Gendernalik 1 Behavior in Insect Mimicry Alex Gendernalik [email protected] Keywords: mimicry, batesian, wasmannian, peckhamian, aggressive, ant, spider, firefly Abstract Arthropods use insect mimicry to gain predatory advantages over other insects in the form of increased resource availability and protection from predators. They do this through several different mechanisms, 4 of which are described in the paper; Batesian, Peckhamian, Wasmannian, and Tephritid mimicry. ‘Mimicry’ includes resemblances in both appearance and behavior. Without mimicry in both appearance and behavior (given both are displayed by the model) the organism will be unsuccessful in mimicking its selected model1. This was shown through Greene and Mather’s research on tephritid flies and salticid spiders. Appearance and behavior must be conspicuous to be detected by the deceived. Photuris fireflys and Portia spiders use aggressive mimcry to lure their prey near to them. Then they capture their prey and enjoy the meal. This type of mimicry is not as common as Batesian mimicry but a very interesting strategy nonetheless. Ants are especially formidable prey. Their defenses are strong and relentless, which keeps them safe from common ant predators (birds, other arthropods, etc.). A successful mimic of an ant would enjoy the same protection from predators. Several different spider families have evolved to do just that. 1. Mimicry, as described in this paper, is developed over the course of thousands of years through the mechanism of natural selection. It is not a choice made by the organism. Gendernalik 2 Introduction Over thousands of years arthropods have developed a practically infinite number of strategies for surviving and reproducing and in doing so they have become the most successful phylum, containing the most successful class; the insects. Every organism in the animal kingdom has evolved to fulfill a particular niche. As organisms speciate and as ecosystems change new niches become available and new species evolve to fill those new niches. No matter how obscure or seemingly insignificant the opportunity, something will evolve to take advantage of the new niche. Interactions between organisms can have infinite numbers of outcomes, which outcome occurs depends on the abilities of each organism. The organisms will evolve until one has an advantage over the other or until they develop a mutually beneficial relationship. Insect mimicry is one of the greatest examples of natural selection. It allows the observer to visualize the available niche and determine what adaptations were necessary to fill that particular niche – you only need to observe the model, the mimic, the predators and their behaviors. Insect mimicry is generally defined as the resemblance to a model through color, pattern, body structure, behavior or any combination of the previous characteristics. All mimics gain some fitness through their mimicry abilities and there are many advantages to mimicking an insect. Mainly, mimics are protected from predators and (or) have the ability to deceive their prey, their mimicry grants them the ability to have more success in capturing prey. Gendernalik 3 Types of Insect Mimicry In this review I will concentrate on implications of behavior in four types of insect mimicry; (1) Batesian mimicry, (2) Peckhamian (aggressive) mimicry, (3) Wasmannian mimicry and (4) Tephritid mimicry2. In Batesian mimicry, described by Henry Walter Bates in 1861, the model is distasteful or venomous and the mimic is not. Predators learn to associate the appearance of the model with unpalatability. Ultimately, the palatable mimic is protected because it resembles the unpalatable model. Aggressive (Peckhamian) mimicry was described by Poulton in 1890; it was Poulton who coined the term ‘Peckhamian’ mimicry because his work was largely based on the observations of E.G. Peckham (Rettenmeyer 1970). Cases of aggressive mimicry involve a harmless looking mimic (resembles the model or another harmless species) that uses its harmless appearance to either lure the prey to within attacking distance or to safely enter the prey’s nest, web, or territory to devour the prey and any resources the prey has collected. In Wasmannian mimicry (described by Eric Wasmann and termed by Rettenmeyer in 1970) the mimic resembles the model in order to enter the models’ territory and either hide among the crowded colony (“schooling” in fish) or feast on the models’ resources. The mimic is not always harmful to the host – they may sure a mutually beneficial relationship 2. Tephritid mimicry has only been termed such by the author for the purposes of this paper. Gendernalik 4 In Tephritid mimcry (unofficially termed by the author for the purposes of this review), described by Eisner, is a unique form of mimicry in which the mimic (fruit fly) resembles its predator (the jumping spider) in order to escape predation by the jumping spider. Mimic Behavior A common perception when one hears the word ‘mimic’, is that of creatures that have evolved to look identical. This is true; most mimics do physically