Entomology : with special reference to its biological and economic aspects . n account of thesecorrespondences and for otherweighty reasons it is believedthat arthropods have de-scended from annelid-like an-cestors. Annelids, however,as contrasted with arthropods,have segments that are essen-tially alike, have no externalskeleton and never havepaired limbs that are of Arthropoda.—Excepting the king-crab, tri-lobites and a few other aber-rant forms of uncertain posi-tion, the members of theseries, or phylum, Arthropodafall into six distinct classes,namely, Crustacea, Arach-nida,
Entomology : with special reference to its biological and economic aspects . n account of thesecorrespondences and for otherweighty reasons it is believedthat arthropods have de-scended from annelid-like an-cestors. Annelids, however,as contrasted with arthropods,have segments that are essen-tially alike, have no externalskeleton and never havepaired limbs that are of Arthropoda.—Excepting the king-crab, tri-lobites and a few other aber-rant forms of uncertain posi-tion, the members of theseries, or phylum, Arthropodafall into six distinct classes,namely, Crustacea, Arach-nida, Malacopoda, Diplopoda,Chilopoda and I n s e c t a .These classes are character-ized as follows: Crustacea.—Aquatic, as arule. Head and thorax often united into a paired appendages, typically biramous (Y-shaped) ;abdominal limbs often present. Two pairs of antennae. Res-piration branchial (by means of gills) or cutaneous (directlythrough the skin). The exoskeleton contains carbonate andphosphate of lime in addition to chitin. Example, A scorpion, Biithus. Natural size. CLASSIFICATION Arachnida.—Terrestrial. Usually two regions, cephalo-thorax and abdomen; though various Acarina ha\e but oneand Solpugida have all three-—head, thorax and unsegmented, bearing two pairs of oral append- FlG. 3.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
