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Kikiki huna female, on slide (cleared, except Fig. 23). 23 habitus, dorsal 24 head + right antenna, anterior 25 head, posterior 26 mesosoma, dorsal + metasoma, dorsal but focus at lower plane to show ovipositor. Scale line = 100 μm.
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A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera: Mymaridae) gen. n. and sp. n., is described from Costa Rica. It is compared with the related genus Kikiki Huber and Beardsley from the Hawaiian Islands, Costa Rica and Trinidad. A specimen of Kikiki huna Huber measured 158 μm long, thus holding the record for the smallest winged in...
Citations
... Most studies on insect flight focus on macroscopic insects with membraned wings, such as flies, moths and dragonflies [6][7][8][9][10][11]. However, there is a myriad of miniature flying insects with body size less than 1 mm [12,13]; some as small as a few hundred micrometres, e.g. a species of fairyflies called Tinkerbella nana [14]. In contrast to macroscopic insects, the morphology, behaviour and flight of miniature insects and the fluid-structure interactions (FSIs) of their wings are much less well understood, despite having long fascinated scientists [15][16][17]. ...
... These wings are collectively called bristled wings. Studies of a wide range of miniature insects [14,[21][22][23][24][25][26] provide detailed data on the number, shape and micro-structure of the bristles, as well as the dimensions of the central wing pads. In addition, the flight characteristics of several species of bristled-winged insects have been quantified by high-speed videos, allowing for analysis and numerical simulations of flight kinematics and aerodynamics at extremely small size scales [26,27,[29][30][31][32]. ...
... (b) Number of bristles n plotted against the ratio l/B in insects, where l is the average bristle length. Measurements gathered or estimated from [14,[21][22][23][24][25][26][27][28] are tabulated in tables S1 and S2 in the electronic supplementary material. ...
The smallest flying insects often have bristled wings resembling feathers or combs. We combined experiments and three-dimensional numerical simulations to investigate the trade-off between wing weight and drag generation. In experiments of bristled strips, a reduced physical model of the bristled wing, we found that the elasto-viscous number indicates when reconfiguration occurs in the bristles. Analysis of existing biological data suggested that bristled wings of miniature insects lie below the reconfiguration threshold, thus avoiding drag reduction. Numerical simulations of bristled strips showed that there exist optimal numbers of bristles that maximize the weighted drag when the additional volume due to the bristles is taken into account. We found a scaling relationship between the rescaled optimal numbers and the dimensionless bristle length. This result agrees qualitatively with and provides an upper bound for the bristled wing morphological data analysed in this study.
... Most studies on insect flight focus on macroscopic insects with membraned wings, such as flies, moths, and dragonflies [6][7][8][9][10][11]. However, there is a myriad of miniature flying insects with body size less than 1 mm [12,13]; some as small as a few hundred microns, e.g., a species of fairyflies called Tinkerbella nana [14]. In contrast to macroscopic insects, the morphology, behavior, and flight of miniature insects and the fluidstructure interactions (FSI) of their wings are much less well-understood, despite having long fascinated scientists [15][16][17]. ...
... These wings are collectively called bristled wings. Studies of a wide range of miniature insects [14,[19][20][21][22][23][24] provide detailed data on the number, shape, and micro-structure of the bristles, as well as the dimensions of the central wing pads. In addition, the flight characteristics of several species of bristled-winged insects have been quantified by high-speed videos, allowing for analysis and numerical simulations of flight kinematics and aerodynamics at extremely small size scales [24][25][26][27][28][29]. ...
... The Reynolds number (Re) of the bristled wing is usually estimated based on the wing chord length (Re c ) and has been reported to be Re c =O(1) − O (10) [16,32,34]. [14,[19][20][21][22][23][24][25]35] are tabulated in Tables S1 and S2 in the supplementary information. ...
The smallest flying insects often have bristled wings resembling feathers or combs. We combined experiments and three-dimensional numerical simulations to investigate the trade-off between wing weight and drag generation. In experiments of bristled strips, a reduced physical model of the bristled wing, we found that the elasto-viscous number indicates when reconfiguration occurs in the bristles. Analysis of existing biological data suggested that bristled wings of miniature insects lie below the reconfiguration threshold, thus avoiding drag reduction. Numerical simulations of bristled strips showed that there exist optimal numbers of bristles that maximize the weighted drag when the additional volume due to the bristles is taken into account. We found a scaling relationship between the rescaled optimal numbers and the dimensionless bristle length. This result agrees qualitatively with and provides an upper bound for the bristled wing morphological data analyzed in this study.
