Hymenoptera is a large order of

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s, comprising the

sawflies Sawflies are the insects of the suborder Symphyta within the order Hymenoptera, alongside ants, bees, and wasps. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plants where they lay ...

wasp 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. Th ...

s, bees, and

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...

s. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

. Females typically have a special

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...

for inserting eggs into hosts or places that are otherwise inaccessible. This ovipositor is often modified into a stinger. The young develop through

holometabolism Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago (or adult). Holometabolism is a synapomorphic trait of all insects in the superorder Endopterygot ...

(complete

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

)—that is, they have a wormlike larval stage and an inactive pupal stage before they mature.

Etymology

The name Hymenoptera refers to the wings of the insects, but the original derivation is ambiguous. All references agree that the derivation involves the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

πτερόν (''pteron'') for wing. The Ancient Greek ὑμήν (''hymen'') for membrane provides a plausible

etymology Etymology ()The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the Phonological chan ...

for the term because species in this order have membranous wings. However, a key characteristic of this order is that the

hindwings Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hindw ...

are connected to the

forewings Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hindwi ...

by a series of hooks. Thus, another plausible etymology involves

Hymen The hymen is a thin piece of mucosal tissue that surrounds or partially covers the external vaginal opening. It forms part of the vulva, or external genitalia, and is similar in structure to the vagina. In children, a common appearance of the h ...

, the Ancient Greek god of marriage, as these insects have married wings in flight. Another suggestion for the inclusion of Hymen is the myth of

Melissa Melissa is a female given name. The name comes from the Greek word μέλισσα (''mélissa''), "bee", which in turn comes from μέλι (''meli''), "honey". In Hittite, ''melit'' signifies "honey". ''Melissa'' also refers to the plant ''Me ...

, a nymph with a prominent role at the wedding of Zeus.

Evolution

The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

of external relationships, based on a 2008 DNA and

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

analysis, shows the order as a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

, most closely related to endopterygote orders including the

Diptera Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

(true flies) and

Lepidoptera Lepidoptera ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

(butterflies and moths). Hymenoptera originated in the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

, with the oldest fossils belonging to the family

Xyelidae The Xyelidae are a comparatively species-poor family of sawflies comprising about 80 Extant taxon, extant species in five genera worldwide and is the only family in the superfamily Xyeloidea. The fossil record of the family is extensive, comprisi ...

. Social hymenopterans appeared during the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

. The evolution of this group has been intensively studied by

Alex Rasnitsyn Alexandr Pavlovich Rasnitsyn (Russian: Александр Павлович Расницын) is a Russian entomologist, expert in palaeoentomology, and Honored Scientist of the Russian Federation (2001). His scientific interests are centered on ...

, Michael S. Engel, and others. This clade has been studied by examining the mitochondrial DNA. Although this study was unable to resolve all the ambiguities in this clade, some relationships could be established. The

Aculeata Aculeata is a subclade of Hymenoptera containing ants, bees, and stinging wasps. The name is a reference to the defining feature of the group, which is the modification of the ovipositor into a stinger. However, many members of the group cannot ...

, Ichneumonomorpha, and

Proctotrupomorpha Proctotrupomorpha is a major subgrouping of the Apocrita within the Hymenoptera, containing mainly parasitic wasps. It contains the major groupings of Chalcidoidea, Diaprioidea, Proctotrupoidea, Cynipoidea and Platygastroidea The Hymenopte ...

were monophyletic. The

Megalyroidea Megalyroidea is a small hymenopteran superfamily of wasps that includes a single family, Megalyridae, with eight extant genera (plus around a dozen extinct ones) and 49 described species. Modern megalyrids are found primarily in the southern hem ...

and Trigonalyoidea are sister clades as are the

Chalcidoidea Chalcid wasps (, , for their metallic colour) are insects within the superfamily Chalcidoidea, part of the order Hymenoptera. The superfamily contains some 22,500 known species, and an estimated total diversity of more than 500,000 species, me ...

