106 research outputs found
The Formation of Collective Silk Balls in the Spider Mite Tetranychus urticae Koch
Get PDFTetranychus urticae is a phytophagous mite that forms colonies of several thousand individuals. These mites construct a common web to protect the colony. When plants become overcrowded and food resources become scarce, individuals gather at the plant apex to form a ball composed of mites and their silk threads. This ball is a structure facilitating group dispersal by wind or animal transport. Until now, no quantitative study had been done on this collective form of migration. This is the first attempt to understand the mechanisms that underlie the emergence and growth of the ball. We studied this collective behaviour under laboratory conditions on standardized infested plants. Our results show that the collective displacement and the formation of balls result from a recruitment process: by depositing silk threads on their way up to the plant apex, mites favour and amplify the recruitment toward the balls. A critical threshold (quorum response) in the cumulative flow of mites must be reached to observe the emergence of a ball. At the beginning of the balls formation, mites form an aggregate. After 24 hours, the aggregated mites are trapped inside the silk balls by the complex network of silk threads and finally die, except for recently arrived individuals. The balls are mainly composed of immature stages. Our study reconstructs the key events that lead to the formation of silk balls. They suggest that the interplay between mites' density, plant morphology and plant density lead to different modes of dispersions (individual or collective) and under what conditions populations might adopt a collective strategy rather than one that is individually oriented. Moreover, our results lead to discuss two aspects of the cooperation and altruism: the importance of Allee effects during colonization of new plants and the importance of the size of a founding group
Les Règles de comportements à l'origine des stratégies alimentaires chez Lasius niger
No full textDoctorat en Sciencesinfo:eu-repo/semantics/nonPublishe
L’intelligence collective chez les insectes sociaux
No full textinfo:eu-repo/semantics/publishedHors série: L'incroyable socialité des animau
Dragline attachment pattern in the neotropical social spider anelosimus eximius (Araneae: Theridiidae)
No full textThe regularity of spiders orb webs has been considered a fascinating natural
wonder by generations of naturalists. Although the majority of spider species
build irregular three-dimensional networks, those who have evolved the two-
dimensional spiral snare have drawn most of the attention (Vollrath, 1988). Even
studies conducted on irregular webs are often explicitly devoted to the search
of similarities with orb webs, resulting from behavioral preadaptations to this
specific design (Eberhard, 1987, 1992).
So the question of the distance between attachment points in an environ-
ment that does not feature intrinsinc regulating properties, like a three-dimen-
sional web or vegetal structure, remains widely open. In the overall context of
swarming in the cooperative spider Anelosimus eximius (Furey et al, in prepa-
ration), our focus was on amplification mechanisms involved in group cohesion
and coordination of several individuals' activities. From these observations, it
appears that dragline attachment pattern has a direct influence on network design,
and consequently on the population transfer's dynamics, which is confirmed by
theoretical projections about the efficiency of silk-mediated exploratory recruit-
ment (Saffre et al, 1997, in press)
Triggering and persistence of trail-laying in foragers of the ant Lasius niger.
No full textCI:2.04info:eu-repo/semantics/publishe
Recruitment process during migration in Dermatophagoides pteronyssinus
No full textinfo:eu-repo/semantics/nonPublishe
Dragline attachment pattern in the neotropical social spider Anelosimus eximius (Araneae: Theridiidae)
No full textSCOPUS: ar.jinfo:eu-repo/semantics/publishe
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