Mutillidae | |
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Dasymutilla sp. | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Insecta |
Order: | Hymenoptera |
Superfamily: | Pompiloidea |
Family: | Mutillidae Latreille, 1802 |
Subfamilies | |
Mutillinae Contents |
The Mutillidae are a family of more than 7,000 species of wasps whose wingless females resemble large, hairy ants. Their common name velvet ant refers to their resemblance to an ant, and their dense pile of hair, which most often is bright scarlet or orange, but may also be black, white, silver, or gold. Their bright colors serve as aposematic signals. They are known for their extremely painful stings, (the sting of the species Dasymutilla klugii rated a 3 on the Schmidt pain index and lasts up to 30 minutes [1] ), and has resulted in the common name "cow killer" or "cow ant" being applied to the species Dasymutilla occidentalis. [2] However, mutillids are not aggressive and sting only in defense. In addition, the actual toxicity of their venom is much lower than that of honey bees or harvester ants. [3] Unlike true ants, they are solitary, and lack complex social systems. [4]
Mutillidae can be found worldwide with about 230 genera or subgenera and around 8,000 species worldwide. Over 400 species occur in the North American Southwest. [5]
North American Mutillidae have eight phenotypically distinct and geographically limited Müllerian mimicry rings (Desert, Eastern, Madrean, Texan, Red-headed Timulla, Black-headed Timulla, Tropical, and Western) making up one of the largest Müllerian mimicry complexes on the planet. [6] These mimicry rings are the result of repeated convergent evolution of aposematic traits between co-occurring velvet ant species, rather than shared phylogenetic history. [7] Through the evolution of aposematic traits in velvet ant species in the same ring, local predators have learned to avoid these well-defended wasps.
The exoskeleton of all velvet ants is unusually tough (to the point that some entomologists have reported difficulty piercing them with steel pins when attempting to mount them for display in cabinets).[ citation needed ] This characteristic allows them to successfully invade the nests of their prey and also helps them retain moisture. Mutillids exhibit extreme sexual dimorphism. As in some related families in the Vespoidea, males have wings, but females are wingless. The males and females are so distinct in their morphology that entomologists often find it very hard to determine whether a given male and female belong to the same species, unless they are captured while mating. [8] In some species, the male carries the smaller female aloft while mating, which is also seen in the related family Thynnidae.
As is the case for all aculeates, only female mutillids are capable of inflicting a sting. The stinger is a modified female organ called an ovipositor, which is unusually long and maneuverable in mutillids. In both sexes, a structure called a stridulitrum on the metasoma is used to produce a squeaking or chirping sound when alarmed. Both sexes of mutillids also bear hair-lined grooves on the side of the metasoma called felt lines. Only two other vespoid families (Bradynobaenidae and Chyphotidae) have felt lines, but the females of these families have a distinct pronotum, with a transverse suture separating it from the mesonotum; in female mutillids, these two thoracic segments are completely fused. Members of the family Myrmosidae, formerly classified as a subfamily of mutillids, also have a distinct pronotum in females, but lack felt lines in both sexes.
Adult mutillids feed on nectar. Although some species are strictly nocturnal, females are often active during the day. Females of Tricholabiodes thisbe are sometimes active up to two hours before sunset. Guido Nonveiller (1963) hypothesized the Mutillidae are generally stenothermic and thermophilic; they may not avoid light, but rather are active during temperatures that usually occur only after sunset.
Predation is one of the strongest forces natural selection uses to drive the evolution of an organism's morphology, physiology, and behavior. [9] [10] [11] During this coevolution, the prey either being consumed by the predator or escaping has resulted in a plethora of impressive defensive strategies in prey species to improve the likelihood of escape. Velvet ants avoid predation using the following defense mechanisms: a venomous sting (if female), aposematic coloration, a stridulatory organ in their abdomen, an alarm secretion from their mandibular gland, and a durable exoskeleton. This array of defenses has contributed to the velvet ants being attributed the title of "the indestructible insect." This title was bestowed on them after experimental interactions between velvet ants and their potential predators that resulted in the survival of the ant and the ultimate avoidance by the predator. [12]
The venom that velvet ants inject through their stinger has an unknown composition. According to one researcher, the painfulness of the sting of Dasymutilla klugii outscored 58 other species of stinging insects tested; the only species this researcher rated as having a more painful sting were the Paraponera clavata (bullet ant), Synoeca septentrionalis (warrior wasp), and Pepsis spp. and Hemipepsis spp. (tarantula hawks). [13] In an experimental setting, only two lizard species (one whiptail and one side-blotched lizard) attacked a velvet ant it was exposed to. [12] In both cases the velvet ants were exhibiting rapid lateral and vertical movements to ward off an attack. Once the attack occurred the velvet ants would immediately sting the lizards. This sting resulted in the dropping of the ants in both cases and avoidance for the remainder of the trial. [14] The side-blotched lizard was found dead in its tank 24 hours later. [12] The side-blotched lizard is a natural predator of velvet ants, while the whiptail is not. [12]
The aposematic coloration of velvet ants often corresponds to a specific Müllerian mimicry ring consisting of dozens of species. This offers protection because many local predators have learned to avoid prey with this same coloration. [6] To test the aposematic coloration on birds, mealworms were painted to resemble a velvet ant. During these trials, none of the painted mealworms were consumed, while all the control mealworms were consumed immediately. [12] However, the painted mealworms were attacked by the birds, but the birds immediately ceased the attack. [12] These experiments provide evidence that the aposematic coloration of velvet ants causes their predators to hesitate, acting as a visual defense mechanism.
