Towards Comparative Modelling

In the following subchapter, I will illustrate the proposed research method by analysing two well-known mimicry examples in comparison—brood parasitism of the common cuckoo Cuculus canorus on various passerine host species and Lepidoptera eyespots (e.g. eyed hawk-moth Smerinthus ocellatus). Egg mimicry is supported by additional resemblances, as there are correspondences between the behaviour of the cuckoo chicks and the chicks of a particular host species (for example Kilner et al. 1999) and similarities in the appearance of the adult cuckoo and hawk species (Payne 1977: 8). Eyespots are a common feature in animal visual communication systems, found in almost all kinds of ecosystems. This sign type is present on the bodies of organisms living today, as well as in species that were fossilised long ago (Labandeira et al. 2016). In butterflies and moths, eyespots are the most common and best studied in Nymphalidae, but exist widely also in other families (e.g. Saturniidae, Sphingidae) as well as in fish, amphibians and reptiles. The common understanding of the function of the eyespots is the “intimidation” hypothesis, according to which the eyespots’ function is to deter predators and prevent an attack. The usual reasoning here is that eyespots deter predators because they represent an imitation of vertebrate eyes: this is the “eye mimicry” hypothesis (Blest 1957, see discussion in Kleisner and Maran 2014). Eyespots have yet other functions such as playing a signalling role in sexual selection. In the butterfly Bicyclus anynana (Nymphalidae), for instance, the dorsal wing pattern is supposed to partake in female mate choice, whereas the ventral pattern serves a camouflaging and/or predator-deflecting role (Brakefield and Reitsma 1991; Stevens 2005).

The two common mimicry systems—egg mimicry of the common cuckoo and Lepidoptera eyespots mimicry—could be compared using the five-stage research model proposed above. Since a longer discussion of the egg mimicry of the common cuckoo was given in the previous subchapter, I will present here a comparison between the two mimicry cases in a concise form (see Table 8.1, Fig. 8.3).

Discussion There are both considerable similarities and differences between the mimicry in brood parasitism and Lepidoptera eyespots. Both mimicry systems rely on visual communication (Table 8.1: 2, 5) and are thus well are accessible to the human Umwelt. This proliferates human interest towards these mimicry systems, but at the same time lays the ground for overinterpretation (this should especially be taken into account in the case of brood parasitism, which is also a common cultural narrative). Easy visual access to mimicry may be a cause for disregarding similarities in other communication modalities (UV, tactile characteristics), that is especially relevant for the egg mimicry system. The regulation in both mimicry systems is similar (3, 4), relying primarily on genetic processes at the population/species level with some input from individual learning and recognition. In the case of brood parasitism (1, 2), the combination of the species involved is more restricted and the participants’ specific behavioural reactions and adaptations are well established (in comparison to eyespots mimicry). This distinction is supported by the two domiTable 8.1 Comparative analysis of mimicry in brood parasitism (e.g. Cuculus canorus) and Lepidoptera eyespots (e.g. Smerinthus ocellatus).

nants in communicative functions (4): the poetic function in brood parasitism and the referential function in the mimicry of eyespots.

From a semiotic perspective, the following differences can be brought out between the two mimicry systems (2, 3): egg mimicry in brood parasitism is

Fig. 8.3 Visual representation of the analysed mimicry systems. Left. Common cuckoo’s (MI) mimicry system: cuckoos’ host species (MO1) and hawks (MO2) act as models. The unbroken arrow lines represent the communicative relation between the model (MO) and the receiver (R) that is exploited by the mimicry system (circular arrow represents autocommunication in the host species). The dashed arrow line represents the deceptive relation between the mimic (MI) and the receiver. The dotted line represents the relation of resemblance between the mimic and the model. Right. Mimicry system of the Lepidoptera eyespots, where a butterfly species acts as the mimic (MI), taking advantage of the communicative relation between owls or small carnivorous mammals (MO) and small insectivorous birds (R). Note that from the perspective of the mimic, both the model and the receiver are not specific species, but rather abstract groups (and therefore blurred in the graph)

detached (the imitating and imitated objects are distinct from the bodies of the participating animals), comparable (objects compared are physically together), and complete (resemblance covers most aspects of a single object). This creates good evolutionary and cognitive preconditions for fine-tuning the mimetic resemblance, recognition mechanisms and behavioural responses of which many examples are known (for example, throwing out eggs that are bigger than eggs in the clutch on average, Marchetti 2000). Lepidoptera eyespot mimicry, on the other hand, is an open mimicry system (1, 2, 3) that takes advantage of the quick communication between the winged organisms and relies on the receivers’ recognition capacity, memory and perception of the eye image. Eyespots mimicry relies upon a broader semiotic convention in an ecosystem about the metonymic relationship between the eye image and an animal who actually has such eyes. The metonymic relation here is that of pars pro toto, a part standing for the whole; therefore, there needs to be a general understanding in an ecosystem that eyes are a sign standing for an animal who is active and potentially dangerous. Eyespot mimicry is much less dependent on the specific receiver species (as there are many of these involved), and rather floats in between the resemblances and meanings shared by the inhabitants of a biological community (see Chap. 11 “From abstract mimicry to ecological code”). The eyespot mimicry system could be considered an open mimicry system (differently from brood parasitism) that can easily incorporate new species and images.

The analysis confirms that both mimicry systems (1) are well-established and complex in the natural world. It further demonstrates that although both resemblances rely on visual communication and have basically the same group—small song birds—functioning as the receiver, the ecological and semiotic characteristics of the mimicry systems observed are very different. Comparative analysis of these two mimicry cases hopefully demonstrates the possibilities of semiotic modelling as a research method. It is a tool for getting a quick overview of the different facets of the observed mimicry cases. Semiotic modelling surpasses the limits of evolutionary understanding of mimicry and allows mimicry to be analysed in relation to and comparison with various behavioural imitations. It helps further to determine the role of human cultural interpretation in mimicry and gives the researcher a selfcritical position for the description. By having a set of different questions as a fixed basis, it also allows comparing mimicry cases that may otherwise be quite difficult to relate to one another.