The second book is in nine propositions, eight of which deal with segments of spheres and include the problems of cutting a given sphere by a plane so that (a) the surfaces, (b) the volumes, of the segments are in a given ratio (Props.
The newly hatched insect closely resembles the parent, and the wing-rudiments appear externally on the second and third thoracic segments; but before the final moult the nymph remains quiescent, taking no food.
Most remarkable in this order is the structure of the feet; there are never more than two tarsal segments, and the claws, usually so conspicuous in insect feet, are reduced (fig.
Ten segments are recognizable in the abdomen, which is elongated and tapers at the hinder end.
There are two families of Terebrantia: (a) the Aeolpthripidae, whose feelers have nine segments; whose wings, relatively broad and rounded at the tip, have a few cross nervules, and whose ovipositor is curved backwards; and (b) the Thripidae, whose feelers have six to eight segments, whose narrow acuminate wings have no cross nervules, and whose ovipositor (fig.
As many as 162 segments in eight groups are practically used.
Should the rotating arms fail to pass over these correcting segments at their synchronous positions, correcting currents pass to a relay which cuts off momentarily the current actuating the tuning-fork, thereby altering the rate of vibration of the latter until the arms once more run together uniformly.
There are four transmitters and four receivers, which are operated independently by means of an adaptation of the multiplex system of working, and each circuit is provided with a number of segments set apart for its own use.
0, Optical section of two adjacent leptoids (sieve-tube segments) of Pteridophyte, with sieve plates (s.
Q, Three segments of a pitted vessel of Phanerogam.
It always consists of true parenchyma, and is entirely formed by the cutting off of segments from an apical cell.
In the Angiosperms there are always sistercells of sieve-tube segments and are called companion-cells (fig.
Where the leaves are crowded, a given leaf-gap is not closed before the next ones appear, and the solenostele thus becomes split up into a number of segments, sometimes band-shaped or semilunar, sometimes isodiametric in cross-section (fig.
Haplostele, the segments of inner endodermis, pericycle, phloem and ~ Pig.
I mesocycle joining with the corresponding outer segments to form a nearly concentric structure.
In the stem, segments are successively cut off from the sides of the tetrahedron, and b~ their subsequent division the body of the stem is produced.
In the root exactly the same thing occurs, but segments are cut off alsc from the base of the tetrahedron, and by the division of thes~ the root-cap is formed (fig.
Segments are then cut if from the outer sides of these initial cells.
The protoxylem and protophloem are developed a few cells from the inner and outer margins respectively of the desmogen strand, the desmogenic tissue left over giving rise to the segments of endocycle and pericycle capping the bundle.
For instance, the difference between the long-stalked and finely-cut leaves of Anemone attacked with rust and the normal leaves with broad segments, or between the urceolate leaves occasionally found on cabbages and the ordinary formin these cases undoubtedly pathological and teratological respectivelyis nothing like so great as between the upper and lower normalleaves of many Umhelliferae or the submerged and floating leaves of an aquatic Ranunculus or Cabomba.
The reduction is brought about simply by the segmentation of the spirem thread into half the number of segments instead of the normal number.
The segments of each ch~omosome are usually twisted upon.
In close contact with the segments of the sieve tubes are companion cells which communicate with the sieve tubes by delicate protoplasmic strands; they can be distinguished from ordinary pareochymatous cells by their small size and dense protoplasm.
Cambricum (originally found in Wales) has the pinnae themselves deeply cut into narrow segments; var.
2 b, 9b and 26 b, c); the number of segments is usually eleven, but may vary from two to more than twenty.
The articular surfaces of the haunches (coxae) of the fore-legs are often conical or globular, so that each limb works in a ball-and-socket joint, while the hind haunches are large, displacing the ventral sclerites of the first two abdominal segments (fig.
1, A) are of the usual insectan type, but in many families one, two, or even three of the five foot-segments may be reduced or absent.
