1,720,967 research outputs found
Rolling away: a novel context-dependent escape behaviour discovered in ants
No full textFor animals facing dangers, the best option to optimize costs and benefits of defence sometimes may be avoidance. Here we report the discovery of a peculiar strategy adopted by Myrmecina graminicola, a cryptic ant living in forest floor. Experiments showed that when disturbed these ants respond with immobility. However, upon perceiving disturbance but under specific inclinations of the substrate, they shift to an active escaping strategy: rolling away. This is a context-dependent behaviour adopted only in appropriate circumstances. During rolling, the ants assume a ball-like shape using antennae and hind legs to obtain an active movement along a stable trajectory. Finally, we assessed the adaptive value of this strategy measuring its effectiveness in defence against enemies. This is the first example of locomotion by rolling discovered in ants and one of the very few among animals, offering opportunities for multidisciplinary research on the adaptations and biomechanics underlying it
Different nest entrance architecture by Colobopsis and Temnothorax ants colonizing oak galls
No full textGalls are neoformed structures induced on the tissues of a host plant by different organisms, mostly insects. Apart from the inducers, galls can also provide shelter to several different arthropods, referred to as secondary occupants. In certain types of galls, ants are among the prevalent secondary colonizers. This study focuses on oak galls induced by the cynipid wasp Andricus quercustozae and secondarily colonized by two ant species, Colobopsis truncata and Temnothorax italicus. We provide a first characterization of the architectural differences concerning the way they reduce the size of the exit holes excavated by the adult cynipds in order to transform them in their nest entrances. The nest entrance holes differed markedly between the two species in their size and positioning, as well as in the construction material. C. truncata built larger entrance holes with a more central position, apparently facilitating the defensive ability of the phragmotic soldiers, while the smaller nest entrance hole by T. italicus were located in a lateral position. On the other hand, only T. italicus mixed dead insect fragments in the construction material (including the defensive hastisetae of dermestid larvae), probably due to a more insectivorous diet compared to C. truncata
Unlike rolling stones: not every Myrmecina species actively rolls away from danger (Hymenoptera, Formicidae)
Full text linkActively rolling away is a very rare escape strategy in the animal kingdom, which to date has only been documented in a few arthropod and one vertebrate species. One of these arthropods is a West-Palearctic ant, Myrmecina graminicola, which has very recently been demonstrated to actively curb into a ball-like shape rolling away upon disturbance, and to selectively display this behavior only under particular circumstances. We tested whether one of the other three W-Palearctic Myrmecina species, the rare insular endemism M. sicula, exhibited the same behavioral response, using the same experimental approach used for M. graminicola. Our results showed that M. sicula reacted to moderate disturbance by either freezing its body or walking away. Only when the individual lost contact with the substratum, it could curl into a ball-like shape, yet this was significantly less refined than the one displayed by M. graminicola, as the appendages of M. sicula are not tightly kept close to its body. However, M. sicula never performed the active rolling behavior that is readily exhibited by M. graminicola. Ecological, morphological, and phylogenetic constraints may have determined the lack of a developed active rolling escape-strategy in M. sicula. Further investigations are required to assess the presence or absence of this unique behavior across Myrmecina lineages
Tool use in pavement battles between ants: first report of Tetramorium immigrans (Hymenoptera, Formicidae) using soil-dropping as an interference strategy
No full textSoil-dropping is a rarely observed interference behavior so far only documented for six phylogenetically very diverse ant species. Usually, it is employed against rival ant colonies, and may aim to plug their nest entrances to stop their foraging activities. Here, we provide the first testimony of the use of soil dropping by Tetramorium ants against other ant colonies, documenting this behavior for Tetramorium immigrans Santschi, 1927. Workers of a T. immigrans colony approaching the annual nuptial flight were observed dropping over 30 soil fragments into the nest entrance of a Camponotus barbaricus Emery, 1905 colony in Sicily (Italy) during an 80 s observation time. Fragments were all similar in size and averagely about 1.6 times larger than T. immigrans head size, and were dropped in consecutive ways to a rate of 0.7 fragments per second. Tetramorium immigrans is a recently recognized cryptic alien species, highly successful in urban environments, and whose behavioral adaptations are still little known
TRUNK SIZE INFLUENCES SPECIES RICHNESS AND FUNCTIONAL COMPOSITION OF BIOGEOGRAPHICALLY DIFFERENT TREE-VISITING ANT COMMUNITIES IN PEAR ORCHARDS
No full textWe investigated the diversity of ant assemblages visiting pear trees in Italy by comparing two orchards from a northern region with continental climate (Emilia-Romagna) and a southern region with Mediterranean climate (Sicily). Overall we identified 20 ant species belonging to 10 genera and 3 subfamilies. The ant communities of the two sites look significantly different in biogeographic terms, but their functional composition is similar. Moreover, we discovered that both ground and arboreal nesting species richness is positively correlated with the trunk circumference. In particular, arboreal-nesting species are limited to the deadwood richer medium and large trees. Some of the detected ant species may be useful to pest control strategies, and artificial nests may be considered to attract arboreal-nesting species in deadwood-poor trees
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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