Certain genera of small European ants of the group Myrmicini display some most anomalous phenomena. This is especially the case in _Formicoxenus_, _Anergates_ and _Tomognathus_. The facts known have, however, been most of them only recently discovered, and some obscurity still exists as to many of even the more important points in these extraordinary life-histories. {160}[Illustration: Fig. 69.—_Anergates atratulus_. Europe. A, male, with part of hind leg broken off; B, female, with wings: C, female, after casting the wings and becoming a queen.] It has long been known that the little _Formicoxenus nitidulus_ lives as a guest in the nests of _Formica rufa_, the wood-ant; and another similar ant, _Stenamma westwoodi_, which shares the same life, was declared by Nylander and Smith to be its male; it was however shown some years ago by André that this is a mistake, and that _S. westwoodi_ is really the male of another ant that had till then been called _Asemorhoptrum lippulum_. This correction left the workers and females of _Formicoxenus nitidulus_ destitute of a male, but Adlerz has recently discovered that the male of this species is wingless and similar to the worker, the female being a winged Insect as usual. It is very curious that the characters by which the male is distinguished from the worker should vary in this species; but according to Adlerz this is the case, individuals intermediate in several points between the males and workers having been discovered. This phenomenon of quite wingless males in species where the female is winged is most exceptional, and is extremely rare in Insects; but it occurs, as we shall see, in one or two other Myrmicides. Charles Darwin made the very reasonable suggestion that winged males may be developed occasionally as an exceptional phenomenon, and it is very probable that this may be the case, though it has not yet been demonstrated. _Formicoxenus nitidulus_ occurs in England in the nests of _Formica rufa_ and of _F. congerens_, but we are not aware that the male has ever been found in this country. The genus _Anergates_ is allied to _Formicoxenus_, and occurs in Central Europe, but has not been found in Britain; the female, as in _Formicoxenus_, is winged and the male wingless, but there is no worker-caste; the male is a rather helpless creature, and incapable of leaving the nest. The species lives in company with _Tetramorium caespitum_ a little ant very like _Myrmica_, and not uncommon in South-East England. The female _Anergates_ is at {161}first an active little creature with wings, but after these are lost the body of the Insect becomes extremely distended as shown in Fig. 69, C; the creature is in this state entirely helpless, and as there are no workers, the _Anergates_ is completely dependent, for the existence of itself and its larvae, on the friendly offices of the _Tetramorium_ that lives with it. The mode of the association of these two Insects is at present both