... Many of the smallest flying insects have bristled wings (Fig. 9), e.g. thrips (Lewis, 1973), tiny beetles (Polilov, 2005) and fairyflies (Huber and Noyes, 2013). ...
Approximately half of the existing winged-insect species are of very small size (wing length about 0.3-4 mm); they are referred to as miniature insects. Yet until recently, much of what we know about the mechanics of insect flight was derived from studies on relatively large insects, such as hoverflies, honey bees and hawkmoths. Because of their very small size, many miniature insects fly at a Reynolds number (Re) on the order of 10 or less. At such a low Re, the viscous effect of the air is very large: A miniature insect moves through the air as would a bumble bee move through mineral oil. Miniature insects must use new flapping mode and new aerodynamic mechanisms to fly. Over the past decade, much work has been done in the study of the mechanics of flight in miniature insects: novel flapping modes have been discovered and new mechanisms of aerodynamic force generation have been revealed; progress has also been made on the fluid-mechanics related flight problems, such as flight power requirements and flight dynamic stability. This article reviews these developments and discusses potential future directions.
... The number of ommatidia therefore determines the total number of images an eye can form, or its spatial information capacity. Ommatidia can be counted in micrographs, ranging from about 20 in the fairyfly Kikiki huna (body length = 158 µm) 21,22 to over 30,000 in large dragonflies 5 . Compound eyes further divide into two structural groups: apposition eyes, in which pigment cells between ommatidia restrict incoming light to a single rhabdom, such that lens size limits optical sensitivity (Fig. 1a), and superposition eyes, in which light travels through a clear zone that allows many facets to contribute to each point (Fig. 1b), thereby multiplying the final sensitivity. ...
With a great variety of shapes and sizes, compound eye morphologies give insight into visual ecology, development, and evolution, and inspire novel engineering. In contrast to our own camera-type eyes, compound eyes reveal their resolution, sensitivity, and field of view externally, provided they have spherical curvature and orthogonal ommatidia. Non-spherical compound eyes with skewed ommatidia require measuring internal structures, such as with MicroCT (µCT). Thus far, there is no efficient tool to characterize compound eye optics, from either 2D or 3D data, automatically. Here we present two open-source programs: (1) the ommatidia detecting algorithm (ODA), which measures ommatidia count and diameter in 2D images, and (2) a µCT pipeline (ODA-3D), which calculates anatomical acuity, sensitivity, and field of view across the eye by applying the ODA to 3D data. We validate these algorithms on images, images of replicas, and µCT eye scans from ants, fruit flies, moths, and a bee.
... morphological adaptations, some of which set records among the insects. For example, the smallest insect on Earth is a fairy wasp of the genus Dicopomorpha (Mymaridae) 19 , while the longest egg-laying organ (the ovipositor, measured in absolute size) occurs in Darwin wasps of the genus Megarhyssa (Ichneumonidae) 20 . These two extreme examples have a major life history strategy in common: they are both parasitoids, carnivores that complete their entire life cycle feeding on just one individual prey item, the host 21 . ...
... The first transition between phytophagy and parasitoidism is estimated in the Late Triassic in the most recent common ancestor (MRCA) of Vespina (node 6, Fig. 2; Supplementary Figs. [18][19]. Parasitoidism thus evolved once and remained the dominant life strategy in Hymenoptera, with no subsequent major innovations in life history evolving until the Early Cretaceous around 140 Ma (Fig. 2). ...
The order Hymenoptera (wasps, ants, sawflies, and bees) represents one of the most diverse animal lineages, but whether specific key innovations have contributed to its diversification is still unknown. We assembled the largest time-calibrated phylogeny of Hymenoptera to date and investigated the origin and possible correlation of particular morphological and behavioral innovations with diversification in the order: the wasp waist of Apocrita; the stinger of Aculeata; parasitoidism, a specialized form of carnivory; and secondary phytophagy, a reversal to plant-feeding. Here, we show that parasitoidism has been the dominant strategy since the Late Triassic in Hymenoptera, but was not an immediate driver of diversification. Instead, transitions to secondary phytophagy (from parasitoidism) had a major influence on diversification rate in Hymenoptera. Support for the stinger and the wasp waist as key innovations remains equivocal, but these traits may have laid the anatomical and behavioral foundations for adaptations more directly associated with diversification.
