Science / Spiders Glossary

Abdomen: The posterior division of the spider body, comprising the pedicel and usually largely unsegmented saclike portion bearing the spinnerets.

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) and sin(gamma) is called amplitude contrast ratio. It is different for different atoms, a . . . View Full Definition

Amplitude Correction: correction of the 3D Fourier amplitudes of the EM density map after angular refinement. This correction can be based on an analytical formula, namely by application of a temperature factor w . . . View Full Definition

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 object with arbitrary symmetry [van Heel, 1987a]. The method works on the basis of comparing s . . . View Full Definition

Annulations: Rings of pigmentation around leg segments.

Antennae: The segmented sensory organs often termed 'feelers,' borne on the heads of insects, crustacea, et cetera , but missing in all arachnids.

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 scorpions, mites, spiders, harvestmen, etc.

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 centipedes, millipedes, insects, crustaceans, spiders, scorpions, and many other less wel . . . View Full Definition

Astigmatism(Axial): an electron-optical lens aberration that causes the defocus to be a function of azimuth, and the contrast transfer function to deviate from circular symmetry about the optical axis. As a con . . . View Full Definition

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 peak is always in the origin, a shift position where both signal and noise contents of the . . . View Full Definition

Autophagy: The eating of an appendage shed from the body by autotomy or otherwise.

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