Alate gyne of the ant Dolichoderus quadripunctatus (L.) (Hymenoptera, Formicidae) follows foraging trail to aphids

The first observation of alate gyne of Dolichoderus quadripunctatus (L.) visiting aphids is described. A gyne walked along a foraging trail to the aphid Panaphis juglandis Goeze colony where it imbibed honeydew excreted on the leaf by the aphids, after which it returned to the trail. This recurred during two more days, always a single alate gyne at a time; hence the total number of gynes, one or more, remained open. The phenomenon, hitherto practically unknown in ants, is presented against the background of the biology of the species and discussed in the context of specific environmental circumstances and the colony dynamics.

State of knowledge of viviparity in Staphylinidae and the evolutionary significance of this phenomenon in Corotoca Schiødte, 1853

Viviparity is characterized by the retention of fertilized eggs in reproductive tract of the female. This condition is very common in vertebrates, but relatively rare in invertebrates, including insects. The present work presents a review on viviparity in Staphylinidae, with special attention on genus Corotoca Schiødte, 1853. The genus is composed by six termitophilous species with neotropical distribution, and together with Spirachtha Schiødte, 1853 are only two genera with species confirmed as viviparous in the family. Some other cases are only supposition. Also, it is presented information and discussion on the life cycle of Corotoca species based on dissection of females in laboratory and field observations. During the dissection of females of four species of Corotoca it was observed that each female carries three eggs at the same time. The embryos present asynchronous development: when one is located at apex of abdomen, the other two are at IV segment, on abdomen curvature. These observations are complementary with those obtained in field observation, when the female deposits a larva outside the nest, on the foraging trail of termite Constrictotermes cyphergaster (Silvestri, 1901). The strategy of Corotoca species focused on the immature as dispersing agent is derived and probably favor the fitnees in relation to a hypothetical condition in which the adult is the dispersive agent.

Run to the nest: A parody on the Iron Maiden song by Corotoca spp. (Coleoptera, Staphylinidae)

Rove beetles belonging to the genus Corotoca (Staphylinidae: Aleocharinae) are termitophiles exclusively found in nests of Constrictotermes (Isoptera: Termitidae). We observed the reproductive behavior of Corotoca melantho and C. fontesi during host (C. cyphergaster) foraging events. The reproductive behaviors of both species are similar. The variables collected for analysis were distance traveled, the time of larval deposition, nest return time, and locomotion speed. The fact that the female stops in the middle of the foraging trail to deposit the larva leads to a discussion of how its physiological or voluntary mechanisms function to determine the correct stopping time and the importance of speed when returning to the nest as a strategy to avoid predation. This study provides new information concerning the life cycle of Corotoca spp., although complete understanding of host-termitophile relationships, their evolutionary history, and the significance of viviparity will require additional studies.

“The road to reproduction”: foraging trails of Constrictotermes cyphergaster (Termitidae: Nasutitermitinae) as maternities for Staphylinidae beetles

Corotoca (Coleoptera: Staphylinidae) beetles are known for their close integration in the nests of the termite Constrictotermes cyphergaster (Termitidae: Nasutitermitinae). Although this relationship is regarded as ancient, many details are still obscure, such as their reproduction and the processes that lead to the dispersal of new beetles. We observed the use of termite foraging trails by Staphylinidae females to deposit and disperse their larvae. We recorded the deposition of larvae of C. melantho, C. fontesi, and C. sp. n. on the dorsal surfaces of termite host workers. The workers continue to follow the foraging trail until the newborn larvae freed themselves and fell into the leaf litter, subsequently burrowing into the ground. Information regarding the life stages of those Staphylinidae larvae outside the termite nest is important to understanding their full lifecycle as those taxa have strong relationships with the nest environment but also require dispersal strategies.

Regulatory mechanism predates the evolution of ant-like swarm intelligence in simulated robots

The evolution of complexity is one of the prime features of life on Earth. Although well accepted as the product of adaptation, the dynamics underlying the evolutionary build-up of complex adaptive systems remains poorly resolved. Using simulated robot swarms that exhibit ant-like group foraging with trail pheromones, we show that their swarm intelligence paradoxically involves regulatory behavior that arises in advance. We focused on a “traffic rule” on their foraging trail as a regulatory trait. We allowed the simulated robot swarms to evolve pheromone responsiveness and behaviors simultaneously. In most cases, the traffic rule, initially arising as selectively neutral component behaviors, assisted the group foraging system to bypass a fitness valley caused by overcrowding on the trail. Our study reveals a hitherto underappreciated role of regulatory mechanisms in the origin of swarm intelligence, as well as highlights the importance of embodiment in the study of their evolution.

Does Atta laevigata (Smith, 1858) act as Solanum lycocarpum seed dispersers?

Ants can act as seed dispersers, modifying their distribution, affecting the reproductive success and the vegetation spatial structure. The leaf-cutting ants function, as dispersers of non-myrmecochorous plants, is little known. This work aimed to evaluate descriptively the Atta laevigata interaction with Solanum lycocarpum diaspores. The observations were carried out, throughout 10 days, in a secondary fragment of Semidecidual Seasonal Forest in Ivinhema, MS. To determine the removal rate, 500 seeds were taken from ripe fruits, dried, labeled and distributed in groups ranged from five to 50 seeds, totaling 100 seeds per foraging trail. Groups of 30 seeds with pulp were also distributed every 1.0 m on the trails. Individuals of different sizes presented different interactions to the fruits and seeds, smaller workers carried pulp or seeds separately, medium workers carried seeds with pulp or cleaned them before carry to the nest and the largest workers carried the seeds to the nest. Atta laevigata acted primarily as predators, with few seeds discarded. Their actions may interfere in the native vegetation regeneration, with a significant role in removing S. lycocarpum seeds, a pioneer species, and in population control for this species by the severe predation of seeds. However, the remaining1.6% intact seeds allows germination, with the A. laevigata acting as a seed dispersers over short distances for this species, favoring the S. lycocarpum dispersion.

Army ants dynamically adjust living bridges in response to a cost–benefit trade-off

The ability of individual animals to create functional structures by joining together is rare and confined to the social insects. Army ants (Eciton) form collective assemblages out of their own bodies to perform a variety of functions that benefit the entire colony. Here we examine ‟bridges” of linked individuals that are constructed to span gaps in the colony’s foraging trail. How these living structures adjust themselves to varied and changing conditions remains poorly understood. Our field experiments show that the ants continuously modify their bridges, such that these structures lengthen, widen, and change position in response to traffic levels and environmental geometry. Ants initiate bridges where their path deviates from their incoming direction and move the bridges over time to create shortcuts over large gaps. The final position of the structure depended on the intensity of the traffic and the extent of path deviation and was influenced by a cost–benefit trade-off at the colony level, where the benefit of increased foraging trail efficiency was balanced by the cost of removing workers from the foraging pool to form the structure. To examine this trade-off, we quantified the geometric relationship between costs and benefits revealed by our experiments. We then constructed a model to determine the bridge location that maximized foraging rate, which qualitatively matched the observed movement of bridges. Our results highlight how animal self-assemblages can be dynamically modified in response to a group-level cost–benefit trade-off, without any individual unit’s having information on global benefits or costs.