Hymenoptera
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The hymenoptera (Hymenoptera) are an order of insects . Like the beetles , the butterflies and the two-winged birds, they form one of the four “megadiverse” insect orders with around 156,000 described species from 132 families . Hymenoptera are because of their importance for plant pollination ( bees ), their density and biomass often not achieved by any other animal group in numerous ecosystems ( ants ) and their large and often population-limiting influence on all other insects ( legumes) a key ecological group of crucial importance for the structure and function of almost all terrestrial ecosystems. There are also numerous other groups with a variety of other specializations. The hymenoptera includes the majority of the eusocial insect species that form insect states.
Naming
The Hymenoptera form one of the seven insect orders that the founder of modern taxonomy, Carl von Linné , introduced in his work Systema Naturae (10th edition). In contrast to most of the other Linnaeus orders, it is still understood today in the same way as it was then. The nomenclature refers to the membranous wings ( ancient Greek ὑμήν Hymen , German , skin ' and ancient Greek πτερόν pteron , German , wings' ), which, however, not themselves peculiarity of the Hymenoptera, but in the same form nearly all winged insects are common. Linnaeus never explained the reason for its name.
Construction of hymenoptera
Hymenoptera are mostly small to medium-sized insects, the largest species such as Pepsis heros (family Pompilidae ) reach about 6.5 cm body length and 10 cm wingspan. The hymenoptera are the smallest winged insects that reach a wingspan of only about 1 mm. The Hymenoptera are endopterygota with track- or made similar larvae, a pupal stage and usually winged imagines . The head of the adults is usually very mobile with a thin neck region (or cervical region) attached to the trunk. The abdomen, however, is closely connected to the thorax in all hymenoptera. The belly plate (sternum / sternite) of the first abdominal segment has always been lost. In the morphologically more original families, which are grouped together as Symphyta, the mostly cylindrical abdomen sits broadly on the thorax. In the waist wasps (Apocrita) the rear end gains mobility through a constriction of the second abdomen segment. Here the first abdominal segment is firmly fused with the thorax, the rest of the abdomen sits on it with a small stalk (usually) formed from the second segment, the petiolus .
wing
The adults have two pairs of wings (i.e. four wings) in all species whose wings are not completely regressed in a secondary manner, the hind wings of which are always much smaller than the fore wings. In flight, the wings are coupled to each other, they are moved in the same direction and work as a unit. Small, hook-shaped bristles ( called hamuli ), which sit on the rear wing and hook into a notch on the folded-over edge of the front wing, serve as the coupling mechanism. The wing veins are greatly modified and reduced compared to the basic plan of the insects, which made it difficult for decades to homologate the veins . While the wings of most insects are divided into concave and convex sections by alternating high or low veins and thus stiffened like corrugated cardboard, in the hymenoptera (with one exception, the subcosta ) all concave veins have been lost. The wings are almost flat. They have several bending lines (flexion lines) where they can be twisted when moving in flight; these lines also cross the veins, where they become visible as a weak zone or interruption. The front edge of the front wing is usually reinforced by a strong peripheral vein. Usually there is a noticeable, mostly dark-colored thickening on the edge in the front third of the wing, the wing mark ( pterostigma ), which stabilizes the flight in the manner of a trim weight. The wing veins in the larger species usually have a number of quite large, closed cells in the front section, the formation, number and location of which are very important for determining families. In the small species the veining is usually more or less reduced, it can be completely absent in the smallest forms. Tiny hairs (microtricha) that reduce air resistance ( riblets ) almost always sit on the wing surface .
The wings of the hymenoptera are propelled by asynchronous flight muscles. This means that the nerve impulses that excite the flight muscles are not synchronized with the wing beats, but occur uncoupled at some point during the flight phase. The frequency of the wing beat is not controlled by neurons, but results from the mechanics and vibration properties of the wings, the wing joint and the thoracic structures that drive and control the wing beat. The flight is therefore more precisely controlled by varying the angle of attack and the stroke amplitude, while the stroke frequency remains almost constant. In relation to their body size, many hymenoptera have a very high flapping frequency with a rather low amplitude (around 90 ° deflection). As a result, they are often very good pilots with high maneuverability. Many species of bees can hover on the spot in rapid soaring flight .