From this point backwards the successive abdominal segments, as far as the seventh or eighth, can be readily made out.
The ninth and tenth segments are at most times retracted within the eighth.
The head - carrying feelers, mandibles and two pairs of maxillae - is succeeded by the three thoracic segments, each bearing a pair of strong five-segmented legs, whose feet, like those of the adult, carry two claws.
Ten segments can be distinguished in the tapering abdomen, the ninth frequently bearing a pair of tail-feelers (cerci), and the tenth, attached ventrally to the ninth, having the anal opening at its extremity and performing the function of a posterior limb, supporting and temporarily fixing the tail end of the insect on the surface over which it crawls.
In a large number of beetles of different families, stridulating areas occur on various segments of the abdomen, and are scraped by the elytra.
Such obvious features as the number of segments in the foot and the shape of the feeler were used by the early entomologists for distinguishing the great groups of beetles.
The arrangement dependent on the number of tarsal segments - the order being divided into tribes Pentamera, Tetramera, Heteromera and Trimera - was suggested by E.
Sharp (1899), who divides the order into six great series of families: Lamellicornia (including the chafers and stag-beetles and their allies with five-segmented feet and plate-like terminal segments to the feelers); Adephaga (carnivorous, terrestrial and aquatic beetles, all with five foot-segments); Polymorpha (including a heterogeneous assembly of families that cannot be fitted into any of the other groups); Heteromera (beetles with the fore and intermediate feet five-segmented, and the hind-feet four-segmented); Phytophaga (including the leaf-beetles, and longhorns, distinguished by the apparently four-segmented feet), and Rhynchophora (the weevils and their allies, with head prolonged into a snout, and feet with four segments).
Ganglbauer (1892) divides the whole order into two sub-orders only, the Caraboidea (the Adephaga of Sharp and the older writers) and the Cantharidoidea (including all other beetles), since the larvae of Caraboidea have five-segmented, two-clawed legs, while those of all other beetles have legs with four segments and a single claw.
- This tribe includes beetles of carnivorous habit with five segments on every foot, simple thread-like feelers with none of the segments enlarged to form club or pectination, and the outer lobs (galea) of the first maxilla usually two-segmented and palpiform (fig.
2) are Adephaga highly specialized for life in the water, the hind-legs having the segments short, broad and fringed, so as to be well adapted for swimming, and the feet without claws.
The fore-legs of many male dyticids have the three proximal foot-segments broad and saucer-shaped, and covered with suckers, by means of which they secure a firm hold of their mates.
Mandibles being well adapted for the capture of small insect-victims. The larvae are more specialized than those of other Adephaga, the head and prothorax being very large and broad, the succeeding segments slender and incompletely chitinized.
The number of antennal segments varies from eleven to two.
9, c) is slender with elongate legs, and the abdominal segments carry paired tracheal gills.
There are four malpighian tubes, and all five tarsal segments are usually recognizable.
With very few exceptions, the larva in this group is active and campodeiform, with cerci and elongate legs as in the Adephaga, but the leg has only four segments and one claw.
The Staphylinidae, or rove-beetles--a large family of nearly Io,000 species - may be known by their very short elytra, which cover only two of the abdominal segments, leaving the elongate hind-body with seven or eight exposed, firm terga (figs.
These segments are very mobile, and as the rove-beetles run along they often curl the abdomen upwards and forwards like the tail of a scorpion.
This is a somewhat heterogeneous group, most of whose members are characterized by clubbed feelers and simple, unbroadened tarsal segments - usually five on each foot - but in some familie andenera the males have less than the normal number on the feet of one pair.
The bestknown family is the Hydrophilidae, in which the feelers are short with less than eleven segments and the maxillary palpi very long.
Side, being scooped in bubbles by the terminal segments of the feelers when the insect rises to the surface.
- This tribe is distinguished by the presence of the normal five segments in the feet of the fore and intermediate legs, while only four segments are visible in the hind-foot.