The stridulatory organ that velvet ants possess produces an audible squeaking when the abdomen is contracted. [15] This mechanism is an auditory cue warning predators that are about to attack to stay away. In one experiment, every time a shrew got within 1 meter of a velvet ant, the velvet ant would begin stridulating. [14] Stridulations became more frequent as the predator moved closer to the velvet ant, and the shrew never attempted to attack the velvet ant. However, different scenarios with shrews have shown that the velvet ant would also stridulate after the shrew attacked it. Every time this occurred the shrew dropped the wasp. [14]
The exoskeleton of the velvet ant is remarkably strong. It required 11 times more force to crush than that of the honeybee. [15] As well as being durable, the exoskeleton is also round, making it more difficult for predators to pierce it with attempted stings or bites. During all the trials that led to the fracture of a velvet ant's exoskeleton, a total of 4 times resulted in the death of that velvet ant within 24 hours. Aside from protection from predators, the exoskeleton also helps control moisture. [15]
Due to these strong defense mechanisms, local predators generally avoid the velvet ants, so it has been difficult to determine their predators. [12] One study found tropical and subtropical iguanian lizards ( Dactyloidae ) to be a local predator of velvet ants in the Black-headed Timulla and Tropical mimicry rings. [16]
Male mutillids fly in search of females; after mating, the female enters a host insect nest, typically a ground-nesting bee or wasp burrow, and deposits one egg near each larva or pupa. Only a few species are known to parasitize other types of hosts; [17] exceptions include the European velvet ant, Mutilla europaea , one of the only species that attacks social bees (e.g., Bombus ), and the genus Pappognatha , whose hosts are tree-dwelling orchid bees. The mutillid larvae then develop as idiobiont ectoparasitoids, eventually killing their immobile larval/pupal hosts within a week or two. Velvet ants exhibit haplodiploid sex determination, as do other members of the superfamily Vespoidea.
Recent classifications of Vespoidea sensu lato (beginning in 2008) concluded that the family Mutillidae contained one subfamily that was unrelated to the remainder, and this subfamily was removed to form a separate family Myrmosidae. [18] [19]
In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry functions to protect a species from predators, making it an anti-predator adaptation. Mimicry evolves if a receiver perceives the similarity between a mimic and a model and as a result changes its behaviour in a way that provides a selective advantage to the mimic. The resemblances that evolve in mimicry can be visual, acoustic, chemical, tactile, or electric, or combinations of these sensory modalities. Mimicry may be to the advantage of both organisms that share a resemblance, in which case it is a form of mutualism; or mimicry can be to the detriment of one, making it parasitic or competitive. The evolutionary convergence between groups is driven by the selective action of a signal-receiver or dupe. Birds, for example, use sight to identify palatable insects and butterflies, whilst avoiding the noxious ones. Over time, palatable insects may evolve to resemble noxious ones, making them mimics and the noxious ones models. In the case of mutualism, sometimes both groups are referred to as "co-mimics". It is often thought that models must be more abundant than mimics, but this is not so. Mimicry may involve numerous species; many harmless species such as hoverflies are Batesian mimics of strongly defended species such as wasps, while many such well-defended species form Müllerian mimicry rings, all resembling each other. Mimicry between prey species and their predators often involves three or more species.
Wasps in the family Pompilidae are commonly called spider wasps, spider-hunting wasps, or pompilid wasps. The family is cosmopolitan, with some 5,000 species in six subfamilies. Nearly all species are solitary, and most capture and paralyze prey, though members of the subfamily Ceropalinae are kleptoparasites of other pompilids, or ectoparasitoids of living spiders.
Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both. It is named after the English naturalist Henry Walter Bates, who worked on butterflies in the rainforests of Brazil.
Vespoidea is a superfamily of wasps in the order Hymenoptera. Vespoidea includes wasps with a large variety of lifestyles including eusocial, social, and solitary habits, predators, scavengers, parasitoids, and some herbivores.
Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avoiding detection, warding off attack, fighting back, or escaping when caught.