In the resting position, the wings of the hymenoptera are folded over each other and carried flat on the back. The hind wings, in some groups also the fore wings, are sometimes folded in to reduce the area. In the Symphyta, they are fixed with a Velcro fastener by rough fields on the upper side of the thorax (called Cenchri), which intervene in the roughening of the wing surface. The wings are often crystal clear, but they can often be smoky or dark, more rarely colorful, sometimes even shimmering metallic.
Ovipositor and sting
The female hymenoptera are the only animals within the holometabolic insects to have a laying tube ( ovipositor ). The structure of the ovipositor corresponds to that of numerous groups of the more primitive hemimetabolic insects, e.g. B. that of the grasshoppers, it is therefore called orthopteroid . In fact, its components can be homologated with the laying pipe of the primarily wingless fish . It is therefore not a novelty of the hymenoptera, but inherited from their ancestors, while in the other holometabola it has been receded secondarily ( plesiomorphism ). The ovipositor is present in almost all hymenoptera, but is often retracted inside the body in a prickly chamber and is not immediately visible when at rest. Most plant wasps have a saw blade shape and are used to sink the eggs into plant tissue. In the Legims it is modified many times, but often very thin, it is mostly used to deposit an egg in other arthropods, in which the larva then develops as a parasitoid. In the Aculeata , the ovipositor has been transformed into a defensive spike .
The ovipositor is formed from the back plate (tergum) of the ninth abdominal segment and various attachments that have emerged from the extremities. These are known as gonocoxites and gonapophyses, often more neutral as valvifer and valven (or valvulae). The exit of the internal sexual organs, the gonopore, is on the abdomen between the gonocoxites. The actual ovipositor consists of three pairs of elongated appendages (which can be fused to different extents). The first and second blades form the actual laying drill. As a rule, the two pairs are folded together so that they hang together but can be moved against each other. During the act of pricking, both pairs are moved back and forth at high speed and dig themselves into the substrate, usually facilitated by teeth or barbs. The third blades form a sheath or sheath in which the ovipositor is encased in the rest position. All valves are pervaded by nerves and have numerous sensory hairs.
In hymenoptera there are two glands connected to the ovipositor. In the larger venomous gland, the glandular tubes open into a large cavity that continues in a channel inside the piercing bristles. The secretion is used by the plant wasps as a lubricant or putty for the eggs. In the Legims and Aculeata it is used as a poison, primarily to paralyze hosts for oviposition or prey animals. It is also used for defense in all species where the stinging bristles and the muscles allow it. The second, smaller glands are called Dufour's glands. Their function has not been clarified in all cases. With the ants, they give off an alarm pheromone .
Head and mouthparts
Hymenoptera have mouthparts that are usually adapted to varying degrees to a licking or sucking diet, especially nectar and sugary juices. These usually consist of the intergrown labium and maxilla, which act as a functional unit and which form a structure known as the labiomaxillary complex. In combination with this, they almost always have normal, biting-chewing mandibles. However, these are rarely used directly for nutrition. They have been modified for a variety of other purposes, including freeing up quarters and doll covers and building nests.
In the labiomaxillary complex, the base of the labium is not firmly attached to the head capsule, but to the maxillae. The entire structure can be pre-stretched out of the head capsule by tilting it forward. When stretched out, the labium can move back and forth. The loading of the labium (glossae and Paraglossae), collectively referred Ligula (lat. Ligula "tip"), usually have a hairy surface that can lap up liquids in the movement and move to the mouth opening. This type of nutrition is realized in most hymenoptera, both in the herbivorous Symphyta and in the legims with parasitoid larval development. Most of the Apocrita, which hunt arthropods to feed the larvae, also use them for their own metabolism. The structure of the nectar- and pollen-eating bees, even in the larval stage, is elongated and transformed into a real proboscis that can reach nectar hidden in long flower tubes. The proboscis of the long-proboscis species of bees (e.g. honeybees) include the galeae of the maxillae and the labial palpitations, which together with the glossae delimit the food duct, in other groups other parts can develop a functionally similar proboscis. With the magnificent bees , the licking movement of the glossae is completely abandoned, the nectar is only sucked up like a pipe.
