www.photomacrography.net :: View topic - Madagascar part XX
www.photomacrography.net Forum Index
An online community dedicated to the practices of photomacrography, close-up and macro photography, and photomicrography.
Photomacrography Front Page Amateurmicrography Front Page
Old Forums/Galleries
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Madagascar part XX

 
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> Nature Photography -- Macro and Close-up
View previous topic :: View next topic  
Author Message
pbertner



Joined: 02 Mar 2010
Posts: 833
Location: Canada

PostPosted: Sat Jan 23, 2016 3:40 am    Post subject: Madagascar part XX Reply with quote

1) Madagascar day gecko (Phelsuma lineata) with prey:



2) Praying mantis:



3) Fulgorid hopper nymph (Belbina sp.):



4) Spiny leaf beetle black and white:



5) Carpenter ant (Camponotus sp.):



6) Microhylid frog (Platypelis tuberifera):



7)


8. Stick insect portrait:



9) Froglet camouflaged as bird dung (Boophis sp.):



10) Mating big headed flies (Pipunculidae):



Thanks for looking and commenting,
Paul
_________________
Paul
https://rainforests.smugmug.com/
http://www.flickr.com/photos/31137609@N08/
http://pbertner.wordpress.com/
Back to top
View user's profile Send private message Send e-mail Visit poster's website AIM Address
JH



Joined: 09 Mar 2013
Posts: 735
Location: Vallentuna, Stockholm, Sweden

PostPosted: Sat Jan 23, 2016 4:22 am    Post subject: Reply with quote

Interesting and very nice!
Regards Jörgen
Back to top
View user's profile Send private message Visit poster's website
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 17417
Location: Richland, Washington State, USA

PostPosted: Sat Jan 23, 2016 10:44 am    Post subject: Reply with quote

Nicely shot, as always.

Very obvious difference in the eyes of the male and female at 10) Mating big headed flies (Pipunculidae).

Any idea what difference in behavior might explain that? The ones on the lower beast (female?) look like they're optimized for high resolution looking straight ahead, maybe better for some sort of pursuit?

--Rik
Back to top
View user's profile Send private message Visit poster's website
Ichthyophthirius



Joined: 07 Mar 2013
Posts: 610

PostPosted: Sun Jan 24, 2016 9:21 am    Post subject: Reply with quote

Beatiful pictures!

rjlittlefield wrote:
Very obvious difference in the eyes of the male and female at 10) Mating big headed flies (Pipunculidae).

Any idea what difference in behavior might explain that? The ones on the lower beast (female?) look like they're optimized for high resolution looking straight ahead, maybe better for some sort of pursuit?


The larger ommatids in the front of the female's eyes usually mean lower resolution and higher light-gathering ability (night-flying).

I couldn't find information about the purpose. May it's got something to do with the female's search for host to lay its eggs?
Back to top
View user's profile Send private message
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 17417
Location: Richland, Washington State, USA

PostPosted: Sun Jan 24, 2016 12:45 pm    Post subject: Reply with quote

Ichthyophthirius wrote:
The larger ommatids in the front of the female's eyes usually mean lower resolution

I would be interested to see a reference on that. The ones I have on hand say exactly the opposite.

For example, R.F. Chapman, "The Insects / Structure and Function", 4th edition, page 590:
Quote:
The form and arrangement of ommatidia differs in different parts of the eye in many, and perhaps all, insects. For example, in the praying mantis, Tenodera, the facet diameter is greatest in the forwardly directed part of the eye, and decreases all round (Fig 22.4). Because the radius of curvature of this same part of the eye is greater (so the surface is flatter) than elsewhere, the angle between the optical axes of adjacent ommatidia (the interommatidial angle) is less than elsewhere and the rhabdoms are longer, but thinner. This area of the eye is functionally equivalent to the vertebrate fovea (see below) and similar regions are known to be present in the eyes of other insect species with a particular need for good resolution.


