The world is crowded with different types of complex information – images that can be perceived differently depending on the types of light an animal is capable of perceiving, sounds that can be heard within a certain range of volume, and many more. For predators, this means that searching for prey is like looking for a needle in a haystack. In response to this overload of sensory possibilities, predators have evolved ways to sense their prey more efficiently. One of these methods is the use of search images – pre-encoded visual cues, such as a pattern, that set off alarm signals an organism’s brain that might help them to find prey. In prior studies, mud dauber wasps have been demonstrated to have preference for certain prey over others due to variations in chemical and visual cues. However, an area of study that has not yet been explored is whether specific patterns on the wasp’s prey – spiders – make them more desirable to the wasps. The study conducted by Robledo-Ospina et al. predicted that mud dauber wasps use of search images to find prey, specifically coloration and patterns on the spider’s body that makes them more recognizable to wasps due to pre-existing alertness for these specific patterns. More specifically, they expected prey selection in mud dauber wasps to favor spiders with similar color patterns that could be perceived by the visual system in the wasps.
The species of mud dauber wasp under investigation was Trypoxylon mexicanum, a species that gathers prey and seals it into their nests while they are still under construction. To study the visual preferences of these wasps, Robledo-Ospina et al. collected the contents of nest cells and quantified their contents. Spiders taken from the nests were photographed in two different conditions – one with a filter that blocked both ultraviolet and infrared light, and the other that allowed ultraviolet light to pass through the filter, but blocked infrared light. These images were merged and manipulated so that they were reconstructed in a way that would have been perceived in the way that a similar wasp species could perceive them. In the end, 474 spiders from 65 cells were sampled. Out of these samples, 13 species of spiders were found. For reference, there are 45,000 species of spiders known in the world today (kids.frontiersin.org). The two most abundant spider species were Eustala delasmata and Neoscona arabesca. There were no significant differences between spider color patterns found in the same nest. However, researchers did find that individual wasps had preferences for certain colors and patterns. Experiments also found that when the diversity of spiders increased in a cell, the diversity of their patterns decreased.
Overall, these results indicate that wasps were likely influenced by color pattern in their selection of prey, supporting the hypothesis made by the authors. The wasp’s preference for certain spiders also begins to indicate other strategies they may use to capture their prey. For example, one of the most common spiders found in nest cells was E. delasmata, a nocturnal spider that hides in vegetation during the day without a web. This indicates that the wasp may capture the spider when they are forced to move after the wasp’s wing strikes the web or its antenna meets the spider.
Perhaps the most intriguing part of this article is that individual wasps become ‘experts’ in capturing types of spiders. This is remarkable because it suggests the presence of memory within individual wasps and its use. Though we may never be able to see the world through the eyes of a wasp, it is amazing to consider the similarities and differences of their perception to our own, as search images are tools that we use daily.
Kuntner M and Agnarsson I (2018) Diversity of Tropical Spiders. Front. Young Minds. 6:64. doi: 10.3389/frym.2018.00064
Luis E. Robledo-Ospina, Nathan Morehouse, Federico Escobar, Dinesh Rao, Search image formation for spider prey in a mud dauber wasp., Behavioural Processes, Volume 197, 2022, 104619, ISSN 0376-6357, https://doi.org/10.1016/j.beproc.2022.104619.