Influence of the Number of Queens on Nest Establishment: Native and Invasive Ant Species

As a critical stage in the life cycle of ant colonies, nest establishment depends on external and internal factors. This study investigates the effect of the number of queens on queen and worker behavior during nest establishment in invasive Argentine ants (Linepitema humile) and native Mediterranean Tapinoma nigerrimum. We set up experimental colonies with the same number of workers but with one or six queens. At different time points, we recorded the positions of queens and workers inside and outside the nest. Our results highlight the influence of the number of queens on the position of queens and workers with between-species differences. Queens of both species entered the nests more quickly when there were six queens. During nest establishment, more workers were inside nests with six queens for both species, with this effect being greater for T. nigerrimum. Once nests were established, fewer workers of both species were engaged in nest maintenance and feeding in nests with six queens; T. nigerrimum had fewer workers engaged in patrolling. These results suggest that the number of queens is a key factor driving queen and worker behavior during and after nest establishment with different species responses.

Effect of Starvation on the Feeding Activity Toward Sugary Food in the Ant Tapinoma nigerrimum (Nylander, 1856)

In this study, we investigated the effect of starvation on the feeding behavior of the ant Tapinoma nigerrimum. In particular, we tested the response of ants that had experienced different levels of starvation, toward sucrose solutions of increasing concentration. As expected, starved ants promptly reacted to the sugary food sources with a higher rate of acceptance as compared to satiated ones. Acceptance increased both with sugar concentration and the length of the starvation period. However, a consistent fraction of the starved ants did not feed on the solutions, suggesting that starvation had different effects on different individuals, even though they all had food ad libitum before the beginning of the tests, had comparable body sizes, and were collected from the same trail. The different acceptance of sugary solutions may be, therefore, merely because ants fed on the experimental food at different times. Interestingly, in all the experimental groups, ants appeared to satiate quickly, irrespective of the solution tested and fasting duration. This would suggest that the rate of ingestion was independent of these factors, a result partially at odds with previous studies. This study is one of the few ones dealing with the behavioral response of an ant species to a famine event.

Additions to the ant fauna (Hymenoptera: Formicidae) of the Maltese Islands

The Maltese Islands are situated in the Central Mediterranean basin having a total land area of c. 316 km2. A diverse ant fauna is present in this archipelago, which is increasingly threatened by habitat degradation and invasion of alien species. The myrmecofauna of the archipelago has received considerable attention by researchers since 1893, bringing the total number to 59 species (Gómez 2017, Salata and Borowiec 2018), 11 of which are non-native. Confirmation of some already reported species, e.g. Messor structor (Latreille, 1798), Tapinoma nigerrimum (Nylander, 1856), Tetramorium caespitum (Linnaeus, 1758), is required in the light of recent taxonomic changes. Based on a critical literature review, older unpublished data (1995–1997) by one of us (DM), and newly collected ant material (mainly between 2015 and 2019) we provide an updated list of 70 ant species from the Maltese Islands. The specimens were collected by different techniques (e.g. direct sampling, sifting, MSS-traps, Malaise traps). Two ant species were recorded for the first time in the Maltese Islands and for five species we provide the first verified records. Seven morphospecies with unspecified taxonomic status were also collected and require further studies.

Ants (Hymenoptera: Formicidae) of San Marino

A recent catalog of the ants of Europe and surrounding areas listed no ants recorded from San Marino. One afternoon of collecting in urban sites of San Marino yielded 23 ant species: Aphaenogaster subterranea, Camponotus aethiops, Camponotus fallax, Camponotus lateralis, Camponotus piceus, Crematogaster scutellaris, Formica cunicularia, Formica gagates, Hypoponera eduardi, Lasius emarginatus, Lasius lasioides, Lasius paralienus, Messor structor, Pheidole pallidula, Plagiolepis pygmaea, Tapinoma nigerrimum s.l., Temnothorax angustulus, Temnothorax flavicornis, Temnothorax italicus, Temnothorax lichtensteini, Temnothorax tergestinus, Temnothorax unifasciatus, and Tetramorium caespitum. Surprisingly, despite collecting in heavily disturbed urban sites, none of the ants known so far from San Marino are exotic to Europe.

Ants (Hymenoptera: Formicidae) and Spiders (Araneae) Co-occurring on the Ground of Vineyards from Douro Demarcated Region

This study, held in vineyards from Douro Demarcated Region, aimed to: a) identify the communities and main functional groups of spiders and ants; b) check patterns of co-occurrence between the two communities; and c) evaluate the impact of ground cover and adjacent non-crop habitats in the proximity of vineyards, on the two communities. Samplings were done using pitfall trapping. Twenty species of ants and 44 species of spiders were identified, which included respectively three and nine Iberian endemic species. Aphaenogaster gibbosa (Latreille 1798), Aphaenogaster iberica Emery 1908, Cataglyphis hispanica (Emery 1906), Cataglyphis iberica (Emery 1906), Messor barbarus (L. 1767) and Tapinoma nigerrimum (Nylander 1856) totalized 71.21% of ants. Alopecosa albofasciata (Brullé 1832), Callilepis concolor Simon 1914, Eratigena feminea Simon 1870, Zodarion alacre (Simon 1870) and Zodarion styliferum (Simon 1870) accounted for 38% of spiders. Abundance of both ant-mimicking and ant-eating spiders were positively correlated with Formicinae, while only ant-eating spiders showed positive correlation with Myrmicinae ants. All genera/ species of ant-associated spider were associated with one or more genera/ specie of ants. The abundance of specialist spiders was higher in areas where abundance of ants was also higher. Sheet web weavers spiders were found to be positively correlated with the percentage of ground cover. The present study a) stresses that vineyard agroecosystem support a rich assemblage of ants and spiders evincing that wine production and species conservation is possible and b) the co-occurrence between some species of this two groups is not determined by random patterns.

Effects of restriction endonucleases on nucleolar organizing regions in the ant Tapinoma nigerrimum

The effects of some restriction endonucleases (REs) on the nucleolar organizing regions and on the genes for ribosomal RNA (rDNA) were analyzed using the nucleolar organizing region of the chromosome 6 of Tapinoma nigerrimum as an experimental model, since, in accordance with previous studies, the genes for ribosomal RNA seem to be present only in this chromosome. In situ non-digestion of the nucleolar organizing region was observed when EcoRI and HindIII were used. However, very evident digestion and partial digestion respectively were observed when HaeIII and Tru9I were used. Southern blot analysis realized on naked DNA digested with the same REs and using rDNA of Drosophila melanogaster as probe showed that there are target sequences for these enzymes in the rDNA. In accordance with the results obtained, the rDNA is poor in EcoRI and HindIII sequences, contains moderate amounts of Tru9I sequences, and is rich in HaeIII sequences. All the data obtained suggest that in the nucleolar organizing region of Tapinoma nigerrimum, the major, if not the only, limiting factor affecting in situ digestion by the REs used is the presence and frequency of their specific restriction targets. Consequently, extraction of DNA from this chromosome region depends on the size of the fragments originated.Key words: chromosome banding, Formicidae, NORs, rDNA, restriction endonucleases.