The antennae of the hymenoptera have the characteristic basic structure of the insect with a shaft (scapus), a reversible link (pedicellus) and an antennae (flagellum). The construction of the sensor has been modified in many ways and is highly characteristic of different families. The number of whip limbs can range from one (e.g. Argidae) to more than fifty (some Ichneumonidae). Very often both the number of flagella as well as their shape is sex-specific, the males often have one more flagellum than the females. Sometimes the flagellum limbs are only enlarged in the form of teeth or lamellae in the males. The antennae can be widened club-shaped towards the tip in both sexes, or only in females. In many hymenoptera the shaft link is greatly elongated, in many cases the rest of the antennae is attached to it at a clear angle (kneeling antennae). The surface of the antennae flagella has numerous sensillae that serve as mechanoreceptors and chemoreceptors. In many cases, they are primarily used in females to search for the egg-laying site (food plant or host), in males to search for females, who are often recognized by means of species-specific pheromones. A typical type of sensilla are wide, plate-shaped sensilla (sensilla placodea). The antennae of the males very often also carry glands that play a role in gender recognition and mating.
Larvae
The shape of the larvae in the hymenoptera is often modified due to the different way of life. The larvae of the morphologically more original plant wasps are mostly herbivorous so-called anal caterpillars , similar to the caterpillars of butterflies . Other plant wasps drill into wood or plant stems, they have mostly regressed their legs and show other transformations. The larvae of the Legims (and the Orussidae family related to them ) show numerous reductions due to their parasitic way of life, especially of the extremities and sensory organs. Typically, they are legless (apod), maggot-like larvae, which, with the exception of the head capsule, are only softly sclerotized and mostly white in color. The larvae of the Aculeata correspond in their physique to those of the Legims.
The larvae of the hymenoptera consist of a mostly round or oval head capsule, three trunk and ten abdomen segments, which are often also secondary curled. The chewing mouthparts sit on the head, usually pointing downwards (or slightly backwards). The strongest mouth parts are almost always the mandibles, which can be stocky and toothed or long and sickle-shaped. On the side of the head in the more original forms there is a larval eye (called stemma or ocularium), of which only a single lens can be seen externally. The eye is regressed in boring, parasitic or nesting species. On the side of the head there is a pair of antennas that vary in length, but are almost always quite short. In the spun sawfly they reach about half the length of the head capsule and consist of seven segments. In most hymenoptera the antennae are strongly regressed and consist of a segment that is often barely recognizable. With multi-link antennas, the links usually become noticeably smaller towards the tip. The trunk of the hymenoptera larvae consists of three very similar segments. The free-living Symphyta each have a pair of short pairs of legs, which in the basic plan consist of five segments with a claw at the end, but are often partially or completely reduced. In the free-living plant wasp larvae, short, weakly sclerotized one or two-limbed pairs of legs sit on the abdomen; in the Xyelidae these are located on all abdominal segments, in most sawfly larvae on segments two to seven or two to eight and on the tenth (last) segment.
Most hymenoptera larvae can secrete silk threads made of proteins from glands that open out on the mouth parts (at the labium). In most groups, the last larval stage spins a cocoon out of it, in which pupation then takes place. However, some plant wasps spin protective larval webs in which they live.
Way of life
The hymenoptera are characterized by an unusual variety of special adaptations in the way of life. In particular, the nutrition of the larvae has been modified, while the adults live predominantly on sugary juices such as nectar, and in some groups also pollen (occasionally there is no more food intake at all). In the groups whose larvae are provided with insect food by the mother or who lay their eggs as parasitoids to develop in other arthropods, the adults have often at least partially switched to predatory diets. Many parasitoid wasps also feed at least partially on the haemolymph of their host species, which they cover with eggs. The ants are of particular importance as predators in many terrestrial habitats; the driver ants are a particularly impressive example . The social wasps , which also act ecologically as predators in many habitats in Central Europe, use their prey almost exclusively to feed the larvae and almost only ingest sugary liquids for themselves, as is usual with hymenoptera. Some sawfly (Tenthredinidae) also feed predatory as adults.
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In the original groups of hymenoptera, which are grouped together as plant wasps, the larvae mainly feed on plants (phytophag). A variety of species use leaves from tree species or herbaceous plants. Some species mine in leaves or stems. Some groups, e.g. B. the wood wasps have switched to wood as a food base. In doing so, they do not feed on the wood itself, but cultivate wood-degrading fungi, which represent their actual nutritional basis. Perhaps only once, with the common ancestor of the Orussidae and Apocrita, there was a change to other arthropods as food. The larvae do not hunt prey, but instead feed on a single individual who is initially left alive, but in the end is usually killed. This parasitoid way of life is therefore a hybrid of real parasites and predators. Most of the original species feed on their host from the outside, which is paralyzed and usually quickly killed (idiobionte parasitoids). In many lines of development, however, the larvae went independently of one another to develop inside the host, which remains mobile and can continue to grow (coinobiont parasitoids). Thousands of species are parasitoids from other parasitoids (hyperparasitoids). Some lines of development within Apocrita have later reverted to a phytophagous diet, e.g. B. the gall wasps and some wood wasps . In many groups of the hymenoptera (Aculeata) with weir stingers, which developed from parasitoid legumes, the original parasitoid way of life was retained. Many Vespoidea and Apoidea , however, have completely different diets.
