Body segments

After some moments of darting and buzzing over an ant s head, an agile female fly swoops down and deposits a single egg in the ant s thorax (the second of its three major body segments, between its head and abdomen). Her assault requires only half a second, too fast to follow in detail, but it frequently knocks the ant... 

Annelida Segmented worms, leeches Body segmentation, complex organ systems marine, freshwater and terrestrial, some are parasites... 

The Mandibulata is by far the largest group of arthropods, since it contains the insects. Animals in this group have two or three body segments, one or two pairs of antennae, and one pair of mandibles. The subphylum Mandibulata is divided into six classes, the largest two of which are the Hexapoda (insects) and Crustacea (crustaceans). 

Insects are typified by three main body segments, which are themselves further segmented, antennae, mandibles, three pairs of legs, two pairs of wings, and compound eyes. There is incredible diversity in this huge group and body types and sizes vary greatly. 

The Crustacea is the second largest group within the Arthropods. This diverse group includes lobsters, crabs, shrimp, sow bugs, barnacles, and many other forms. Over 38,000 species of Crustacea are known and there are probably many more yet to be discovered. Most Crustacea have a hard chitinous exoskeleton, three body segments, two pairs of antennae, and gills for breathing. Most... 

Plant yellow and stunted, wilts during hot days and recovers at night. Causes Wire-worms bean leaf beetle larvae root knot nematodes. If you suspect any of these pests, pull up a plant and examine the roots. Wireworm larvae are up to 1 A", yellow to reddish brown, slender, tough-bodied, segmented grubs. Adults are A" long, dark-colored, elongated click beetles. Apply parasitic nematodes to the soil to control. 

Wireworms are I A" long, yellow to reddish brown, slender, tough-bodied, segmented larvae with brown heads. Adults are dark-colored, elongated click beetles. 

Fused Head Thorax Prosoma/Cephalothorax] Body Segments Opisthosoma) 5 Sting Telsori)... 

As we have just seen, the spatially controlled transcription of pair-rule genes sets up repeating units within the initial sheet of cells composing the early Drosophila embryo. Later, these repeating units must diversify only some of them will produce appendages, and they will specialize internally as well. This early diversification of body segments depends on the Hox genes, which are important switches that control cell identities and indeed the identities of whole parts of an animal. 

Three Drosophila segment-polarity genes, engrailed, wingless, and hedgehog, are expressed in one-cell-wide stripes in each of the 14 body-segment primordia. 

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