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Index of Subjects --Apple-Mail-92-120354520 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Hi Angus, On 7-Apr-07, at 9:12 PM, Angus MacLean wrote: > I know, it's not fly season yet but I have been reviewing some > pictures from last fall and would appreciate any input. > > Most of these photos are of Eristalis transversa but I wonder about > the white (rather than orange) abdomen banding. Is this a mark of > age or of gender (i.e. male). The "white" banding that is visibile in these photos at the junctures of the abdominal segments appears to be intersegmental tissue. This is the flexible tissue between the hard tergal and sternal plates that allow the insect to flex and move its abdomen. If my experience with beetles is any guideline, how much (if any) of this intersegmental tissue is visible depends on both the position of the abdomen (whether its is in a straight position or is bent), and how full the abdomen is. For instance, if the insect has eaten or drank a lot, the abdomen swells and more of this intersegmental tissue (which is typically pale in comparison to the coloration of the terga or sterna) is visible. I think these factors are probably responsible for the variability of this white "banding." > Also none had a orange scutellum (that half circle at the rear of > the thorax). Do all eventually acquire this? No idea. > > There are six photos of transversa. Double-click for a larger pic. > > http://www.flickr.com/photos/58321572@N00/ > > Another one appears different and I think it is E. dimidiatus. > Anyone confirm this or have other ideas? > It does look very much like Eristalis dimidiatus, which is a common species in Nova Scotia. Cheers! Chris _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._. _. Christopher Majka - Nova Scotia Museum of Natural History 1747 Summer Street, Halifax, Nova Scotia, Canada B3H 3A6 (902) 424-6435 Email <c.majka@ns.sympatico.ca> _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._. _. --Apple-Mail-92-120354520 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1 <HTML><BODY style=3D"word-wrap: break-word; -khtml-nbsp-mode: space; = -khtml-line-break: after-white-space; ">Hi Angus,<DIV><SPAN = class=3D"Apple-style-span"><BR><DIV><DIV>On 7-Apr-07, at 9:12 PM, Angus = MacLean wrote:</DIV><BR class=3D"Apple-interchange-newline"><BLOCKQUOTE = type=3D"cite"><DIV style=3D"margin-top: 0px; margin-right: 0px; = margin-bottom: 0px; margin-left: 0px; ">I know, it's not fly season yet = but I have been reviewing some pictures from last fall and would = appreciate any input.</DIV><DIV style=3D"margin-top: 0px; margin-right: = 0px; margin-bottom: 0px; margin-left: 0px; min-height: 14px; = "><BR></DIV><DIV style=3D"margin-top: 0px; margin-right: 0px; = margin-bottom: 0px; margin-left: 0px; ">Most of these photos are of = Eristalis transversa but I wonder about the white (rather than orange) = abdomen banding. Is this a mark of age or of gender (i.e. male). = <BR></DIV></BLOCKQUOTE><DIV><BR = class=3D"khtml-block-placeholder"></DIV><DIV>The "white" banding that is = visibile in these photos at the junctures of the abdominal segments = appears to be intersegmental tissue. This is the flexible tissue between = the hard tergal and sternal plates that allow the insect to flex and = move its abdomen. If my experience with beetles is any guideline, how = much (if any) of this intersegmental tissue is visible depends on both = the position of the abdomen (whether its is in a straight position or is = bent), and how full the abdomen is. For instance, if the insect has = eaten or drank a lot, the abdomen swells and more of this intersegmental = tissue (which is typically pale in comparison to the coloration of the = terga or sterna) is visible. I think these factors are probably = responsible for the variability of this white = "banding."</DIV><BR><BLOCKQUOTE type=3D"cite"><DIV style=3D"margin-top: = 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Also = none had a orange scutellum (that half circle at the rear of the = thorax). Do all eventually acquire this?</DIV></BLOCKQUOTE><DIV><BR = class=3D"khtml-block-placeholder"></DIV><DIV>No = idea.</DIV><BR><BLOCKQUOTE type=3D"cite"><DIV style=3D"margin-top: 0px; = margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: = 14px; "><BR></DIV><DIV style=3D"margin-top: 0px; margin-right: 0px; = margin-bottom: 0px; margin-left: 0px; ">There are six photos of = transversa. Double-click for a larger pic.</DIV><DIV style=3D"margin-top: = 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; = min-height: 14px; "><BR></DIV><DIV style=3D"margin-top: 0px; = margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><A = href=3D"http://www.flickr.com/photos/58321572@N00/">http://www.flickr.com/= photos/58321572@N00/</A></DIV><DIV style=3D"margin-top: 0px; = margin-right: 0px; margin-bottom: 0px; margin-left: 0px; min-height: = 14px; "><BR></DIV><DIV style=3D"margin-top: 0px; margin-right: 0px; = margin-bottom: 0px; margin-left: 0px; ">Another one appears different = and I think it is E. dimidiatus. Anyone confirm this or have other = ideas?</DIV><DIV style=3D"margin-top: 0px; margin-right: 0px; = margin-bottom: 0px; margin-left: 0px; min-height: 14px; = "><BR></DIV></BLOCKQUOTE></DIV><DIV><BR = class=3D"khtml-block-placeholder"></DIV>It does look very much like = <I>Eristalis dimidiatus,</I> which is a common species in Nova = Scotia.</SPAN></DIV><DIV><BR = class=3D"khtml-block-placeholder"></DIV><DIV>Cheers!</DIV><DIV><BR = class=3D"khtml-block-placeholder"></DIV><DIV>Chris<BR><DIV> <P = style=3D"margin: 0.0px 0.0px 0.0px 0.0px"><FONT face=3D"Times" size=3D"3" = style=3D"font: 12.0px = Times">_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._= ._._._.</FONT></P> <P style=3D"margin: 0.0px 0.0px 0.0px 0.0px"><FONT = face=3D"Times" size=3D"3" style=3D"font: 12.0px Times">Christopher Majka = - Nova Scotia Museum of Natural History</FONT></P> <P style=3D"margin: = 0.0px 0.0px 0.0px 0.0px"><FONT face=3D"Times" size=3D"3" style=3D"font: = 12.0px Times">1747 Summer Street, Halifax, Nova Scotia, Canada<SPAN = class=3D"Apple-converted-space">=A0 </SPAN>B3H 3A6</FONT></P> <P = style=3D"margin: 0.0px 0.0px 0.0px 0.0px"><FONT face=3D"Times" size=3D"3" = style=3D"font: 12.0px Times"