... The transition within Symphyta from phytophagy mediated by symbiotic fungi in wood wasps to parasitoidism in the orussoid-apocritan lineage denotes a radical change facilitating the subsequent radiation of the order as parasitoids [9,10]. Parasitoidism in Hymenoptera arose about 200-250 Ma [1,3,4], [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] Ma after the origin of the order. It should be noted that Peters et al. [3] include Orussidae within a clade separate from the remaining Symphyta. ...
... Proctotrupomorpha appears to have arisen around 200 Ma, and several lineages within the clade are associated with extreme miniaturization, especially in the Mymarommatidae and the chalcidoid Mymaridae ('fairy flies') and Trichogrammatidae, with fully winged specimens approx. 0.14-mm long [37,38]. It is among the Chalcidoidea, and in particular the egg parasitoids and Sternorrhyncha parasitoids, where the most important biological control agents, for example, Anagyrus lopezi (Encyrtidae), have been selected [39]; see also Box 2. ...
Parasitoid wasps are the most successful group of insect parasitoids, comprising more than half the known diversity of Hymenoptera and probably most of the unknown diversity. This life-style has enabled them to be used as pest control agents conferring substantial economic benefits to global agriculture. Major lineages of parasitoid wasps include Ichneumonoidea, Ceraphronoidea, Proctotrupomorpha and a number of aculeate families. The parasitoid life-style arose only once among basal Hymenoptera, in the common ancestor of the Orussidae and Apocrita some 200+ Ma ago. The ancestral parasitoid wasp was probably an idiobiont on wood-living beetle larvae. From this comparatively simple biology, Hymenoptera radiated into an incredible diversity of hosts and parasitoid lifestyles, including hyperparasitoidism, kleptoparasitoidism, egg-parasitoidism and polyembryony, in several instances co-opting viruses to subdue their hosts. Many lineages evolved beyond the parasitoid niche, becoming secondarily herbivorous or predatory nest provisioners and eventually giving rise to most instances of insect societies.
... In recent years, the anatomy of the smallest insects (Polilov, 2016(Polilov, , 2017Minelli and Fusco, 2019) and collembolans (Tullbergiidae) (Panina et al., 2019) has been studied in detail, but the miniaturization of arachnids has been studied little, despite the fact that mites are presumably the smallest terrestrial arthropods (Huber and Noyes, 2013;Dunlop, 2019). ...
... Acariform four-legged mites (Acariformes, Eriophyoidea) of the family Eriophyidae are some of the smallest mites (Dunlop, 2019), they are microscopic parasites of plants, closely related to the group of soil mites Nematalycidae (Bolton et al., 2017;Klimov et al., 2018Klimov et al., , 2022. Due to parasitism, Eriophyoidea went the way of miniaturization (Nuzzaci and Alberti, 1996), reaching almost the minimum size possible for multicellulars of 80e90 mm (Huber and Noyes, 2013). ...
Miniaturization is one of the important trends in the evolution of terrestrial arthropods. In order to study adaptations to microscopic sizes, the anatomy of the smallest insects was previously studied, but not the anatomy of the smallest mites. Some of the smallest mites are Eriophyidae. In this study we describe for the first time the anatomy of the mite Achaetocoptes quercifolii, which is about 115 μm long. For this purpose, we used light, scanning, and transmission electron microscopy and performed 3D reconstructions. The anatomy of A. quercifolii is compared with the anatomy of larger representatives of Eriophyoidea. Despite the small size of the studied species, there is no considerable simplification of its anatomy compared to larger four-legged mites. A. quercifolii has a number of miniaturization effects similar to those found in microinsects: a strong increase in the relative volume of the reproductive system, an increase in the relative volume of the brain, reduction in the number and size of cells of the nervous system. As in some larger four-legged mites, A. quercifolii undergoes midgut lysis at the stage of egg production. On the other hand, in A. quercifolii a greater number of opisthosomal muscles are preserved than in larger gall-forming four-legged mites.
