-called winter-midge, the dancing swarms of which 

 may often be seen enjoying themselves in the air when the 

 temperature is sufficiently high. According to the Rev. 

 A. E. Eaton, a temperature of a few degrees above freezing 

 point drives them to their retreats under boards, etc., but 

 it need not rise to more than seven or eight degrees 

 Centigrade for them to congregate in swarms and perform 

 their aerial gyrations. 



Amongst the Ilemiptera it is certain that very many 

 hybernate in the perfect form, and hence those specimens 

 that are to be found in the early months of one season are 

 the same as those that first appeared as perfect insects in 

 the preceding autumn. Hence, during each year, two 

 perfectly distinct sets of individuals put in an appearance. 

 Even those that are aquatic, to some extent, adopt similar 

 habits. The water-skaters {(.im-it:) (Fig. (>) will even leave 

 the water and in some way, either by jerking themselves 

 along on their stilt-like legs, or by flight, escape to a 

 considerable distance from their native pond, and go 



7% 



into winter quarters amongst low herbage, moss, etc. 



The skaters that one sees in spring and early summer, 



therefore, are last year's insects, and 



their descendants of the next generation 



begin to appear while their parents are 



still alive, so that both generations may 



be met with simultaneously, and on the 



same pond. As so very little is known of 



the life-history of this order of insects, it is p^^ ^ _ ^j,f^^.^^ 



scarcely possible to say anything more si<ater {Oerris 



definite about them. How, when, and lacustris). 



where they lay their eggs — these are 



questions to which, in most cases, no definite answer can 



be given. 



It is a most unusual thing for such an insect as a dragon- 

 fly to pass the winter in the perfect condition. According 

 to Mr. McLachlau, only one species is known to hybernate, 

 and that is not a British one. It belongs to the thin- 

 bodied section, and is found in France. It remains con- 

 cealed amongst heather during the cold weather, coming 

 out and flying about whenever the sun is bright enough. 

 Of the Orthoptera, space will not permit us to say more 

 than that the common earwig may be found at any time 

 during the winter, in hiding, but always ready to start 

 into activity, and that a small kind of grasshopper was on 

 one occasion found hyberuating contrary to custom. 



Finally, we may note that to hyberuating insects, in 

 whatever condition they may be, the greatest enemy does 

 not seem to be cold. After a severe winter, insects are 

 often much more plentiful than after a mild one, and the 

 explanation seems to be that while they can stand a con- 

 siderable reduction of temperature without damage, the 

 milder weather, which is usually also damp, encourages 

 the growth of mould, one of the greatest enemies of 

 quiescent insects, and keeps insectivorous creatures more 

 active than they would otherwise be. 



Koticts of Boofes. 



Popular Astronomy. ByCamille Flammarion. Translated 

 from the French by .J. Ellard Gore, F.R.A.S., etc. Pp. 679. 

 (Chatto & Windus.) When a work has reached a sale of 

 more than one hundred thousand copies, it is late in the 

 day to discuss its merits. Flammarion's " Astronomie 

 populaire " attained that distinguished place among 

 scientific works some time ago, and its excellence obtained 

 for the author the Montyon prize of the Paris Academy, 

 as well as other honours. Few translations, however, 

 are very successful, not so much because of the translators' 

 imperfect renderings of the originals, but because the 

 eloquent expressions which make an attractive pabulum 

 for readers of one nationality do not appeal to a public 

 used to another and a foreign idiom. M. Flammarion's 

 power to write in very popular language is undoubted ; 

 he is gifted with a vivid imagination, which he uses with 

 due regard to facts. But when we come to read this 

 translation of his most successful work, we confess that 

 much of the writing which appears so sublime to French 

 readers approaches the ridiculous when dressed in our 

 sober English garb. It is too flowery, too florid 

 altogether, to be read with pleasure. However, the fault 

 does not lie with Mr. Gore, who has translated the work 

 into as readable English as the original idioms permitted. 

 Here and there he adds notes of his own, and in a few 

 cases these are, perhaps, a little too numerous. The 

 following interpolations, for instance, on page 79, makes 

 the text look very strange: — "We have already seen 



