Handbook of medical entomology . individ-uals who are made seriously sick by a single sting, regardless of thepoint of entr>. Some individuals scarcely notice a mosquito bite,others find it ven* painful, and so illustrations of this difference inindividuals might be multiplied. In considering the poisonous arthropods, we shall take them up bygroups. The reader who is unacquainted with the systematic rela-tionship of insects and their allies is referred to Chapter XII. Noattempt will be made to make the lists under the various headingsexhaustive, but typical forms wnll be discussed. ARANEIDA
Handbook of medical entomology . individ-uals who are made seriously sick by a single sting, regardless of thepoint of entr>. Some individuals scarcely notice a mosquito bite,others find it ven* painful, and so illustrations of this difference inindividuals might be multiplied. In considering the poisonous arthropods, we shall take them up bygroups. The reader who is unacquainted with the systematic rela-tionship of insects and their allies is referred to Chapter XII. Noattempt will be made to make the lists under the various headingsexhaustive, but typical forms wnll be discussed. ARANEIDA OR SPIDERS Of aU the arthropods there are none which are more tmiversalhfeared than are the spiders. It is commonly supposed that themajority, if not all the species are poisonous and that they are aggres-sive enemies of man and the higher animals, as weU as of lower forms. That they really secrete a poison ma> be readily inferred from theeffect of their bite upon insects and other small forms. Moreover, Araneida or Spiders. Head of a spider showingpoison gland (c) and its re-lation to the chelicera (a). the presence of definite and well-developed poison glands can easilybe shown. They occur as a pair of pouches (fig. i) lying within thecephalothorax and connected by a delicateduct with a pore on the claw of the chelicera,or so-called mandible on the convex surfaceof the claw in such a position that it is notplugged and closed by the flesh of the glands may be demonstrated by slowlyand carefully twisting off a chelicera andpushing aside the stumps of muscles at itsbase. By exercising care, the chitinous wallof the chelicera and its claw may be brokenaway and the duct traced from the gland to its outlet. The innerlining of the sac is constituted by a highly developed glandularepithelitmi, supported by a basement membrane of connectivetissue and covered by a musctdar layer, (fig. 2). The muscles, whichare striated, are spirally arranged (fig. i), and are doubtless
Size: 1664px × 1502px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectinsectp, bookyear1915
