Februaby 1, 1892.] 



KNOWLEDGE 



27 



formed wholly of Carbon atoms. All Carbon atoms are, 

 we believe, alike ; but this by no means necessitates the 

 identity of substances composed wholly of those atoms. 

 We must look upon diamond and charcoal as structures 

 both formed of the same material (the Carbon atom), but 

 built up in different ways. 



Regarded in this way the subject of ullutrdjii/ is easy to 

 understand, as easy as it is to understand, for instance, 

 that a certain .Jacobean house in Staffordshire is not a 

 Norman castle though buUt of the sandstone blocks which 

 once formed the feudal fortress originally standing on the 

 same site. Sandstone is the matter of which both the 

 house and the castle have been built, and in the same way 

 diamond, charcoal, and graphite are constructed wholly of 

 Carbon atoms ; but to say simply and without qualifica- 

 tion that diamond is Carbon, and that each of the other 

 two substances is Carbon, is to employ language somewhat 

 loosely and in a way which imdoubtedly leads to confusion. 



WHAT IS AN ANT? 



By E. A. Butler. 



OF late years the Ant, as everyone knows, has become 

 the pet of the scientific world, and, to some extent, 

 of the unscientific also. The fierce light of pub- 

 licity has been brought to bear upon these little 

 creatures, and upon their secret and subterranean 

 doings. The laws which govern their communities, their 

 common labours, their wars and foraging expeditions, their 

 individual intelhgence as manifested in their power of dis- 

 tinguishing their friends and detecting aliens, their vision 

 and perception of colour, their senses of smell and 

 hearing, their devotion to their young, their development 

 and the duration of their life — these, and other such items, 

 have been made the subject of observation and experiment, 

 and the results have been eagerly read and discussed even 

 in the daily press. But notwithstanding that Ants have 

 become so famous, and their doings have been so minutely 

 chronicled, there does not seem to be in the minds ot the 

 public generally a very distinct idea as to the identity of 

 the creatures themselves, or, in other woids, as to what 

 insects are Ants and what are not. When an entomologist 

 shows his collections to non-entomological friends, if he 

 happens to have amongst his specimens any little dark- 

 coloured, long-legged, wingless creatures, he is pretty sure 

 to hear the suggestion hazarded in an mquiring tone that 

 these must be Ants. Such a supposition wll, it is likely, 

 be quite as often wrong as right. The popular conception 

 of an Ant is no doubt derived from the little black or dark- 

 brown wingless individuals which one meets with every- 

 where, in our gardens and around our houses, quite as 

 much as in the fields, lanes, or woods. But a conception 

 which is formed merely by a random glance at such 

 minute objects in rapid motion, and seen without the help 

 of a magnifying glass, cannot but be vague in the extreme, 

 and it is not surprising, therefore, that mistakes should 

 frequently be made. The scientific idea of an Ant must 

 be a good deal broader as well as a good deal more definite 

 than this popular conception, and it is our purpose in this 

 paper to show what are the distinctive characteristics of 

 Ants, and how they can be distinguished from the 

 numerous other insects to which they bear a superficial 

 resemblance. 



One cannot pronounce off-hand of any little dark- 

 coloured, wingless, running insect, that it is an Ant, and, 

 on the other hand, many true Ants would be neither dark- 

 coloured nor wingless. Certain definite structural charac- 

 teristics, which are accomjjanied with certain well-marked 



peculiarities of economy and habits, serve to distinguish 

 Ants from other insects. Though what we have to say in 

 this paper is intended only to apply to British Ants, it will 

 be as well at the outset to correct a possible misapprehen- 

 sion, and to observe that there is a well-known tribe of 

 insects which inhabit tropical regions, and no members of 

 which are natives of Britain at all, that have unfortunately 

 been called Ants though they are of an entirely difl'erent 

 nature, whereby has resulted great confusion of popular 

 zoological ideas. The insects in question are the so-called 

 " White Ants," better named Termites, whose ravages are 

 one of the greatest trials and annoyances of tropical 

 countries. These destructive insects we have, quite apart 

 from geographical hmitations, nothing to do with here ; 

 zoologically they are not Ants at all : their structure is 

 very different from that of the true Ants, and in many 

 important respects their economy and habits are also strik- 

 ingly dissimilar. The reader will therefore be good enough 

 to exclude those creatures from his thoughts, and bear in 

 mind that nothing that is said has any reference to them. 

 The insects whose characteristics we have to consider are 

 those which in this country are known as Ants or Emmets. 

 We have between twenty and thirty kinds of them in this 

 country, and these differ greatly in colour, ranging from 

 the palest yellow, through various shades of red and brown, 

 to deep jet black. Nevertheless there is a family likeness 

 about them that renders them easily recognizable when 

 once the distinctive points are known. 



The first of these is to be found in the form of the insect. 

 There is a large head (see Fig. 1), which is more or less 

 abruptly cut off' square behind, where it is often at 

 its broadest. The head 

 contains within it the brain 

 and the muscles that 

 move the jaws, in addition 

 to the commencement of 

 the digestive tract ; and 

 when we remember, in 

 conjunction with this, the 

 high degree of intelligence 

 Ants manifest, and the 

 muscular strength that is 

 required for the hard work 

 the jaws have to do, in 

 fighting, in excavating, and 

 in carrying heavy weights 

 and unwieldy masses, often 

 larger than the insect it- 

 self, we shall see very good 

 reasons for the great size 

 of the head, and shall 

 naturally expect to find 

 it, as is reall}' the case, 



Fig. 1.- 



Ant 



Worker of Wood 

 (Formica riifa), 



largest in those members of 

 the community which have to do most of the work, 

 whether mental or physical, viz. in the workers. The 

 head is succeeded by a hump-backed thorax, often the 

 narrowest part of the body, and showing very distinctly its 

 composition out of three distinct segments. Then follows 

 the abdomen , which is often extremely small in proportion 

 to the other parts. Now it is in the construction of this 

 part of the body that one of the most characteristic Ant- 

 features is to be found. The front part of the abdomen is 

 drawn out into a kind of thin stalk, which forms the con- 

 necting link between it and the thorax. But as this is the 

 case with the majority of the Hymenoptera, to which order 

 the Ant belongs, and gives them the narrow-waisted appear- 

 ance which is familiar in wasps and ichneumon flies, it is 

 not in the mere presence of this petiole, as it is called, that 

 we find the distinguishing feature, but rather in its peculiar 



