Bicyclus anynana

The squinting bush brown has been known to participate in the phenomena of mud puddling. This is a specific type of feeding pattern where the butterfly will take up nutrients and sodium through the aggregating on the mud or dung.[18] However, this behavior is only seen in males.[18] Females that have mated with males who have been puddling experience no significant reproductive benefit due to their mate's puddling.[18]

Common emigrant butterflies mud-puddling

Courtship rate plasticity is a change in the rate of stereotypical courtship behavior changes when faced with different environmental factors, such as temperature.[9] Male courtship rates of the squinting bush brown butterfly exhibit a degree of plasticity. Studies have shown that these butterflies will change their courtship rate depending on temperatures throughout their larval stage into their adult stage.[9]

Researchers investigated the critical period for courtship rate plasticity to determine whether or not it differed from the critical period for wing pattern plasticity, which had already been established as the final larval instar.[9] In the squinting bush brown butterfly, high temperatures of around 27 degrees Celsius led to increased courtship by males, but low temperatures of 17 degrees Celsius led to males courting females at a much lower rate.[19] This courtship rate plasticity of the butterflies demonstrates their active adaptation to the current environment.[19]

This change in courtship rate, however, only occurs when the squinting bush brown butterfly is exposed to different temperatures at particular life stages: the temperature individuals experiences during their pupal stage and during adulthood changes male courtship rate while the temperature they experience during the larval stages has no effect.[9] Researchers predict that temperature as an adult has an effect because behavioral plasticity extends throughout development into adulthood. An alternate hypothesis is that adults are affected by temperature as it impacts their movement; this would explain why this study found the same differences in courtship rate when comparing organisms that developed differently but had the same adult conditions.[10]

Researchers at Yale University have discovered that the temperature at which the larvae are raised has an effect on the imago's sexual behaviour.[10] Females raised in a cooler environment are more likely to actively court male butterflies. In a warmer environment, the male butterflies traditionally take on the active role in courtship.[10]

In the squinting bush brown butterfly, there has been a peculiar trend in terms of the mating males: older males seem to have a distinct mating advantage.[8] There are two leading theories on why this may be happening. First older males may be more aggressive in mating, simply because they have a much more limited time in which they can mate. Also there may be preferential treatment of older males by female butterflies.[8] The older males must have some good genes, because they were able to survive for this long, so females choose to mate with them to pass on the good genes to their offspring. In addition to both of these hypotheses, older males were found to have much larger spermatophores, allowing their sperm to outcompete younger male butterflies.[8]

Squinting bush browns are one of the first instances of insects severely affected by inbreeding. There is a large drop in the number of eggs that hatch when the butterflies interbreed. In addition to this the number of adults born from inbreeding have a high probability of being crippled and having low fecundity.[18]

Females have also been known to choose a mate depending on their eyespots.[5] In particular, on how large and bright the UV reflective pupils in their eyespots are. Pupils that are either too large or seem to be too small are selected against, in a process known as stabilizing selection.[5] Researchers hypothesize that female selection rather than predator avoidance has accounted for this stabilizing effect.[5]

As is common with a wide variety of lepidopterans, eyespots located on the wings are a common defensive mechanism for the squinting bush brown.[11] There are two predominant theories on why these eyespots have evolved. The first one is the large eyespots look similar to the eyes of predator's adversary. This temporarily surprises the predator allowing the butterfly to escape. A second potential benefit is that peripheral eye spots bring attention to non-essential body parts.[11] The bird will be more likely to attack the wings, as opposed to the body. More often than not, if the first predator strike fails the butterfly will be likely to escape.[11] These eyespots are most effective against the most common of the bush brown's predators, birds.[10]

In particular it has a seasonal variation in the size of its eyespots.[7] During the African wet season, they have large apparent eye spots, whereas in the dry season, they have vastly reduced eye spots. Larvae growing in the dry season have characteristics of the wet season butterflies and larvae produced in the wet season have phenotypic traits resembling butterflies of the dry season.[19] This adaptive strategy has evolved because it is better to be inconspicuous during the dry season. They can blend in with the brown surroundings.[19] During the wet season, there is a large increase in vegetation, so the eyespots are useful in distracting predators.[6]