Evolutionary dynamics shape two passive defensive mechanisms in Neotropical snake radiations

We mapped the distribution of two defensive behaviors (balling and head hiding) of Neotropical snakes to evaluate its distribution in distinct phylogenetic groups. Balling behavior was observed in 58 out of the 167 examined species across seven families. Head hiding was observed in a total of 100 species across nine families. From the high prevalence of balling behavior in basal groups of snakes, such as Anomalepididae, Boidae, Leptotyphlopidae, Tropidophiidae, and Typhlopidae, and the low prevalence among species of recent diversification radiations, such as Elapidae and Viperidae, we suggest that this behavior evolved in basal groups and persisted in some derived taxa. Balling was not observed in association with other defensive strategies, while head hiding can occur in combination with caudal elevation, caudal vibration, and body flattening. Therefore, head hiding, in contrast to balling behavior, presents itself as putatively more flexible, as it should allow for an escalated degree of defensive displays.

Balling Behavior of Selective Laser Melting (SLM) Magnesium Alloy

Macroscopic surface morphology and balling mechanism of AZ61 magnesium alloy prepared by Selective laser melting (SLM) have been investigated. This article studied and analyzed the surface morphology and balling phenomenon of Mg in the laser processing from the aspects of Mg inherent metal properties and laser processing. In terms of laser processing, the results show that, in the direction of increasing scanning speed, the energy density decreases, and the phenomenon of balling and porosity on the surface of the magnesium alloy is serious. When the energy density is 133.9–187.5 J/mm3, balling particles are significantly reduced. It can be seen from the low-magnification SEM image that, even at a scanning speed of 250 mm/s (Ev is 187.5 J/mm3), there are still a few small-sized balling particles on the surface. Therefore, in terms of inherent metal properties, the wettability, capillary instability, thermodynamic, and kinetic analysis of the balling behavior of Mg and other metal (Al, Fe, Cu, Ni, Ti) droplets in the SLM process has been carried out, and the dynamic model of magnesium droplet spreading/solidification was established basic on the result of experiment and metal inherent properties. The results show that SLMed magnesium alloy is a competitive process of melt diffusion and solidification. The final result depends on the intrinsic properties of the magnesium alloy and the applied laser processing parameters. The spreading process of Mg melt is very fast. Although the solidification time of Mg melts changes slowly with the increase of metal droplet temperature, the spreading speed is still very fast due to the low melt density, so the balling phenomenon of SLMed Mg can be controlled to a certain extent. Theoretically calculated, the solidification time of Mg melt droplet is longer than the wetting time at 1173 K (900 °C), so the spreading process is dominant, which can minimize the balling and realize the densification of SLMed Mg. The dynamic spreading of molten pool, the analysis of wetting and solidification process, and the establishment of SLM balling model can provide reference for the design of the SLM forming parameters of Mg and other different metals.

Balling Behavior of Workers Toward Honey Bee Queens Returning from Mating Flights

During natural mating honeybee queens can get lost due to drifting, predators or other cases. In this work, the balling of queens returning from flights by worker bees originating from the same colony was observed. Three subspecies of bees Carniolan, Caucasian and European Black Bee were tested. Research was conducted in both spring and summer, but in the former in newly created colonies, while in the latter in new and earlier used ones. Generally 15.2% of queens were balled and in total 30.2% of queens were lost during mating flights. 269 queens performed 785 mating flights, and 5.2% of those finished with balling. Three times more queens were balled when returning from mating flight rather than orientation flight. Subspecies matches or mismatches of queens and workers in nucleuses did not significantly affect the balling or its frequency. Additionally, no bee subspecies characterized stronger tendencies to ball a queen. Worker bees from newly created nucleuses treated queens similarly to the ones in nucleuses earlier used. However, significantly more queens had been balled during the spring in comparison to summer. There were days with higher balling of queens. During some days the weather was very unstable and unpredictable with such anomalies as heat waves, thunderstorms or sudden drops in insolation. Most of the queens were balled at the entrance while returning from flight and only a few inside the hive. In the research, clear causes of balling were not found, but some factors can be excluded.