Abdomen: The posterior division of the spider body, comprising the pedicel and usually largely unsegmented sa
Accessory Claws: Serrated, thickened hairs near the true claws in some spiders.
Amplitude Contrast Ratio: For a weak phase, weak amplitude object, the ratio Qo between the contrast transferred by cos(gamma)
Amplitude Correction: correction of the 3D Fourier amplitudes of the EM density map after angular refinement. This correct
Anal Tubercle: The small caudal tubercle bearing the anal opening: the postabdomen.
Angular Reconstitution: a common-lines method designed to determine the relative angles between three projections of an obje
Annulations: Rings of pigmentation around leg segments.
Antennae: The segmented sensory organs often termed 'feelers,' borne on the heads of insects, crustacea, et ce
Anterior: Nearer the front or head end.
Appendages: Parts or organs (such as legs, spinnerets, chelicerae) that are attached to the body.
Arachnida: A principal division, or Class, of the air-breathing arthropods, the arachnids, including the scorpi
Arachnologist: One who studies the arachnids.
Araneae: The ordinal name of all spiders: same as Araneida.
Araneology: The branch of zoology that treats only of the spiders. Arthropod.The jointed-legged animals, such as
Astigmatism(Axial): an electron-optical lens aberration that causes the defocus to be a function of azimuth, and the con
Attachment Disc: The series of tiny lines that serve to anchor the draglines of spiders.
Autocorrelation Function (ACF): the cross-correlation function of an image with itself. The ACF is centrosymmetric, and its highest
Autophagy: The eating of an appendage shed from the body by autotomy or otherwise.
Autospasy: The loss of appendages by breaking them at a predetermined locus of weakness when pulled by an outsi
Autotomy: The act of reflex self-mutilation by dropping appendages: unknown in the arachnids.
Back-Projection: a method of 3D reconstruction from 2D projections. It is based on superposing 3D functions ('back-pr
Ballooning: Aeronautical dispersal by means of air currents acting on strands of silk.
Book Lungs: The respiratory pouches of the arachnids, filled with closely packed sheets or folds to provide maxi
Branchial Operculum: A sclerotized, hairless plate overlying the book lung.
Calamistrum: The more -or less extensive row of curved hairs on the hind metatarsi, used to comb the silk from th
Carapace: The exoskeletal covering, or shell, over the dorsal (upper) surface of the cephalothorax.
Cardiac Mark: An elongate midline mark on the anterior, dorsal surface of the abdomen which overlies the heart.
Catalepsy: The action of feigning death: induced by disturbance.
Cephalothorax: The anterior (front) of the two major divisions of the body of a spider.
Chelicerae: The pincerlike first pair of appendages of the arachnids: in spiders two-segmented, the distal porti
Chitin: A linear homopolysaceharide found as the characteristic molecule in the cuticle of arthropods. The m
Chorion: The outer covering or shell of the spider or insect egg.
Classification: separation of an image set into subsets according to the similarity of features [Frank, 1990]. Autom
Claw Tuft: A bunch of hairs at the tip of the leg tarsus in spiders with only two claws.
Claw Tufts: The pair of tufts of adhesive hairs present below the paired claws at the tip of the tarsi of many s
Clypeus: The area between the anterior row of eyes and the anterior edge of the carapace.
Coherence (Spatial): the degree to which separate parts of the electron wave have defined phase relationships, and are ab
Colulus: The slender or pointed appendage immediately in front of the spinnerets of some spiders: in other gr
Common Lines Method: a method of relating different projections of the same object to one another. In Fourier space, 2D p
Conductor: A semi-membranous structure in the male palp which supports and guides the embolus in insemination.
Condyle: A smooth, rounded protuberance sometimes present on the outer side of the chelicera, near its base.
Contrast Transfer Function (CTF): function that describes the transfer of information from the object (i.e., the object's projection)
Convolution Product: a 2D or 3D function obtained as the result of a superposition integral. The integrand is an image or
Correspondence Analysis (CA): a multivariate statistical analysis technique, used to analyze patterns of variation in an image dat
Coxa: The segment of leg nearest the body: modified in the palp to form the maxilla.
Coxal Glands: The excretory organs of arachnids, in spiders located opposite the coxae of the first and third legs
Cribellum: A sievelike, transverse plate, usually divided by a delicate keel into two equal parts, located in f
Cross-Correlation Function (CCF): a 2D or 3D function that is obtained by forming the scalar cross-product of two images or volumes(i.
Cuticle: The hard outer covering of an arthropod.
Cymbium: The broadened, hollowed-out tarsus of the male palp within which the palpal organs are attached.
