[Odonata-l] Fwd: Ophiogomphus head damage

[Dennis Paulson]

Nick, I haven't seen the marks you speak of, but I'll have to look  
for them. If they are on Ophiogomphus, I assume they are on other  
genera.

When you look at the hooks and bumps and spines on the appendages of  
many male odonates, it's not surprising that there is female head  
damage, especially when you think they have to hold on pretty tightly  
when they're flying around in cop. I suppose all the little bumps and  
spines under the cerci of many libellulids are sort of a nonskid  
apparatus, but do they leave marks on the females? The cerci of  
species such as Arigomphus cornutus and Octogomphus specularis look  
like lethal weapons. Do they leave bigger scars? Philip Calvert  
described in detail the hooking up of the complicated appendages of  
male Epigomphus with their females (Calvert, P. P. 1920. The Costa  
Rican species of Epigomphus and their mutual mating adaptations  
(Odonata). Trans. Amer. Ent. Soc. 46: 323-354.). At the same time, as  
it may not be in the female's best interest to have her head pierced,  
you'd think her cuticle would be strengthened at those points. Or is  
there some positive consequence of the "mating marks" on females, for  
example those on the eyes of aeshnids that Sid Dunkle described  
(Dunkle, S. W. 1979. Ocular mating marks in female Nearctic Aeshnidae  
(Anisoptera). Odonatologica 8: 123-127.) and can be found on a  
variety of female anisopterans?

To me an interesting question is why cerci should have spines or  
hooks on the dorsal surface, which presumably doesn't contact the  
female. Does the projection on the top of the cercus in something  
like Epitheca canis serve any function? Does it touch the female  
somewhere? Mark McPeek is doing all this interesting scanning of  
cerci in damselflies, but I think someone should be looking more  
closely at the situation in anisopterans as well. Mating pairs of  
anisopterans should be collected and somehow preserved in tandem,  
even with the female's head detached from her body. As the connection  
is only on the head, it might be easier to understand than the  
perhaps more complex connection of male zygopteran appendages with  
both the female prothorax and mesostigmal laminae. And we need a good  
assessment of the sensillae that are presumably present in the female  
to tell her that the male appendages "feel right."

When I see the amazing amount of variation in the complicated  
appendages of male odonates, I often wonder how those of each species  
could possibly hook up to the female's head or thorax and whether the  
varied shapes are a consequence of selection for reproductive  
isolation or a varied response to holding on tightly. Within a genus  
of libellulids, the appendages are often fairly similar, but then  
they may be quite different in another genus. Why? Some adaptations  
seem obvious, like the long, simple cerci of male Tramea, used for  
quick reattachment to the female after each oviposition dip. Most  
others aren't so obvious.


On Mar 21, 2008, at 2:27 PM, Dennis Paulson wrote:

> Begin forwarded message:
>
>> From: "Nick and Ailsa Donnelly" <tdonelly at binghamton.edu>
>> Date: March 21, 2008 2:09:18 PM PDT
>> To: <dennispaulson at comcast.net>
>> Subject: To be posted on the list serve
>>
>>
>> Damage to rear of female heads of Ophiogomphus.
>>
>> Recently I have been removing the heads of several species of  
>> Ophiogomphus
>> to examine the rear.  I have noticed some damage, which I can best  
>> describe
>> as crude near-vertical elongate indentations, usually with small  
>> scrape
>> marks.  I first thought these were something I was doing while  
>> removing the
>> heads, but I now think that they are older, and probably existed  
>> during the
>> life of the female.  Perhaps the pressure of the cerci (which lie  
>> on th
>> erear of the head) is more important than I had thought in  
>> maintaining the
>> grab of the close-fitting eprproct on the face.  Has anyone ese  
>> wondered
>> about these marks?
>>
>> It seems pretty clear that tandem pairing removes most of the  
>> hairs on the
>> female occiput by rubbing (teneral females are quite hirsute, but  
>> older
>> females have few hairs left), and I believe the horns on the  
>> occiput are
>> often broken right off.  But these marks on the rear of the head  
>> baffle me,
>> unless they are the marks left by  the medial edge of the cercus.
>>
>> Nick Donnelly
>
>

-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
dennispaulson at comcast.net



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