Since the larvae of the hymenoptera are in most cases only slightly mobile, care for the brood plays a very special role in the order. In almost all cases the mother is the caring part, only in very rare exceptional cases both sexes. The females almost always spend a lot of time and care when laying eggs. The eggs usually have to be placed directly in a suitable food substrate, as the larva would hardly be able to make subsequent corrections. Wood wasps and other species that dig into plants usually sink their eggs deep into the wood. Parasitoids normally lay their egg directly in the future host, more rarely and only next to it in immobile hosts (there are exceptions, e.g. the Trigonalidae ). With the Aculeata, the female has generally switched to not leaving the food animals for their offspring at the place where they were found, but rather to transport them to a protected nest. In many lines of development, the larva is provided not only with one, but with many prey organisms (as is the case with the parasitoids). However, quite a few relatives have developed into kleptoparasites that use the provisions gathered by other species for their own offspring. In the case of bees (and a few species from other lines of development), the nest with the larva is no longer provided with arthropods, but with collected pollen.
Many hymenoptera from the most varied lines of development have come to the fact that several animals live together and coordinate their behavior through signal exchange, i.e. that is, they develop social behaviors. In the spider sawfly , many Pergidae and some other groups, the larvae live together in large groups, the feeding behavior, often also the pupation, are coordinated with one another. With parasitoids, numerous larvae often live in the same host ( gregarous parasitoids). In some cases it even happens that some larvae no longer develop themselves, but only defend their siblings (against other parasitoid larvae in the same host); these often also have peculiarities in physique ( box formation ). State-forming insects are common among the hymenoptera . This is facilitated by the haplodiploid sex determination in the order: the males develop parthenogenetically from non-fertilized eggs, while females hatch from fertilized eggs. As a result, the female offspring are particularly closely related to one another, which enables them to increase their inclusive fitness with the support of their sisters . A long underestimated role in the development of eusocial behavior was also played by the fact that living together in a nest in which a lot of work has already been invested always promotes social behavior.
Defense sting and sting of waist wasps
Many apocrita is ovipositor converted into a military sting. They are then called - in contrast to the Legimmen (Terebrantia) - also Stechimmen (Aculeata). They include ants, wasps and real bees (especially honey bees and bumblebees ).
Wehrimmen females can sting by inserting their sting into the victim's skin and pumping poison from a poison gland into the victim through the sting .
- Wasps (including hornets) then pull the stinger out again.
- Honey bees leave it behind in the skin, but only when stinging warm-blooded animals .
Ants with regressed weir sting, e.g. B. scale ants (Formicinae), can also fight back or attack,
- by injecting their poison from a certain distance (e.g. into the eyes of the prey)
- or by first biting their jaws and then injecting into the wound.
Hymenoptera usually sting people in self-defense, mostly to defend their nest and as a direct defensive response. To avoid stings, you should stay within 4 meters of their nests, only move around them calmly and not hit at flying wasps or bees. With the first bites, a quick escape is advisable because the scent can summon more animals.
The risk of stings is often overestimated (see also insect sting , bee venom , hornet venom and insect venom allergy ):
- Individual stitches are painful, but usually harmless, provided the swelling does not hinder breathing.
- In allergy sufferers , however, a single bite can cause severe symptoms.
- Insect bites are very rare for humans.
Economical meaning
As a pollinator and producer of honey, honey bees have traditionally been of great economic and cultural importance. Today, bumblebees are also used commercially for pollination, e.g. B. for pollination of tomatoes in greenhouses. Various types of parasitic wasps are bred and sold for biological pest control. The importance of ants, wasps and parasitic wasps in the ecological balance is immense, but it can hardly be quantified.