Defocus: defocus setting (with reference to the Gaussian focus) in the electron microscope, normally given in
Defocus Spread: the spread of defocus due to the spread of electron energies or to the fluctuation of lens current.
Deutovum: The resting, spiderlike stage following the shedding of the chorion of the egg: the second egg.
Differential Phase Residual (DPR): a measure of statistical dependency between two averages, computed over rings in Fourier space as a
Distal: Pertaining to the outer end, furthest away from the body or point of attachment.
Dorsal: Pertaining to the upper surface.
Dorsum: In general, the upper surface.
Drift: a movement of the specimen during the exposure time, which causes a blurring of the image. It leaves
Ecdysis: Moulting: the periodic casting off of the cuticle.
Electron Energy: the energy of an electron accelerated from its rest energy by a voltage U is given by eU. For exampl
Embolus: The structure, in the male palp, containing the terminal part of the ejaculatory duct and its openin
Endite: The plate borne by the coxa of the pedipalps of most spiders, used to crush the prey: the maxilla.
Entelegyne: The group of spiders in which the females have an epigyne.
Epigastric Fold: A fold and groove separating the anterior part of the ventral abdomen (with epigyne and book lungs)
Epigyne: A more or less sclerotized and modified external structure associated with the reproductive openings
Epigynum: The more or less complicated apparatus for storing the spermatozoa, immediately in front of the open
Eulerian Angles: a set of three angles that define an orientation, or direction, in space. It goes back to the mathem
Exoskeleton: The hard, external, supportive covering found in all arthropods.
Exuviae: The parts of cuticle cast off during moulting.
Fang: The claw-like part of each chelicera: the poison duet opens near its tip.
Femur: The thigh: usually the stoutest segment of the spider's leg, articulated to the body through the tro
Folium: Any pattern of pigment on the dorsum of the abdomen which is fairly broad and leaf-shaped.
Fourier Ring Correlation (FRC): a measure of statistical dependency between two averages, computed by comparison of rings in Fourier
Fourier Shell Correlation (FSC): same as Fourier ring correlation, except that values of the discrete Fourier transforms are compared
Fourier Space: the argument space of the Fourier transform, spanned by the components of the spatial frequency vect
Fourier Transform (2D): mathematical representation of an image as a series of two-dimensional sine waves. The smaller the w
Fovea: A short median groove on the thoracic part of the carapace which marks the internal attachment of th
Gaussian Envelope Halfwidth: the halfwidth of the Gaussian in Fourier space, where the Gaussian is used to modify the envelope of
Genitalia: All the genital structures.
Gossamer: A light film of silk threads, or groups of these floating through the air.
Hackled Band: The composite threads of the cribellate spiders, spun by cribellum and combed by the calamistrum.
Haematodocha: A balloon of elastic connective tissue between groups of seletites in the male palp which distends w
Haplogyne: The group of spiders in which the females have no epigyne.
Head: The part of the carapace carrying the eyes which is separated from the thorax by a shallow groove.
High-Pass Filtration: multiplication of the Fourier transform of an image with a rotationally symmetric 2D function ('the
Labium: The lip, under the mouth opening and between the maxillae, attached to the front of the sternum.
Lanceolate: Tapering to a point.
Lateral: Pertaining to the side.
Low-Pass Filtration: multiplication of the Fourier transform of an image with a 2D function ('the filter') that attenuate
Lyriform Organ: A sensory organ near the distal end of limb segments formed of a group of parallel slit organs.
Maxilla: The mouthparts on each side of the labium which are the modified coxae of the palps..
Median: In the midline or middle.
Median Apophysis: A selerite arising from the middle division of the male palpal organs.
Metatarsus: (p1. metatarsi: adj. metatarsal) The sixth segment of the leg, counting from the body.
Orb Web: A two-dimensional web, roughly circular in design (and, strictly speaking, a misnomer). Silk threads
Padding: an operation that puts the given image into a larger-sized array, surrounding it with pixels equal t
Palp: Short for pedipalp. The appendage arising just in front of the legs, the coxa of which also forms th
Palpal Organs: The more or less complex structures fs)und in the terminal part of the adult male palp. They compris
Paracymbium: A structure in the male palp branching from, or loosely attached to, the cymbium.
Patella: (pl. Patellae, (adj. patellar) The fourth segment of the leg or palp, counting from the body.
Pedicel: The narrow stalk connecting the cephalothorax and the abdomen.
Pheromone: A chemical secreted by an animal in minute amounts which brings about a behavioral response in anoth
Phylogenetic: Pertaining to evolutionary relationships between and within groups.
Pixel Size: the number of Angstroms per pixel in the digitized micrograph. Pixel size is computed as ps (A/p) =
Point-Spread Function: the kernel in the superposition integral (convolution product) that expresses the effect of a linear
Posterior: Near the rear end.
