2, looks as though composed of a number of segments, gradually decreasing in size from base to tip like the joints of a telescope, instead of tapering gradually and evenly from one extremity to the other.
The mandibles are normally five-jointed, with remnants of an outer branch on the second joint, the biting edge varying from strong development to evanescence, the terminal joints or " palp " giving the organ a leg-like appearance and function, which disappears in suctorial genera such as Paracytherois.
In September 1839 a 3-foot speculum was finished and mounted on an altazimuth stand similar to Herschel's; but, though the definition of the images was good (except that the diffraction at the joints of the speculum caused minute rays in the case of a very bright star), and its peculiar skeleton form allowed the speculum to follow atmospheric changes of temperature very quickly, Lord Rosse decided to cast a solid 3-foot speculum.
When blasting is resorted to, advantage is taken of the natural cuts or joints, as the rock is readily thrown or worked off these.
On the Hessian fly, Cecidomyia destructor, Say, the May brood of which produces swellings immediately above the joints of barley attacked by it, see Asa Fitch, The Hessian Fly (Albany, 1847), reprinted from Trans.