198 



KNOWLEDGE 



[September 1, 1894. 



Fig. 15. — Elood_v-nose 

 Beetle {Tiw arcka 

 teneb-ricosa.') 



properties, and are said to have been used as a specific 

 against toothache. 



Closely allied to the golden apple beetles, and indeed 

 belonging to the same family, is the well-known " bloody- 

 nose beetle " {Timarcha tenthrkosa) (Fig. 15), which is a very 

 common insect on wayside banks in 

 limestone districts. It is a large and 

 heavy, slow moving, very convex, 

 black creature, faintly tinged with 

 blue, with broad feet, which are of 

 great service to it as it slowly crawls 

 over the herbage. Its popular name 

 arises from its disagreeable habit of 

 exuding from its mouth and from the 

 joints of its limbs a clear red liquid, 

 which reminds one somewhat of the 

 colour of the blood of a vertebrate. 

 Here, again, one can only imagine a 

 protective function in this liquid. The 

 appearance is the most objectionable 

 feature of this secretion, there being 

 no very strong smell attached to it. But such is not the 

 case with the predaceous ground beetles, or Carahuta, all 

 of which pour out a fa?tid black or brown liquid from the 

 mouth when handled. A similar habit is exhibited by 

 many carrion feeders, and in this case, as might be expected 

 from the nature of the food, the liquid is still more foul. 



The evU odour of scavenger beetles, however, does not 

 always proceed fi'om the mouth. Among the rove beetles 

 there are many species that have a most repulsive odour, 

 and in their cases the glands are often situated at the 

 tail. The largest species of the group, Ocypus olem, the 

 " Devil's coach-horse," may be taken as an example. It 

 is a long, dull black creature, shaped something like a 

 gigantic earwig, attaining a length of upwards of an inch. 

 It is extremely active and remarkably courageous and 

 aggressive. It may often be seen running about at the 

 foot of brick walls, or by the side of pathways, where it is 

 provided with subterranean cavities for retreat if necessary. 

 But it is always prepared to show fight to any object, 

 however large, and if interfered with, at once faces the 

 intruder, and cocking up its tail, and raising its head, 

 glares open-jawed defiance at its opponent with an aspect 

 of the utmost ferocity. At the same time two milk-white 

 vesicles make their appearance at the tail, standing out in 

 bold relief on the dead black background of the body. A 

 very disagreeable odour proceeding from these vesicles is 

 soon perceptible, and makes one still less inclined than 

 before to press one's attentions on so formidable a being. 



The larger water beetles, again, emit an extremely fcetid 

 fluid when handled, but of the whole tribe, none perhaps 

 is 30 repulsive as the little shining whirligig beetles 

 (Gyrinidce), whose mazy gyrations on the surface of still 

 water must be familiar to everyone. These little, highly 

 polished creatm-es have the power of exuding an oUy milk- 

 white liquid from various parts of their bodies, which, 

 spreading over their shiny black surface, gives them the 

 appearance of having been dipped in milk. So acrid is 

 this liquid that the beetles must be an extremely un- 

 desirable article of diet, and, as they spend their life at the 

 junction of two transparent media, air and water, each of 

 which is inhabited by predaceous and insectivorous beings, 

 their villainous secretion no doubt serves them in good 

 stead against both sub-aquatic and aerial foes, as well as 

 possibly improving their means of flotation. 



One of the most remarkable of the numerous secretions 

 formed by beetles is that of the bombardier {Brachinus 

 crepitans) (Fig. 16). This is a small beetle with red head, 

 thorax, and legs, and bluish-grey wing covers. Itself 



predaceous, it is nevertheless hunted by larger species 

 which desire to prey upon it, and as speed and agility are 

 unavailable against its larger and more active pursuers, 

 it has developed a sort of battery of stern-chase guns, by 

 the aid of which it can effect a Parthian retreat, and bring 

 about the discomfiture of its foes. When 

 attacked it elevates its tail, and discharges 

 therefi'om towards its assailant a small 

 quantity of a liquid which instantly vaporizes 

 with a slight explosion, and forms a bluish- 

 white cloud. The expulsion of the liquid 

 appears to require a certain amount offeree, 

 and so volatile is it, that if the insect be 

 killed by plunging it into boiling water, the 

 heat volatilizes the liquid while it is still 

 hardier Beetle within the abdomen, and causes the latter 

 {Brachinus to Swell out to a considerable size. This 

 crepitans), insect is to be found not imfrequently in 



Zmeters ^''° *^^ ^"^""^^ °^ England, under stones, by the 

 banks of streams, &c. Its secretion is a 

 which acts as an irritant when applied to 



Fio. 16. — Bom- 



strong acid, 

 the skin. 



{To he continued.) 



THE WANDERINGS OF A SUNSPOT. 



By E. Walter Maunder, Hon. Sec, R.A.S., Physical 

 Superintendent Royal Observatory, Greenwich. 



DR. A. BRESTER, in his interesting " Theory of 

 the Sun," first published in 1888, and to which 

 he has again recently invited attention, speaks of 

 the singular manner in which spots are apt to 

 move forward during the stage of growth. Quoting 

 from Prof. Young, he writes ; " Every time a spot undergoes 

 sudden changes it ordinarily advances on the solar surface 

 by making a sort of leap." I do not propose to discuss 

 Dr. Brester's theory — at any rate on the present occasion — 

 but it seems to me that the proper motion of a sunspot 

 deserves a little more particular description than the above 

 sentence supplies, and, if I interpret the phenomenon 

 rightly, it fails to afford Dr. Bresterthat confirmation of his 

 theory which he supposes. 



Forward motion in a spot is certainly the kind of move- 

 ment which most readily attracts attention. It is a very 

 ordinary phenomenon of a particularly interesting type of 

 group, viz., the " trains " and " streams," to use Miss 

 Brown's nomenclature. A "train" or "stream" is "a 

 group of spots following each other in succession, having 

 nearly the same latitude, but varying in area and form." 

 When these spots are of considerable size and are not 

 closely connected, the group is called a "train." When 

 the constituents of the group are smaller and less widely 

 separated, the group is termed a " stream." 



A train or stream frequently shows itself first as a pair 

 of small spots. The preceding spot of the pair will then 

 move forward at a much quicker pace than its companion, 

 and new spots will break out around those first seen, 

 and especially along the line connecting them. The first 

 and last spots grow rapidly, but usually present different 

 characteristics ; the leader being circular and sharply 

 defined, with dark central nucleus, whilst the spot in the 

 rear is much more irregular in outline, not so dark in tone, 

 and with a smaller and more broken nucleus. As the leader 

 spot is the more definite and regular, and as it pushes its 

 way quickly forward whilst the rear-guard either halts 

 entirely, or even moves slowly backwards, its motion 

 naturally attracts great attention. This period of forward 

 motion is also very commonly one of rapid growth, and as 

 both phenomena are very frequently observed, it has no 