Power Spectrum: intensity [= squared amplitude] of the Fourier transform, presented either in the form of an image (
Process: A projection from the main structure.
Procurved: Curved as an arc having its ends ahead of its center.
Prolateral: Projecting from, or on, the side facing forwards.
Proximal: Pertaining to the inner end: closest to the body or point of attachment.
Punctate: Covered with tiny depressions.
Random-Conical Reconstruction: a method of data collection and reconstruction used for single particles, typically used initially i
Recurved: Curved as an arc having its ends behind its center.
Refinement: generally, an iterative way of improving the accuracy, or resolution of a map by making use of const
Resolution: the extent of meaningful information in Fourier space, given by a spatial frequency radius. In 2D av
Reticulated: Like network.
Retrolateral: Projecting from, or on, the side facing backwards.
Rugose: Rough, wrinkled.
Scape: A finger-, tongue-, or lip-like projection from the midline of the female epigyne.
Sclerite: Any separate sclerotized structure connected to other structures by membranes.
Sclerotized: Hardened or horny: not flexible or membranous.
Scopula: (pl. scopulae) A brush of hairs on the underside of the tarsus and metatarsus in some spiders.
Scutum: A hard, often shiny, sclerotized plate on the abdomen of some spiders.
Septum: A partition separating two cavities or parts.
Sexual Dimorphism: A difference in form, color, size, etc., between sexes of the same species.
Sigillum: (pl. sigilla) An impressed, sclerotized spot, often reddish-brown. Often present on the dorsal surfa
Signal-To-Noise Ratio: ratio of signal variance to noise variance, computed for a given band limit.
Slit Organ: A stress receptor in the exoskeleton
Source Size: the size of the virtual electron source in the electron microscope, resulting in illumination diverg
Spatial Frequency: (a) a vector giving the frequency components (number of cycles per unit length, kx and ky ) of a gen
Spectral Signal-To-Noise Ratio (SSNR): measure of resolution proposed by Michael Unser and coworkers [Unser et al., 1987] [119-121].
Sperm Induction: The process of transferring the spermatozoa from the genital orifice beneath the base of the abdomen
Sperm Web: A web of few or many threads on which male spiders deposit the semen preparatory to taking it into t
Spermathecae: The vessels or receptacles in the epigyna of female spiders that store the spermatozoa of the males.
Spermatozoa: The mature sperm cells.
Spherical Aberration (3rd Order): electron optical lens aberration resulting in decreased focal length for rays that are farther from
Spiderling: A tiny, immature spider, usually the form just emerged from the egg sac.
Spiderling: The nymphal or immature spider, generally resembling the adult, hut smaller: fully mobile and no lon
Spine: A thick, stiff hair or bristle.
Spinnerets: The fingerlike abdominal appendages of spiders through which the silk is spun.
Spinners: Paired appendages at the rear end of the abdomen, below the anal tubercle, from the spigots of which
Spiracle: The opening of the tracheae on the underside of the abdomen.
Stadium: The interval between the molts of arthropods: instar: a period in the development of an arthropod.
Sternum: The heart-shaped or oval exoskeletal shield covering the under surface of the cephalothorax.
Stridulating Organ: A file-and-scraper for sound production: may be variously located on chelicerae, palps, legs, abdome
Subadult: Almost adult: the last instar before maturity.
Synonym: Each of two or more scientific names of the same rank used to denote the same taxon. The senior syno
Tarsus: The foot: the most distal segment of the legs, which bears the claws at its tip.
Taxon: Any taxonomic unit (eg. family, genus, species).
Taxonomy: The theory and practice of classifying organisms, part of systematics, the study of the kinds and di
Tergites: Dorsal sclerites on the body: the hard plates on the abdomen of the atypical tarantulas that indicat
Thon Rings: rings visible in the power spectrum of micrographs obtained by bright-field electron microscopy. The
Thorax: The second region of the body of insects that bears the legs: in spiders, fused with the head to for
Three-Dimensional Projection Matching: a method of refinement in reconstructing single particles from their projections [Penczek et al., 19
Tibia: (pl. Tibiae adj. tibial) The fifth segment of the leg or palp counting from the body.
Tracheae: The air tubes in insects: in spiders, tubular respiratory organs of different origin: by many though
Trichobothrium: (pl. trichobothria) A long, fine hair rising almost vertically from a socket on the leg. Trichobothr
Trochanter: The second segment of the leg or palp, counting from the body.
Ventral: Pertaining to the underside.
Wiener Filtration: application of the Wiener filter, designed to restore a signal in the presence of noise in an optima
Zygote: The fertilized egg.