Diaprioidea Diaprioidea is a hymenopteran superfamily containing five extant families, though in the past these families were included in the superfamily Proctotrupoidea. References Parasitica Apocrita superfamilies {{Apocrita-stub ...

. The

Cynipoidea The Cynipoidea are a moderate-sized hymenopteran superfamily that presently includes five modern families and three extinct families, though others have been recognized in the past. The most familiar members of the group are phytophagous, especia ...

was generally recovered as the sister group to

and

which are each other's closest relations. The cladogram is based on Schulmeister 2003.

Anatomy

Hymenopterans range in size from very small to large insects, and usually have two pairs of wings. Their mouthparts are adapted for chewing, with well-developed

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

s (ectognathous mouthparts). Many species have further developed the mouthparts into a lengthy

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...

, with which they can drink liquids, such as

nectar Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists ...

. They have large

compound eyes A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distin ...

, and typically three simple eyes,

ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

. The forward margin of the hind wing bears a number of hooked bristles, or "

hamuli A hamus or hamulus is a structure functioning as, or in the form of, hooks or hooklets. Etymology The terms are directly from Latin, in which ''hamus'' means "hook". The plural is ''hami''. ''Hamulus'' is the diminutive – hooklet or little h ...

", which lock onto the fore wing, keeping them held together. The smaller species may have only two or three hamuli on each side, but the largest wasps may have a considerable number, keeping the wings gripped together especially tightly. Hymenopteran wings have relatively few veins compared with many other insects, especially in the smaller species. In the more ancestral hymenopterans, the

is blade-like, and has evolved for slicing plant tissues. In the majority, however, it is modified for piercing, and, in some cases, is several times the length of the body. In some species, the ovipositor has become modified as a

stinger A stinger (or sting) is a sharp organ found in various animals (typically insects and other arthropods) capable of injecting venom, usually by piercing the epidermis of another animal. An insect sting is complicated by its introduction of v ...

, and the

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

are laid from the base of the structure, rather than from the tip, which is used only to inject

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

. The sting is typically used to immobilise prey, but in some wasps and bees may be used in defense. Hymenopteran larvae typically have a distinct head region, three thoracic segments, and usually nine or 10 abdominal segments. In the suborder

Symphyta Sawflies are the insects of the suborder Symphyta within the order Hymenoptera, alongside ants, bees, and wasps. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plants where they lay ...

, the larvae resemble

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...

s in appearance, and like them, typically feed on leaves. They have large chewing mandibles, three pairs of thoracic limbs, and, in most cases, six or eight abdominal

proleg A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on other larval insects such as sawflies and a few other types of in ...

s. Unlike caterpillars, however, the prolegs have no grasping spines, and the antennae are reduced to mere stubs. Symphytan larvae that are wood borers or stem borers have no abdominal legs and the thoracic legs are smaller than those of non-borers. With rare exceptions, larvae of the suborder

Apocrita Apocrita is a suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Symphyta by the narrow "waist" ( petiole) formed ...

have no legs and are

maggot A maggot is the larva of a fly (order Diptera); it is applied in particular to the larvae of Brachycera flies, such as houseflies, cheese flies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and crane flies. ...

like in form, and are adapted to life in a protected environment. This may be the body of a host organism, or a cell in a nest, where the adults will care for the larva. In parasitic forms, the head is often greatly reduced and partially withdrawn into the prothorax (anterior part of the thorax). Sense organs appear to be poorly developed, with no ocelli, very small or absent antennae, and toothlike, sicklelike, or spinelike mandibles. They are also unable to defecate until they reach adulthood due to having an incomplete digestive tract (a blind sac), presumably to avoid contaminating their environment. The larvae of stinging forms (

) generally have 10 pairs of spiracles, or breathing pores, whereas parasitic forms usually have nine pairs present.

Reproduction

Sex determination

Among most or all hymenopterans, sex is determined by the number of

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

s an individual possesses. Fertilized eggs get two sets of chromosomes (one from each parent's respective

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

s) and develop into

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

females, while unfertilized eggs only contain one set (from the mother) and develop into

haploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

males. The act of fertilization is under the voluntary control of the egg-laying female, giving her control of the sex of her offspring. This phenomenon is called

haplodiploidy Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky. Haplodiploidy determines the sex ...

