Nest Defense and Conspecific Enemy Recognition in the Desert Ant Cataglyphis fortis

This study focuses on different factors affecting the level of aggression in the desert ant Cataglyphis fortis. We found that the readiness to fight against conspecific ants was high in ants captured close to the nest entrance (0- and 1-m distances). At a 5-m distance from the nest entrance the level of aggression was significantly lower. As the mean foraging range in desert ants by far exceeds this distance, the present account clearly shows that in C. fortis aggressive behavior is displayed in the context of nest, rather than food-territory defense. In addition, ants were more aggressive against members of a colony with which they had recently exchanged aggressive encounters than against members of a yet unknown colony. This finding is discussed in terms of a learned, enemy-specific label-template recognition proces

Desert ants: is active locomotion a prerequisite for path integration?

Desert ants Cataglyphis fortis have been shown to be able to employ two mechanisms of distance estimation: exploiting both optic flow and proprioceptive information. This study aims at understanding possible interactions between the two possibly redundant mechanisms of distance estimation. We ask whether in Cataglyphis the obviously minor contribution of optic flow would increase or even take over completely if the ants were deprived of reliable proprioceptive information. In various experimental paradigms ants were subjected to passive horizontal displacements during which they perceived optic flow, but were prohibited from active locomotion. The results show that in desert ants active locomotion is essential for providing the ants' odometer and hence its path integrator with the necessary informatio

Moths sense but do not learn flower odors with their proboscis during flower investigation

Insect pollinators, such as the tobacco hawkmoth Manduca sexta, are known for locating flowers and learning floral odors by using their antennae. A recent study revealed, however, that the tobacco hawkmoth additionally possesses olfactory sensilla at the tip of its proboscis. Here, we asked whether this second ‘nose’ of the hawkmoth is involved in odor learning, similar to the antennae. We first show that M. sexta foraging efficiency at Nicotiana attenuata flowers increases with experience. This raises the question whether olfactory learning with the proboscis plays a role during flower handling. By rewarding the moths at an artificial flower, we show that, although moths learn an odor easily when they perceive it with their antennae, experiencing the odor just with the proboscis is not sufficient for odor learning. Furthermore, experiencing the odor with the antennae during training does not affect the behavior of the moths when they later detect the learned odor with the proboscis only. Therefore, there seems to be no cross-talk between the antennae and proboscis, and information learnt by the antennae cannot be retrieved by the proboscis

Acetoin is a key odor for resource location in the giant robber crab Birgus latro

The terrestrial and omnivorous robber crab Birgus latro inhabits islands of the Indian Ocean and the Pacific Ocean. The animals live solitarily but occasionally gather at freshly opened coconuts or fructiferous arenga palms. By analyzing volatiles of coconuts and arenga fruit we identified five compounds, including Acetoin, which are present in both food sources. In a behavioral screen performed in the crabs’ habitat, a beach on Christmas Island, we found that of 15 tested fruit compounds Acetoin was the only volatile eliciting significant attraction. Hence, Acetoin might play a key role in governing the crabs’ aggregation behavior at both food sources

Smells like home: Desert ants, Cataglyphis fortis, use olfactory landmarks to pinpoint the nest

<p>Abstract</p> <p>Background</p> <p><it>Cataglyphis fortis </it>ants forage individually for dead arthropods in the inhospitable salt-pans of Tunisia. Locating the inconspicuous nest after a foraging run of more than 100 meters demands a remarkable orientation capability. As a result of high temperatures and the unpredictable distribution of food, <it>Cataglyphis </it>ants do not lay pheromone trails. Instead, path integration is the fundamental system of long-distance navigation. This system constantly informs a foraging ant about its position relative to the nest. In addition, the ants rely on visual landmarks as geocentric navigational cues to finally pinpoint the nest entrance.</p> <p>Results</p> <p>Apart from the visual cues within the ants' habitat, we found potential olfactory landmark information with different odour blends coupled to various ground structures. Here we show that <it>Cataglyphis </it>ants can use olfactory information in order to locate their nest entrance. Ants were trained to associate their nest entrance with a single odour. In a test situation, they focused their nest search on the position of the training odour but not on the positions of non-training odours. When trained to a single odour, the ants were able to recognise this odour within a mixture of four odours.</p> <p>Conclusion</p> <p>The uniform salt-pans become less homogenous if one takes olfactory landmarks into account. As <it>Cataglyphis </it>ants associate environmental odours with the nest entrance they can be said to use olfactory landmarks in the vicinity of the nest for homing.</p

The olfactory coreceptor IR8a governs larval feces-mediated competition avoidance in a hawkmoth

Finding a suitable oviposition site is a challenging task for a gravid female moth. At the same time, it is of paramount importance considering the limited capability of most caterpillars to relocate to alternative host plants. The hawkmoth, Manduca sexta, oviposits on solanaceous plants. Larvae hatching on a plant that is already attacked by conspecific caterpillars face food competition. Here, we show that feces from conspecific caterpillars are sufficient to deter a female M. sexta from ovipositing on a plant. Furthermore, we not only identify the responsible compound in the feces but also localize the population of sensory neurons that governs the female’s avoidance. Hence, our work increases the understanding of how animals cope with a competitive environment