Systematics of the hymenoptera
The hymenoptera are divided into the following groups:
- Subordination plant wasps (Symphyta); not a natural group ( monophylum ), but a combination of several lines of development
- Subordination waist wasps (Apocrita); all species show a characteristic constriction of the abdomen
- Partial order Legimmen (Terebrantia)
- Partial order Stechimmen (Aculeata)
The representation under the systematics of the hymenoptera shows the most important families, the views of different authors regarding the systematic classification differ, however, so a classification is given that most closely corresponds to the consensus.
Web links
- private homepage with current reports and forums
- The wild bees and wasps of Schleswig-Holstein - Red List 2001 with explanations, (PDF, 1.35 MB)
- Hymenoptera of Africa and Madagascar (in English)
Individual evidence
- ↑ Aguiar, AP; Deans, AR; Engel, MS; Forshage, M .; Huber, J .; Jennings, JT; Johnson, NF; Lelej, AS; Longino, JT; Lohrmann, V .; Mikó, I .; Ohl, M .; Rasmussen, C .; Taeger, A .; Yu, DS 2013: Order Hymenoptera. In: Zhang, Z.-Q. (Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013). Zootaxa 3703: 51-62. doi: 10.11646 / zootaxa.3703.1.12 PDF
- ^ Carl von Linné : Systema Naturae - Digitized version
- ↑ Christopher Aurivillius : Carl von Linné as an entomologist. Jena (Gustav Fischer Verlag) 1909.
- ^ WRM Mason (1986): Standard drawing conventions and definitions for venational and other features of wings of Hymenoptera. Proceedings of the Entomological Society of Washington 88: 1-7.
- ↑ Douglas L. Altshuler, William B. Dickson, Jason T. Vance, Stephen P. Roberts, Michael H. Dickinson (2005): Short-amplitude high-frequency wing strokes determine the aerodynamics of honeybee flight. Proceedings of the National Academy of Sciences USA 102 (50): 18213-18218. doi : 10.1073 / pnas.0506590102
- ↑ Lars Vilhelmsen (2000): The ovipositor apparatus of basal Hymenoptera (Insecta): phylogenetic implications and functional morphology. Zoologica Scripta 29: 319-345.
- ^ GRE Scudder (1961): The comparative morphology of the insect ovipositor. Transactions of the Royal Entomological Society of London, 113: 25-40.
- ↑ Harald W. Krenn, John D. Plant, Nikolaus U. Szucsich (2005): Mouthparts of flower-visiting insects. Arthropod Structure & Development 34: 1-40. doi : 10.1016 / j.asd.2004.10.002
- ↑ Mark Jervis (1998): Functional and evolutionary aspects of mouthpart structure in parasitoid wasps. Biological Journal of the Linnean Society Volume 63, Issue 4: 461-493. doi : 10.1111 / j.1095-8312.1998.tb00326.x
- ↑ Mark Jervis & Lars Vilhelmsen (2000): Mouthpart evolution in adults of the basal, 'symphytan', hymenopteran lineages. Biological Journal of the Linnean Society Volume 70, Issue 1: 121-146. doi : 10.1111 / j.1095-8312.2000.tb00204.x
- ^ Joan van Baaren, Guy Boivin, Delphine Bourdais, Olivier Roux (2007): Antennal sensilla of hymenopteran parasitic wasps: variations linked to host exploitation behavior. In: A. Méndez-Vilas & J. Díaz (Editors): Modern Research and Educational Topics in Microscopy Vol 1. download (PDF; 2.5 MB)
- ↑ Roberto Romani, Nunzio Isidoro, Paola Riolo, Ferdinando Bin (2003): Antennal glands in male bees: structures for sexual communication by pheromones? Apidologie 34: 603-610 doi : 10.1051 / apido: 2003053
- ↑ MA Jervis, NAC Kidd (1986): Host feeding strategies in Hymenopteran parasitoids. Biological Reviews 61: 395-434. doi : 10.1111 / j.1469-185X.1986.tb00660.x
- ↑ Gabriel AR Melo, Marcel G. Hermes, Bolivar R. Garcete-Barrett: Origin and occurrence of predation among Hymenoptera: A phylogenetic perspective. In: Carlo Polidori (editor): Predation in the Hymenoptera: An Evolutionary Perspective. Transworld Research Network, 2011: 1-22, ISBN 978-81-7895-530-8
- ↑ YP Cruz (1981): A sterile defender morph in a polyembryonic hymenopterous parasite. Nature 294: 446-447.