. However, the actual genetic mechanisms of haplodiploid sex determination may be more complex than simple chromosome number. In many Hymenoptera, sex is actually determined by a single gene locus with many alleles. In these species, haploids are male and diploids heterozygous at the sex locus are female, but occasionally a diploid will be homozygous at the sex locus and develop as a male, instead. This is especially likely to occur in an individual whose parents were

siblings A sibling is a relative that shares at least one parent with the subject. A male sibling is a brother and a female sibling is a sister. A person with no siblings is an only child. While some circumstances can cause siblings to be raised separat ...

or other close relatives. Diploid males are known to be produced by inbreeding in many ant, bee, and wasp species. Diploid biparental males are usually sterile but a few species that have fertile diploid males are known. One consequence of haplodiploidy is that females on average actually have more genes in common with their sisters than they do with their own daughters. Because of this, cooperation among kindred females may be unusually advantageous, and has been hypothesized to contribute to the multiple origins of

eusociality Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping genera ...

within this order. In many colonies of bees, ants, and wasps, worker females will remove eggs laid by other workers due to increased relatedness to direct siblings, a phenomenon known as

worker policing Worker policing is a behavior seen in colonies of social hymenopterans (ants, bees, and wasps) whereby worker females eat or remove eggs that have been laid by other workers rather than those laid by a queen. Worker policing ensures that the ...

. Another consequence is that hymenopterans may be more resistant to the deleterious effects of

inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and o ...

. As males are haploid, any recessive genes will automatically be expressed, exposing them to natural selection. Thus, the

genetic load Genetic load is the difference between the fitness of an average genotype in a population and the fitness of some reference genotype, which may be either the best present in a population, or may be the theoretically optimal genotype. The average i ...

of deleterious genes is purged relatively quickly.

Thelytoky

Some hymenopterans take advantage of

parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...

, the creation of

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s without

fertilization Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

Thelytoky Thelytoky (from the Greek ''thēlys'' "female" and ''tokos'' "birth") is a type of parthenogenesis in which females are produced from unfertilized eggs, as for example in aphids. Thelytokous parthenogenesis is rare among animals and reported in a ...

is a particular form of parthenogenesis in which female embryos are created (without fertilisation). The form of thelytoky in hymenopterans is a kind of automixis in which two haploid products (proto-eggs) from the same

meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...

fuse to form a diploid zygote. This process tends to maintain

heterozygosity Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mo ...

in the passage of the genome from mother to daughter. It is found in several ant species including the desert ant ''

Cataglyphis cursor ''Cataglyphis cursor'' is a species of ant in the genus ''Cataglyphis''. Described in 1846, it is known only from the Mediterranean parts of France. Reproduction Parthenogenesis is a natural form of reproduction in which growth and development ...

'', the clonal raider ant ''

Cerapachys biroi ''Ooceraea biroi'', the clonal raider ant, is a queenless clonal ant in the genus ''Ooceraea'' (recently transferred from the genus ''Cerapachys''). Native to the Asian mainland, this species has become invasive on tropical and subtropical islan ...

'', the predaceous ant ''

Platythyrea punctata ''Platythyrea punctata'' is a species of ant in the family Formicidae. References Further reading * Ponerinae Articles created by Qbugbot Insects described in 1858 {{ponerinae-stub ...

'', and the electric ant (little fire ant) ''

Wasmannia auropunctata The little fire ant (''Wasmannia auropunctata''), also known as the electric ant, is a small (approx long), light to golden brown (ginger) social ant native to Central and South America, now spread to parts of Africa (including Gabon and Camer ...

''. It also occurs in the Cape honey bee ''

Apis mellifera capensis The Cape honey bee or Cape bee (''Apis mellifera capensis'') is a southern South African subspecies of the western honey bee. They play a major role in South African agriculture and the economy of the Western Cape by pollinating crops and produc ...

