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Melitta guide updated

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  • Michael Orr
    Hello all, With the addition of the Western M. californica, this guide has been successfully expanded to include all species of the United States, while also
    Message 1 of 1 , May 9, 2011
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      Hello all,


      With the addition of the Western M. californica, this guide has been successfully expanded to include all species of the United States, while also receiving several additional characters in order to improve the guide. This effort was based upon both loans acquired from the AMNH and reference to Michez and Eardley's 2007 work on the group.

      The guide may be found here:
      http://www.discoverlife.org/mp/20q?guide=Melitta

      For convenience's sake, here are the guide's characters and their scorings:
      Females, head, length and shape of mandibles
      Mandible equal to or shorter than length of eye, distal half wide and flat with a single tooth before the tip, distal half not shaped like a knife blade (americana, californica, eickworti)
      Mandible longer than length of eye, distal half shaped as a pointed knife blade with two small teeth on inner margin (melittoides)

      Females, M. eickworti vs. M. americana
      M. americana - The very large pits of the scutum are spaced much more densely, such that many of these pits are touching each other even in the posterior half, although this density is usually lower posteromedially - In direct comparison, scutellum more densely pitted in the anterior half - Pits on T1 and T2 TOUCHING to nearly touching, separated by less than 1 pit diameter, this most obvious when comparing the basal half of T2 - Pygidial plate with the raised area appearing to resemble a triangle
      M. eickworti - The very shallow yet large pits of the scutum are spaced much more sparsely, such that almost no pits are touching each other and the overall pit spacing appearing to be highly irregular - In direct comparison, scutellum less densely pitted in the anterior half - Pits on T1 and T2 sparse, averaging well more than 1 pit diameter apart, this most obvious when comparing the basal half of T2 - Pygidial plate with raised area appearing irregular, with the base a strongly-convex bump and the apical portion being a raised line which extends towards the apex

      Males, abdomen, S6, shape of rim
      Apical rim broadly ROUNDED OUT, lacking a semi-circle shaped indent - If with any type of indent, then a very small v-shaped notch in the center comprising much less than 1/2 the rim (californica, melittoides)
      Apical rim with a semi-circle shaped indent across the middle 1/2 to 2/3 of the rim (americana, eickworti)

      Males, abdomen S6, pattern of hair
      Hair APPEARING as three distinct tufts, one apical and two lateral tufts, but the lateral tufts may appear nearly contiguous with the apical tuft along the rim (americana)
      Hair NOT arranged into three distinct tufts, although some apical hairs may be quite a bit longer than hair on the sides (eickworti)
      Hair arranged into THREE DISTINCT TUFTS, one apical and two lateral tufts, lateral tufts are NOT contiguous with the apical tuft along the rim (melittoides)

      Females, head, clypeus, pitting
      Pitting sparse and shallow lateral to the often-impunctate midline of the clypeus, sometimes hard to see and with an average pit spacing well over one pit diameter (melittoides)
      Pitting dense and distinct lateral to the often-impunctate midline of the clypeus, easily seen and with an average pit spacing of at most about one pit diameter (americana, californica, eickworti)

      Males, thorax, scutum, hair color
      With only light hairs (americana)
      With both light and black hairs, although the light hairs are dominant enough that the presence of black hairs may not be initially obvious, never equal in density to the light hairs (californica)
      With both light and black hairs, the black hairs dense enough that their presence is obvious, often equal in density to the light hairs (eickworti, melittoides)

      Males, M. americana vs M. eickworti, form of apical disc of S8
      M. americana - Apical disc with a distinct longitudinally-impressed line down the center, leaving the disc convex to either side - In direct comparison, larger, and with a much lower degree of black hairs on the face just interior to the inner edge of the eye and on the vertex
      M. eickworti - Apical disc appearing either flat or concave throughout its entirety, not divided down the middle by an impressed line - In direct comparison, smaller, and with a much higher degree of black hairs on the face just interior to the inner edge of the eye and on the vertex

      Females, head, vertex, hair color, ignoring the small amount of black hairs which may or may not be present
      Hair color white to slightly off-white (californica, melittoides)
      Hair color orangish to yellowish (americana, eickworti)

      Females, abdomen, T5, hair color
      Primarily white, with dark hairs found only apicomedially (californica)
      Primarily dark, or if about equal in density then with the light hairs limited to the lateral sides of T5 (americana, eickworti, melittoides)

      If you've read over the characters and found anything questionable, or have any suggestions for either diction changes or additional characters, please contact either myself (mco25@...) or Sam Droege (sdroege@...). We only have so many specimens of each species available to us, so we always welcome any user feedback that might benefit the resolving power or clarity of the guides.


      -Michael Orr

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