Readers’ Wildlife Photos: Arthropods

July 27, 2015 • 8:30 am

Mark Sturtevant has sent us on some more great photographs and commentary to go along with them.

 

Here is yet another installment of budget close-up photography of local arthropods. I am having a wonderful summer doing this, and I think I am slowly getting better at my hobby. The pictures are numbered in the order of my comments here.

A stink bug nymph, possibly in the genus Apoecilus, feeding on an eastern tent caterpillar (Malacosoma americanum). In this picture you can see something of how a piercing-sucking proboscis works in insects. The proboscis is really homologous to the generalized chewing mouth parts of other insects. The thick, jointed part under the head that is bent aside is the labium (which is like a lower lip), while the thin whitish line seen entering the labium is really a bundle of piercing, needle-like mouth parts that are the mandibles and maxillae. The labium guides the piercing mouth parts into the prey, and those piercing mouth parts alternately pump up and down to scissor their way deeper into flesh. Digestive juices are pumped in, and the insect slurps up a liquid meal. The design is seen here:

Interestingly, the piercing mouth parts of some other insects like mosquitoes are very similar, and so this should be a good example of convergent evolution.

1StinkBugEating

Marsh fly (Tetanocera). I do not have a lot to say about this one except that I am finding that many largish flies do not mind if a big camera lens draws in close to take pictures. I also like all the hairs since that makes ‘em interesting.

2MarshFly

Six spotted orbweaver, Araniella displicata. This pretty little spider is so-named because it has six spots on the dorsal side of its abdomen. According to Bug Eric in this post: it is actually very common for this spider to spin a small orb web within the curl of a single leaf, as this one has done here.

3SixSpotSpider

Male harvestman (Phalangium opilio). One can recognize this to be a male by its elongated pedipalps. This widespread species is described as the most widely distributed harvestman in the world, and so possibly every reader of WEIT on every continent has seen this small, harmless species of harvestman. Well, harmless to humans. I have seen these animals eating surprisingly large insects.

 

4MaleHarvestman

24 thoughts on “Readers’ Wildlife Photos: Arthropods

  1. I’m always amazed by the strength that insects seem to have. The stink bug above must weigh quite a bit less than its food, and seems to barely be gripping it!

    I was going to ask about weight-to-strength ratio in insects but I imagine that varies quite wildly so instead I searched around and found something on Onthophagus taurus. http://blogs.scientificamerican.com/observations/worlds-strongest-animal-effectively-benches-1000-times-its-body-weight/

    The article says that the males in this particular species of dung beetle are able pull things up to 1,141 times their own body weight. However this was not the most interesting part of the article. It seems that there are some weaker males who can move faster than their stronger brethren and have “super-dense testes”:

    “But not every male O. taurus is a super-strong prizefighter. Some males are not as big and strong as their big-horned fellows. Instead, these males are fast walkers with super-dense testes, who can sneak into the females’ tunnels, avoiding the so-called “major” males altogether. Once alone with the female, they use their higher sperm count to up their chances at impregnating her in their single shot.

    “These different behaviors generate different selective pressures for the two morphs,” Knell and his colleague Leigh Simmons, of the School of Animal Biology at the University of Western Australia in Crawley, wrote.”

    I believe there is a species of squid or octopus whose males use different mating strategies depending on their size. Are there many other animals that do this?

    1. I have read a little on dung beetle testes, which are generalized as being relatively huge. I did not know about the different kinds of testes.
      It is a common strategy in nature where males compete with other males for their to be more than one kind of male. This is not just a dung beetle thing. As a rough rule, some males are big and aggressive and win access to females by direct male-on-male combat and holding a large territory. This takes a lot of energy. Other males are smaller and ‘sneaky’. The 2nd kind of dung beetle is sort of like the latter kind of male, maybe.

        1. No, more like jock/nerd who counts on actually (or hopefully) attracting a female, versus stalker/rapist.

          Where do people get the idea that nerds aren’t sexy?

  2. Thanks for the morphology of the proboscis; it is always fascinating to see how similar structures (like mandible and maxilla) have evolved for specific purposes across many species. Also, does the adult stinkbug only eat sap from vegetation (this is my inkling)? I find it interesting that the nymph eats other insects, but metamorphosis into a ‘vegetarian’. Or perhaps there are insect eating stinkbugs and this is an example of one and as an adult it also eats insects. hmmmm

    For some reason I thought Harvestmen (Daddylong legs, right?) could bite humans and have a potent venom. In my mind’s eye (or nose’s eye) I can recall their pungent stench.

    Great macro photography as well, you’ve captured some really cool subjects this Summer.

    1. Some stink bugs species are plant feeders, and others are predatory. I do not think they change their diet as they grow.
      It would be news to me to learn that a harvestman can give a painful bite. Their chelicerae are tiny little pincers, and they just do not have the muscles for it. But they come in a very large range of forms (some are among the weirdest looking arthropods) and so on introspection I would not rule out that there is some species I have not seen that can give a good chomp.

  3. Thanks for the description of the mouth parts for the insects. I always imagine it as sucking up the insides like a yummy milkshake.

    I especially like the picture of the harvestman.

  4. My only harvestman story, re-posted from another site:

    In Richmond, Va., ca. 1984, a harvestman came to visit the cement slab of our apartment’s back porch. The wife & I were having dinner at the time, and the wife took a tiny meat bit from our spaghetti sauce and put it out where the harvestman could find it. The creature _did_ find the bit, _picked it up_ and _walked away with it_.

    My jaw didn’t snap back into place until three days later.

      1. Sweets I’d guess would be for nectar-lovers, viz., vegetarians. But I wouldn’t place a bet on it. I was surprised once. 🙂

    1. In Richmond, they’re called Daddy Long Legs. As a child, I used to pick them up, one at a time, and let it crawl up my arm. Then, I’d raise my arm in the air, and it would continue crawling upward, this time to my hand. Then, of course, I’d lower my arm, again. It was sort of like a slow yo-yo.

Leave a Reply