''.

Oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ...

s that undergo automixis with central fusion often have a reduced rate of crossover recombination, which helps to maintain

and avoid

inbreeding depression Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. In ...

. Species that display central fusion with reduced recombination include the ants ''

'' and ''

'' and the Cape honey bee ''Apis mellifera capensis''. In ''A. m. capensis'', the recombination rate during meiosis is reduced more than tenfold. In ''W. auropunctata'' the reduction is 45 fold. Single queen colonies of the narrow headed ant ''

Formica exsecta ''Formica exsecta'' (the narrow-headed ant or excised wood ant) is a species of ant found from Western Europe to Asia. A rare formicine ant with a deeply excised head, ''F. exsecta'' forms small mounds up to around a foot in height consisting ...

'' illustrate the possible deleterious effects of increased homozygosity. Colonies of this species which have more homozygous queens will age more rapidly, resulting in reduced colony survival.

Diet

Different species of Hymenoptera show a wide range of feeding habits. The most primitive forms are typically phytophagous, feeding on flowers, pollen, foliage, or stems. Stinging wasps are predators, and will provision their larvae with immobilised prey, while bees feed on nectar and

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...

. A huge number of species are

parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...

s as larvae. The adults inject the eggs into a host, which they begin to consume after hatching. For example, the eggs of the endangered ''

Papilio homerus ''Papilio homerus'', commonly known as the Homerus swallowtail or Jamaican swallowtail, is the largest butterfly species in the Western Hemisphere. The species is endangered and faces a potentially bleak future. Only two small populations of the ...

'' are parasitized at a rate of 77%, mainly by Hymenoptera species. Some species are even

hyperparasitoid A hyperparasite, also known as a metaparasite, is a parasite whose host, often an insect, is also a parasite, often specifically a parasitoid. Hyperparasites are found mainly among the wasp-waisted Apocrita within the Hymenoptera, and in two ...

, with the host itself being another parasitoid insect. Habits intermediate between those of the herbivorous and parasitoid forms are shown in some hymenopterans, which inhabit the galls or nests of other insects, stealing their food, and eventually killing and eating the occupant.

Classification

Large rose sawfly (Arge pagana stephensii)

The Hymenoptera are divided into two groups; the

which have no waist, and the

which have a narrow waist.

Symphyta

The suborder

includes the

horntail Horntail or wood wasp are any of the 150 non-social species of the hymenopteran family Siricidae, a type of wood-eating sawfly. The common name "horntail" derives from the stout, spine-like structure at the end of the adult's abdomen, which is u ...

s, and parasitic wood wasps. The group may be

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, as it has been suggested that the family

Orussidae The Orussidae or the parasitic wood wasps represent a small family of sawflies (" Symphyta"). Currently, about 93 extant and four fossil species are known. They take a key position in phylogenetic analyses of Hymenoptera, because they form the s ...

may be the group from which the

arose. They have an unconstricted junction between the thorax and abdomen. The larvae are herbivorous, free-living, and

eruciform Eruciform (literally: "caterpillar-shaped") is the entomological term describing a certain class of shapes of insect larvae. Origin and application The word ''eruciform'' literally means "caterpillar-shaped" (from Latin "eruca", a caterpilla ...

, with three pairs of true legs,

s (on every segment, unlike

) and

. The prolegs do not have crochet hooks at the ends unlike the larvae of the Lepidoptera.

Apocrita

The

s, bees, and

s together make up the suborder (and clade)

, characterized by a constriction between the first and second abdominal segments called a wasp-waist ( petiole), also involving the fusion of the first abdominal segment to the

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

. Also, the larvae of all Apocrita lack legs, prolegs, or ocelli. The hindgut of the larvae also remains closed during development, with feces being stored inside the body, with the exception of some bee larvae where the larval anus has reappeared through developmental reversion. In general, the anus only opens at the completion of larval growth.

Threats

Hymenoptera as a group are highly susceptible to habitat loss, which can lead to substantial decreases in species richness and have major ecological implications due to their pivotal role as plant pollinators.