[NatureNS] Harvestmen (opilionids)

From: Christopher Majka <c.majka@ns.sympatico.ca>
To: naturens@chebucto.ns.ca
Date: Wed, 21 May 2008 19:28:38 -0300
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Hi Ken,

On 21-May-08, at 12:06 PM, Ken MacAulay wrote:

> Thanks, Chris.  You are a fount of information, as usual!  I notice  
> on the first "harvestman" pic that it appears to have pairs of  
> spikes on its back and along the "feelers" (?).  Are these a  
> defensive mechanism?  I haven't noticed such in our local harvestmen  
> who seem to have a smooth body, at least the ones I have seen.

What you see in that picture is a harvestman (opilionid) using the  
hind six legs for walking while holding the front pair of legs folded  
in front of the head (using six legs for locomotion is a frequent  
feature of harvestmen). Visible inside of these are a pair of so- 
called pedi-palps, which are sensory appendages. Not terribly visible  
in that photo, are the two chelicerae which are claw-like appendages  
that are situated inside of the pedi-palps which are used in  
manipulating food. To see these more clearly take a look at the photo  
below which shows an opilionid with massive pedi-palps and chelicerae

http://k53.pbase.com/g6/23/341923/2/73138210.mAridpxX.jpg

The species pictured in the first photo does have six spines on the  
abdomen and a series of spines on the front legs and/or pedi-palps  
(its hard to make out which). I think its probably a safe assumption  
that these have some defensive function. The morphology of opilionids  
is varied and most of the ones (at least in this region) do not have  
such spines. C.D. Dondale (in Canada and its Insect Fauna) recorded 47  
species of opilionids in Canada. I've no idea how many of these occur  
in Nova Scotia

Most harvestmen feed on plant juices or dead insects, although some  
also feed on living insects. In general they are found in moist  
environments.

Cheers!

Chris

> Ken MacAulay

Christopher Majka
Nova Scotia Museum, 1747 Summer St., Halifax, Nova Scotia, Canada  B3H  
3A6
c.majka@ns.sympatico.ca




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<html><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
-webkit-line-break: after-white-space; ">Hi Ken,<div><br><div><div>On =
21-May-08, at 12:06 PM, Ken MacAulay wrote:</div><br =
class=3D"Apple-interchange-newline"><blockquote type=3D"cite"> <div> =
<div><span class=3D"015120415-21052008"><font face=3D"Arial" =
color=3D"#0000ff" size=3D"2">Thanks, Chris.&nbsp; You are a fount of =
information, as usual!&nbsp; I notice on the first "harvestman" pic that =
it appears to have pairs of spikes on its back and along the "feelers" =
(?).&nbsp; Are these a defensive mechanism?&nbsp; I haven't noticed such =
in our local harvestmen who seem to have a smooth body, at least the =
ones I have =
seen.</font></span></div></div></blockquote><div><br></div><div>What you =
see in that picture is a harvestman (opilionid) using the hind six legs =
for walking while holding the front pair of legs folded in front of the =
head (using six legs for locomotion is a frequent feature of =
harvestmen). Visible inside of these are a pair of so-called pedi-palps, =
which are sensory appendages. Not terribly visible in that photo, are =
the two chelicerae which are claw-like appendages that are situated =
inside of the pedi-palps which are used in manipulating food. To see =
these more clearly take a look at the photo below which shows an =
opilionid with massive pedi-palps =
and&nbsp;chelicerae</div><div><br></div><div><a =
href=3D"http://k53.pbase.com/g6/23/341923/2/73138210.mAridpxX.jpg">http://=
k53.pbase.com/g6/23/341923/2/73138210.mAridpxX.jpg</a></div><div><br></div=
><div>The species pictured in the first photo does have six spines on =
the abdomen and a series of spines on the front legs =
and/or&nbsp;pedi-palps (its hard to make out which). I think its =
probably a safe assumption that these have some defensive function. The =
morphology of opilionids is varied and most of the ones (at least in =
this region) do not have such spines. C.D. Dondale (in Canada and its =
Insect Fauna) recorded 47 species of opilionids in Canada. I've no idea =
how many of these occur in Nova Scotia</div><div><br></div><div>Most =
harvestmen feed on plant juices or dead insects, although some also feed =
on living insects. In general they are found in moist =
environments.&nbsp;</div><div><br></div><div>Cheers!</div><div><br></div><=
div>Chris</div><div><br></div><blockquote type=3D"cite"><div> <div><span =
class=3D"015120415-21052008"><font face=3D"Arial" color=3D"#0000ff" =
size=3D"2">Ken =
MacAulay</font></span></div></div></blockquote></div><br><div =
apple-content-edited=3D"true"> <span class=3D"Apple-style-span" =
style=3D"border-collapse: separate; border-spacing: 0px 0px; color: =
rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: =
normal; font-variant: normal; font-weight: normal; letter-spacing: =
normal; line-height: normal; text-align: auto; =
-khtml-text-decorations-in-effect: none; text-indent: 0px; =
-apple-text-size-adjust: auto; text-transform: none; orphans: 2; =
white-space: normal; widows: 2; word-spacing: 0px; "><div =
style=3D"word-wrap: break-word; -khtml-nbsp-mode: space; =
-khtml-line-break: after-white-space; "><div>Christopher =
Majka</div><div>Nova Scotia Museum, 1747 Summer St., Halifax, Nova =
Scotia, Canada&nbsp; B3H 3A6</div><div><a =
href=3D"mailto:c.majka@ns.sympatico.ca">c.majka@ns.sympatico.ca</a></div><=
div><br class=3D"khtml-block-placeholder"></div></div><br =
class=3D"Apple-interchange-newline"></span> =
</div><br></div></body></html>=

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