... With approximately 1 million described species, and perhaps 5 to 10 times more undescribed ones (García-Robledo et al., 2020;Stork, 2018), insects are the most diverse group of organisms on Earth. This unparalleled species richness is mirrored by the diversity of life strategies and morphological configurations, including the extreme variation in body size, ranging from 0.14 to over 550 mm (Chown & Gaston, 2010;Huber & Noyes, 2013). A miniaturized body, often requiring drastic changes in external morphology and internal anatomy (Minelli & Fusco, 2019), is usually an adaptation for environments with very limited space, for example insect eggs in the case of egg parasitoids (e.g., Huber & Noyes, 2013) or fungal hymenium tubes in some featherwing beetles (Grebennikov, 2008;Polilov, 2015a;Polilov et al., 2019). ...
... This unparalleled species richness is mirrored by the diversity of life strategies and morphological configurations, including the extreme variation in body size, ranging from 0.14 to over 550 mm (Chown & Gaston, 2010;Huber & Noyes, 2013). A miniaturized body, often requiring drastic changes in external morphology and internal anatomy (Minelli & Fusco, 2019), is usually an adaptation for environments with very limited space, for example insect eggs in the case of egg parasitoids (e.g., Huber & Noyes, 2013) or fungal hymenium tubes in some featherwing beetles (Grebennikov, 2008;Polilov, 2015a;Polilov et al., 2019). Yet even free-living insects can be extremely miniaturized, with body sizes notably below 1 mm. ...
Sphaeriusidae (Coleoptera: Myxophaga) is a group of shiny, blackish and hemispherical riparian beetles, known for their miniaturized bodies. They are worldwide in distribution , but very limited information is available about taxonomic and morphological diversity, and natural and evolutionary history. The aim of this study is to help fill in these gaps. We examined the external morphology of modern representatives using scanning electron microscopy (SEM), and reconstructed the phylogeny of the family using five DNA markers (cytochrome oxidase I, 18S rRNA, 28S rRNA, CAD and wingless). Our results suggest a larger morphological diversity than previously expected, corresponding to the deep genetic divergences of principal lineages. We also examined two inclusions in 99-million-year-old Burmese amber. The integration of all evidence allows us to recognize three genera: the extinct genus †Burmasporum Kirejtshuk, the newly defined genus Bezesporum gen.nov. preserved in Burmese amber (B. burmiticum sp.nov.) and present in the modern fauna of Southeast Asia, and the genus Sphaerius Waltl with a worldwide distribution. Sphaerius species are morphologically highly uniform, with the exception of species from Australia and South Africa, which share some characteristics with Bezesporum gen.nov. despite being resolved as deeply nested lineages of Sphaerius by DNA data. The presence of Bezesporum gen.nov. in Burmese amber and in recent fauna indicates that Sphaeriusidae largely maintained their specific morphology and specialized riparian lifestyle for at least 100 million years. Therefore, they can be considered an exceptionally conserved group, with a minimum of evolutionary changes over a long period. Our study also demonstrates that the species numbers and fine-scale morphological diversity of Sphaeriusidae are larger than expected in both the past and present-day faunas. Both were apparently underestimated due to the minute body size and cryptic habits of these beetles.
... The family Mymaridae, commonly known as fairyflies (Blackbourn 1935), includes the smallest members of the Chalcidoidea (Hymenoptera) (Annecke & Doutt 1961;Noyes & Valentine 1989;Lin et al. 2007;Huber et al. 2009;Huber & Noyes 2013). The name fairyflies refers to their usually slender bodies, very small size, and their delicate, fringed wings ). ...
... The name fairyflies refers to their usually slender bodies, very small size, and their delicate, fringed wings ). Some are less than 0.19 mm long, being the smallest of all winged insects (Noyes & Valentine 1989;Huber & Noyes 2013), while a few others occurring in the Southern Hemisphere may reach 6.0 mm in length, thus being considered giants of the world mymarids (Noyes & Valentine 1989;Gibson 1997;Huber & Noyes 2013;Pricop 2013;Huber 2017). Mymaridae are cosmopolitan, being an abundant group of Hymenoptera almost everywhere, particularly throughout the tropical and temperate regions (except Antarctica) (Annecke & Doutt 1961;Triapitsyn & Berezovskiy 2001). ...