Michael F. Land, in "Visual Acuity in Insects", page 159 (pdf page 13 of 31):
Quote:
In general, the only realistic way that a compound eye can achieve resolution much better than a degree is to build in an "acute zone" -- a small region with larger facets and higher acuity (23,38). We shall see that this is a very common strategy.


I notice in this image that the small area with large ommatidia is also flatter, so it seems quite a good match to Chapman's and Land's descriptions.

--Rik
Back to top
View user's profile Send private message Visit poster's website
pbertner



Joined: 02 Mar 2010
Posts: 833
Location: Canada

PostPosted: Sun Jan 24, 2016 1:30 pm    Post subject: Reply with quote

Thanks Rik, Ichthyophthirius and Jorgen, much appreciated.

Glad you took the initiative on finding that out Rik as I didn't know. Indeed the female's pursuit for a host seems like the most logical explanation. Interesting that the difference is also demarcated in colour too.
_________________
Paul
https://rainforests.smugmug.com/
http://www.flickr.com/photos/31137609@N08/
http://pbertner.wordpress.com/
Back to top
View user's profile Send private message Send e-mail Visit poster's website AIM Address
Ichthyophthirius



Joined: 07 Mar 2013
Posts: 610

PostPosted: Sun Jan 24, 2016 2:06 pm    Post subject: Reply with quote

Hi Rik,

My understanding was that the highest resolution in insects is associated with the highest density of ommatidia (dragonflies). The chapter by Land (1997) is very interesting; there is obviously a huge body of knowledge about compound eyes.

This is what I was thinking of (p. 171):
"An increase in the detectability of small objects can be achieved either by reducing ?p, so that a small target causes a large change in the signal on the rhabdom that images it, or by increasing the numbers of photons available to the rhabdoms, thereby reducing the noise against which the signal must be detected. Either method requires a larger facet diameter D (Equation 7 and 11). In most known examples increases in facet diameter have evolved to reduce ?p. However, the male blowfly Chrysomyia megalocephala has a “bright zone” rather than an acute zone, where ?p is similar to the rest of the eye, but the photon catch per rhabdomere is enhanced roughly tenfold by an increase in both facet and rhabdomere diameter (81). Perhaps this enables the fly to mate in particularly dim conditions."

So maybe I was wrong.
Larger ommatidia mean fewer pixels and therefore lower resolution.
However, the insect can use the larger ommatidia
a) for larger photon catch (lower resolution but brigher image)
b) reduce the ?p (acceptance angle) of each ommatidium (better quality of each pixel and therefore potentially better image quality overall)

BTW, I found the big-headed flies on the same page:
"Although it is males that generally have acute zones, females of the pipunculid flies in the genus Chalarus, have greatly enlarged frontodorsal ommatidia (27). These flies parasitize leafhoppers, and the ovipositing females must locate these on the undersides of leaves. The males have no equivalent need for keen eyesight."

Kind regards,

Ichty
Back to top
View user's profile Send private message
rjlittlefield
Site Admin


Joined: 01 Aug 2006
Posts: 17417
Location: Richland, Washington State, USA

PostPosted: Sun Jan 24, 2016 3:14 pm    Post subject: Reply with quote

Ichthyophthirius wrote:
Larger ommatidia mean fewer pixels and therefore lower resolution.

Fewer pixels yes, but that means lower resolution only if the visual angle covered remains the same. My understanding is that in these flatter areas with larger ommatidia, the visual angle drops more than the pixel count does, leading to higher resolution in an angular sense.

Quote:
the highest resolution in insects is associated with the highest density of ommatidia (dragonflies)

Again, we need to be careful about "density". Dragonflies have a high density of ommatidia in the angular sense, but that is spread across a very large eye to give a low density in terms of area. The eyes of fruit flies have much higher density in terms of ommatidia per mm, but much less in terms of ommatidia per radian. Compare the 1 mm wide section of dragonfly eye at http://www.photomacrography.net/forum/viewtopic.php?t=11271 against the 0.5 mm entire fruit fly eye at http://www.photomacrography.net/forum/viewtopic.php?t=7379.

--Rik
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> Nature Photography -- Macro and Close-up All times are GMT - 7 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group