resemble each other. However, the organism also mimics the models behavior. Morphological or structural adaptations are additional to foremost behavioral adaptations (Mayr 1970). This is easy to consider, a population or community of individuals will always adapt or evolve its organism behavior to fit its new niche prior to the evolution of its organism structure. In the examples below, the displayed behavior of the mimic is a “semi” pre- adaptation – the type of behavior (grooming, courtship, time active, etc.) was already in use by the mimic before it evolved into ‘mimicry’ behavior. Mimics tend to display the model’s most conspicuous characteristic (Rettenmeyer 1970). In many insects, the most conspicuous characteristic is their behavior. For example, an ant moves in curious, zig- zag maneuvers as it scans the ground and sky for direction cues – a jumping spider moves in fast, jerky maneuvers as it hunts for prey to pounce on. In fact, these exact conspicuous behaviors are mimicked by other species of jumping spider and flies, respectively. Most insects have very poor eye sight – these insects rely on conspicuous body structures, color patterns and the behavior of their potential prey to identify whether or not their prey is palatable. This suggests that small changes in behavior or body Gendernalik 5 structure/color would be undetectable to most insects - obvious behavior (relative to the observer) and colorful or large body structures are most important in insect mimicry. Tephritid Mimicry Even an insect with extraordinarily acute vision, such as the territorial jumping spider (Salticidae), can be fooled into thinking it’s facing a conspecific by a few cryptic patterns and some confusing behavior exhibited by the mimic. The tephritid fly mimics a jumping spider by raising its wings to reveal salticid leg-resembling patterns, spots on the end of its abdomen mimic the eyes of a salticid jumping spider. The fly also closely mimics the leg waving and jerky movements of a jumping spider by moving its wings up and down and dancing from side to side when disturbed (Mather and Roitberg 1987). A jumping spider displays the same jerky behavior when another salticid enters its territory, likewise, a salticid that wanders into another’s territory will display back before retreating, each encounter usually begins with leg waving and ends with a retreat. A salticidid that encounters a conspecific will usually retreat because the first salticid inhabitant is always dominant – size not being an issue (Mather and Roitberg 1987). Many flies use wing flicking (leg waving to jumping spiders) and wing markings displays, especially common in courtship of tephritids (Greene, Orsak, Whitman 1987). It is possible that the tephritid mimicry of salticids was a small evolutionary step from courtship behavior to salticidid mimicry. In their experiments, Greene, Orsak, and Whitman tested the effects of wing- waving and wing patterns on the behavior of salticid spiders by gluing housefly wings (no leg resembling patterns) on tephritids and releasing a salticid in the same area. In most cases the spider attacked the tephrited with housefly wings despite its defensive Gendernalik 6 display. Likewise in most cases, the spider attacked houseflies that had tephritid wings glued onto them. Mather and Roitberg’s experiments show that tephritid flies require both behavioral and visual mimicry to be effective in deterring salticid spiders. The tephritid fly has evolved to use the territorial displays of jumping spiders to its advantage by mimicking its own predator in order to deter it from attacking, which is a rarely reported case (Mather and Roitberg 1987). Greene, Orsak, and Whitman (1987) postulated that displays of tephritid mimicry of salticids might also deter other common fly predators (other spiders, Assassin bugs, Mantids, and lizards), this theory was proven false when the research team put salticid mimicking tephritid flies in the presence of the aforementioned predators – in almost every case the predator attacked and killed the tephrited fly. Aggressive Mimicry The behavior of the salticid spiders of the genus Portia poses an interesting example of aggressive mimicry. The diet of Portia consists mostly of other spiders and their captures, which is quite unusual as most salcitid spiders prey on insects (Jackson and Pollard 1996). Portia uses a combination of camouflage and aggressive mimicry to fool its prey into believing it is a piece of debris caught in the web and then trick the prey by luring it closer through mimicking web vibrations of ensnared insects. Portia uses its palps, legs, and abdomen to manipulate different vibrations sent through the web – when the resident spider responds to a certain vibration pattern. This behavior is thought to be an adaptation of some grooming behaviors, which closely resembles the insect- mimicking behavior of Portia on resident spider webs. After the resident spider responds to a certain vibration pattern, Portia begins to continuously reproduce that pattern, luring Gendernalik 7 the spider closer.