The karyotypes of 94 species of Indian ants were examined. Their chromosome numbers range almost continuously between n=5 and 38, though the frequency distribution is bimodal with a remarkable antimode at n=11 and two modal points at n=10 and 15. Based on this bimodal distribution, Indian ants were classified into two groups: Lower-numbered species (n<_11) and higher-numbered species (n>11), the former being characterized by metacentric-rich karyotypes, and acrocentrics predominate in the latter.The three major subfamilies (Ponerinae, Myrmicinae, and Formicinae) showed a highly divergent distribution in chromosome number, ranging between n= 7-38, 6-35, and 8-27, respectively, suggesting a convergence in karyotype evolution of each subfamily, Another three subfamilies, of which only a few species were examined, had moderate or lower numbers, i.e., n=5-14 in Dolichoderinae, n=14 in Cerapachyinae, and n=12 in Dorylinae. We found four Robertsonian polymorphisms, two pericentric inversion polymorphisms, and four reciprocal translocations, three of which were fixed. Robertsonian polymorphisms were found only in higher-numbered species, while translocations were restricted to lower-numbered species. A possible biological significance for this nonrandom distribution of rearrangements is discussed with reference to karyotype evolution in ants.

A new species of Technomyrmex (T. caritatis sp. n.) is described based on workers and larvae from Dominican amber (Oligocene to Lower Miocene). These are preserved with eggs and pupae of the same species and with five other insects in one amber piece found in the Palo Quemado Mine, near Santiago and in two separate amber pieces collected in Carlos Diaz Mine. Both mines are in Cordillera Septentrional. Iridomyrmex hispaniolae Wilson is redescribed and transferred to Technomyrmex. Most Technomyrmex species occur from Africa, east through southern Asia, to Australia. One species transported by human activity is known in the New World and there is only one extant native Neotropical species recorded from Panama. Technomyrmex likely represents a case of an Old World ant genus undergoing extinction in the New World. We discuss the affinities of this genus with the extant Dolichoderinae and the phylogeny of the subfamily.

The traditional hypothesis that ant soldiers originate from large size workers is rejected in favour of their direct origin from gynes. This conclusion is supported by the first report of soldiers smaller than workers, by an intercaste morphometric comparative analysis by means of D'Arcy Thompson's transformation grids and by phylogenetic studies on Cephalotes showing that the cephalic shield appeared ancestrally among soldiers and only later among gynes. The same conclusion flows from facts already known but hitherto misunderstood and stressed in this paper such as: 1) there are species of Cephalotes with soldiers with incomplete cephalic shield and no gyne shield and other species with complete soldier shield but only incomplete gyne shield; 2) the phragmotic behaviour is exercised by workers and soldiers and not by gynes but its morphological correlate, i.e., the shield-shaped head, occurs among soldiers and gynes and not in workers. These observations prove that the selection pressure for the shield morphology acts on workers and soldiers and not on gynes but its morphological correlate actually appears first in soldiers, later in gynes and never in workers. These data sharply contrast with a worker origin of soldiers and are perfectly consistent with the hypothesis of a separate origin of soldiers directly from gynes.

No abstract

The well known Jaccard's association coefficient has been calculated on perfectly random infinite samples of different n size and a statistical table with the corresponding probability values is presented.

SummaryLast instar larvae of Lasius niger under standard laboratory conditions and abundant food supply feed on conspecific eggs and, if forced to a choice, show a significant statistical preference for trophic versus fertilized eggs (approx. 60 % of the trials observed). On the other hand, they are unable to discriminate between kin and non-kin eggs, both fertilized and trophic. Fertilized eggs killed by freezing and trophic eggs handled in the same way are also selected in a random manner.Last instar larvae of Messor semirufus regularly failed to discriminate in a significant way between trophic and fertilized and between kin and non-kin eggs.Substantial experimental evidence confirms that larvae of both these species -as already suggested in the literature for other ants-rely on trophic eggs as an essential component of their diet in order to be able to develop. Additionally, L. n~ger last instar larvae appear to be able to attack and pierce the egg chorion with their own mandibles, while this capacity is at least very reduced or very rare in M. semirufus. First and second instar larvae of both species never succeeded in piercing the egg membrane alone.These findings imply that the "right" (i.e. trophic) eggs should be presented to the larvae by the workers (i.e. worker discrimination should be assumed) and, at least in the case of young Lasius larvae, and probably for all stages of Messor larvae, the egg membrane must be pierced by the workers in order to allow the larvae to feed. The following evolutionary sequence is suggested to explain the origin of trophic eggs in ants: 1) larval oophagy (obligatory at least for the species founding new colonies in an independent claustral manner), 2) generalized facultative or obligatory larval oophagy for larvae of all colonial stages, 3) production of trophic eggs by the queen(s) and/or workers in order to avoid cannibalism of nestmates.Lack of discrimination or weak discrimination capacity between trophic and fertilized eggs and the consequent larval cannibalism in form of oophagy, as demonstrated in this paper, is suggested to explain age segregation among eggs and larvae from workers, a widespread phenomenon in ants which must have been selected to avoid the oophagy of viable eggs.

No abstract

Abstract. The higher phylogeny of the Formicidae was analysed using 68 characters and 19 taxa: the 14 currently recognized ant subfamilies plus 5 potentially critical infrasubfamilial taxa. The results justified the recognition of 3 additional subfamilies: Aenictogitoninae Ashmead (new status), Apomyrminae Dlussky & Fedoseeva (new status), and Leptanilloidinae Bolton (new subfamily). A second analysis on these better delimited 17 subfamilies resulted in 24 equally most parsimonious trees. All trees showed a basal division of extant Formicidae into two groups, the first containing (Myrmicinae, Pseudomyrmecinae, Nothomyrmeciinae, Myrmeciinae, Formicinae, Dolichoderinae, Aneuretinae) and the second the remaining subfamilies. Clades appearing within these groups included the Cerapachyinae plus ‘army ants’, the Nothomyrmeciinae plus Myrmeciinae, the ‘formicoid’ subfamilies (Aneuretinae + Dolichoderinae + Formicinae), and the Old World army ants (Aenictinae + Aenictogitoninae + Doryline), but relationships within the last two groups were not resolved, and the relative positions of the Apomyrminae, Leptanillinae and Ponerinae remained ambiguous. Moreover, a bootstrap analysis produced a consensus tree in which all branches were represented in proportions much lower than 95%. A reconstruction of the ground plan of the Formicidae indicated that the most specialized of all recent ants are the members of the subfamily Dorylinae and the least specialized ones are the monotypic Apomyrminae.