The Schmidt sting pain index is a pain scale rating the relative pain caused by different hymenopteran stings. It is mainly the work of Justin O. Schmidt, who was an entomologist at the Carl Hayden Bee Research Center in Arizona. Schmidt published a number of works on the subject, and claimed to have been stung by the majority of stinging Hymenoptera.
Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Müllerian mimics is that predators only need one unpleasant encounter with one member of a set of Müllerian mimics, and thereafter avoid all similar coloration, whether or not it belongs to the same species as the initial encounter. It is named after the German naturalist Fritz Müller, who first proposed the concept in 1878, supporting his theory with the first mathematical model of frequency-dependent selection, one of the first such models anywhere in biology.
Aposematism is the advertising by an animal, whether terrestrial or marine, to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defenses which make the prey difficult to kill and eat, such as toxicity, venom, foul taste or smell, sharp spines, or aggressive nature. These advertising signals may take the form of conspicuous coloration, sounds, odours, or other perceivable characteristics. Aposematic signals are beneficial for both predator and prey, since both avoid potential harm.
Animal colouration is the general appearance of an animal resulting from the reflection or emission of light from its surfaces. Some animals are brightly coloured, while others are hard to see. In some species, such as the peafowl, the male has strong patterns, conspicuous colours and is iridescent, while the female is far less visible.
Dasymutilla is a wasp genus belonging to the family Mutillidae. Their larvae are external parasites to various types of ground-nesting Hymenoptera. Members of this genus are highly variable in sting intensity, ranging from a 1 (D. thetis) to a 3 in the Schmidt sting pain index.
Dasymutilla gloriosa, sometimes referred to as the thistledown velvet ant, is a member of the genus Dasymutilla. Only females are wingless, as in other mutillids. Compared to other mutillids, it is mid-sized, being larger than some of the smallest known species like Dasymutilla vesta but smaller than some of the largest known species like Dasymutilla klugii. It ranges from Utah, Nevada, California, Arizona, New Mexico, Texas and south into Mexico.
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. The wasps do not constitute a clade, a complete natural group with a single ancestor, as bees and ants are deeply nested within the wasps, having evolved from wasp ancestors. Wasps that are members of the clade Aculeata can sting their prey.
Insects have a wide variety of predators, including birds, reptiles, amphibians, mammals, carnivorous plants, and other arthropods. The great majority (80–99.99%) of individuals born do not survive to reproductive age, with perhaps 50% of this mortality rate attributed to predation. In order to deal with this ongoing escapist battle, insects have evolved a wide range of defense mechanisms. The only restraint on these adaptations is that their cost, in terms of time and energy, does not exceed the benefit that they provide to the organism. The further that a feature tips the balance towards beneficial, the more likely that selection will act upon the trait, passing it down to further generations. The opposite also holds true; defenses that are too costly will have a little chance of being passed down. Examples of defenses that have withstood the test of time include hiding, escape by flight or running, and firmly holding ground to fight as well as producing chemicals and social structures that help prevent predation.
Dasymutilla occidentalis is a species of parasitoid wasp that ranges from Connecticut to Kansas in the north and Florida to Texas in the south. Adults are mostly seen in the summer months.
Mutilla europaea, the large velvet ant, is a species of parasitoid wasps belonging to the family Mutillidae. It is a parasitoid on various species of bumblebees and is found in Europe, Asia, and North Africa.
Hemipepsis ustulata is a species of tarantula hawk wasp native to the Southwestern United States. Tarantula hawks are a large, conspicuous family of long-legged wasps that prey on tarantulas by using their long legs to grapple with their prey and then paralyze them with a powerful sting. They are solitary, displaying lekking territorial behavior in their mating rituals.
Pepsis grossa is a very large species of pepsine spider wasp from the southern part of North America, south to northern South America. It preys on tarantula spiders, giving rise to the name tarantula hawk for the wasps in the genus Pepsis and the related Hemipepsis. Only the females hunt, so only they are capable of delivering a sting, which is considered the second most painful of any insect sting; scoring 4.0 on the Schmidt sting pain index compared to the bullet ant's 4.0+. It is the state insect of New Mexico. The colour morphs are the xanthic orange-winged form and the melanic black winged form. In northern South America, a third form, known as "lygamorphic", has a dark base to the wings which have dark amber median patches and a pale tip.
The Myrmosidae are a small family of wasps very similar to the Mutillidae. As in mutillids, females are flightless, and are kleptoparasites in the nests of fossorial bees and wasps.
Euspinolia militaris is a species of wasp in the family Mutillidae. Though it is a wingless wasp, it has sometimes been referred to by the name panda ant.
Pompiloidea is a superfamily that includes spider wasps and velvet ants, among others, in the order Hymenoptera. There are 4 families in Pompiloidea.