... The name fairyflies refers to their usually slender bodies, very small size, and their delicate, fringed wings ). Some are less than 0.19 mm long, being the smallest of all winged insects (Noyes & Valentine 1989;Huber & Noyes 2013), while a few others occurring in the Southern Hemisphere may reach 6.0 mm in length, thus being considered giants of the world mymarids (Noyes & Valentine 1989;Gibson 1997;Huber & Noyes 2013;Pricop 2013;Huber 2017). Mymaridae are cosmopolitan, being an abundant group of Hymenoptera almost everywhere, particularly throughout the tropical and temperate regions (except Antarctica) (Annecke & Doutt 1961;Triapitsyn & Berezovskiy 2001). ...
A review of the known Mymaridae (Hymenoptera: Chalcidoidea) in Egypt is presented based on the available literature records and new collections made during 2015–2021. Twenty-two named species in 13 genera are known to occur in Egypt, of which three, Arescon Walker, Dicopus Enock, and Stephanodes Enock, are recorded for the first time from the country, each with a single species. Three species, Anagrus frequens Perkins, Camptoptera papaveris Foerster, and Erythmelus flavovarius (Walker), are also recorded here for the first time from Egypt. A new species, Arescon splendidus Gadallah, Edmardash & Abul-Sood, n. sp., is described and illustrated. The genus Polynema Haliday is excluded from the present study and will be treated separately when fresh specimens of the two species described previously from Egypt are collected from the respective type localities. An identification key based on females for all the Egyptian species of Mymaridae is provided.
... Bristled wing models and non-dimensional parameters. Figure 1a displays a schematic diagram of the bristled wing of a fairyfly, Tinkerbella nana (re-drawn from Ref. 3 ). During flight, the distal part of the wing, where the bristles are nearly parallel to the direction of the wing span, moves faster than the proximal part and generates most of the aerodynamic force. ...
... The aspect ratio (AR) of the wing is defined as the ratio of the wing span (the cylinder length L) to the chord length c. According to the micrographs of the real bristled wings in Ref. 3 , we considered AR = 1.5-2.5 as biologically relevant. To examine the 3-D effect caused by the finite span, we also constructed a 2-D bristled wing model, which is a chordwise transection of the 3-D model and has been widely used by previous researchers (e.g., Refs. ...
... From Fig. 11, we can also see that the flow velocities around the two cylinders closest to the leading edge (cylinders No. 1 and 2) are higher than those around the rest; and the flow fields around cylinders No. 3, 4, 5, and 8 are almost identical, implying that the flow around a cylinder in the bristled wing is affected mainly by www.nature.com/scientificreports/ the two cylinders above and the two cylinders below it. Therefore, the flow velocities around different cylinders in the inner chord (i.e., cylinders No. [3][4][5][6][7][8][9][10][11][12][13], are reduced to the same degree, resulting in the equally low drag coefficients of the cylinders. However, for the leading edge of the wing (see cylinder No. 1 in Fig. 11), there is no cylinder above. ...
The smallest insects fly with bristled wings at very low Reynolds numbers ( Re ) and use the drag of the wings to provide the weight-supporting force and thrust. Previous studies used two-dimensional (2-D) models to study the aerodynamic force and the detailed flow field of the bristled wings, neglecting the three-dimensional (3-D) effect caused by the finite span. At high Re , the 3-D effect is known to decrease the aerodynamic force on a body, compared with the 2-D case. However, the bristled wing operates at very low Re , for which the 3-D effect is unknown. Here, a 3-D model of the bristled wing is constructed to numerically investigate the detailed flow field and the aerodynamic force of the wing. Our findings are as follows: The 3-D effect at low Re increases the drag of the bristled wing compared with that of the corresponding 2-D wing, which is contrary to that of the high- Re case. The drag increase is limited to the tip region of the bristles and could be explained by the increase of the flow velocity around the tip region. The spanwise length of the drag-increasing region (measuring from the wing tip) is about 0.23 chord length and does not vary as the wing aspect ratio increases. The amount of the drag increment in the tip region does not vary as the wing aspect ratio increases either, leading to the decrease of the drag coefficient with increasing aspect ratio.
