The thing in the pits

You leave your home in the morning, as you do every day. On your way to work, you walk past a deep, conical pit, dug in fine sand, with smooth edges that lead to a small cavity at the bottom. As you continue walking, you notice more of these pits; they vary in size, but they are all the same shape.

The pits

Soon, you get too close to the edge of one of the pits, and a flurry of rocks blast from the bottom of the pit and hit your legs; before you know it, you’re tumbling down the sides of the pit, and if you try to slow yourself down and scale the smooth surface back to the top, you’re hit with another wave of rocks thrown at you from the center of the pit. Finally, you reach the bottom, where you can only see them when it’s too late: Two massive jaws, each with several sharp, pointed teeth, grab your sides and a creature you can’t see starts eating you while you’re still alive.

While this may seem like the plot for a SyFy original movie, this is a common occurrence in the insect world. The unfortunate creature that met its demise at the bottom of the pit is an ant, and the undescribed monster with the massive jaws is an antlion larva.

The thing in the pits

Antlions belong to the family Myrmeleontidae in the order Neuroptera, and its closest relatives, the lacewings and owlflies (Chrysopidae and Ascalaphidae, respectively) also have predatory larvae. However, they are active hunters, unlike antlion larvae; these dig conical pits in fine sand and wait for ants or other small arthropods to walk close to the edge, and when one does, they fling grains of sand at them until they tumble down the pit and into their massive jaws.

Now, as you can see in the above pic, they are basically huge abdomens with massive scissor-jaws. So how can they possibly hide? Easy: they have fine hairs all over their body that trap dust and sand, and then they bury themselves deep until only part of the jaws are visible at the bottom of the pit. Once buried, they wait motionless for an unsuspecting prey to walk by.

Of course, they’re very easy to see once they’re on a white surface and (somewhat) clean:

But place them on soil, and they immediately cover themselves with it and are notoriously hard to spot unless they move:

I enjoy seeing these larvae because they are a) Visually awesome and b) They show spectacular behavior when they’re capturing prey. I definitely wouldn’t want to be a small arthropod near one of these pits, particularly when I know what’s at the bottom!

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Limping around

The thought of us humans losing a limb is catastrophic, but some insects can shrug it off, or at least to some extent.

Stick insects (order Phasmatodea) are able to regenerate limbs without apparent tradeoffs [1], but insects such as mantids aren’t so lucky. Limb regeneration can ocurr if it is severed during early instars, but the limb will have four tarsi instead of five and will usually be shorter [2].

I was able to witness this during my latest field trip with a female Stagmatoptera. Notice that the left hind leg is shorter:

image

image

The atrophied leg didn’t appear to hinder the insect’s movement, although I did notice it moving slower than males of the same species. This may be due to the males being thinner and not as heavy as the female, though.

1.- Maginnis, T. & Redmond, C., 2009. Leg Regeneration Trade-Offs in the Twostriped Walkingstick (Phasmatodea: Pseudophasmatidae). Annals of the Entomological Society of America: Vol. 102, Issue 6, pg(s) 1099-1104 doi: 10.1603/008.102.0618
2.- Ramsay, G.W. 1990. Mantodea (Insecta), with a review of aspects of morphology and biology. Fauna of New Zealand, No 19

Wasp-mimicking katydids

Imagine yourself in a tropical jungle. You see a medium sized insect, about 3.5 cm long, land on a light trap. Its body is elongated, metallic black with a bluish hue, bright orange wings and long orange and black antennae. It walks around moving its antennae really fast. What could it be?

– “Dan, It’s a tarantula hawk, a wasp in the family Pompilidae, duh!

Not so fast! In the insect world, things aren’t always what they seem, and this is a fine example:

Aganacris

This jaw-dropping katydid (Tettigoniidae; Phaneropterinae) belongs to the genus Aganacris, and it mimics a pompilid wasp (Pepsis are relatively common here and have very similar colors) with remarkable accuracy. Aposematic wasp mimics are common in the insect world; you can see many examples in flies (Syrphidae), moths (Sesiidae) and beetles (Cerambycidae), but seeing it in a katydid was a first. As it turns out, wasp mimicry in tettigonids is pretty rare; Nickle and Castner studied the strategies against diurnal predators used by this group in Perú, and most of the groups were leaf/bark/twig/lichen mimics; only two genera, Aganacris and Scaphura, were found to be wasp mimics. [1]

This is another first for me (I mentioned pentatomids making insect smoothies earlier), and I couldn’t be happier. Even though I’ve been to this particular biological station quite a few times, every time I go there I see something new and simply astonishing.

1.- David A. Nickle and James L. Castner, 1995. Strategies Utilized by Katydids (Orthoptera: Tettigoniidae) against Diurnal Predators in Rainforests of Northeastern Peru. Journal of Orthoptera Research, No. 4, pp. 75-88. http://www.jstor.org/stable/3503461

The impaler

There are always outsiders in entomology, groups that don’t follow the norm. We’re taught, for example, that stink bugs are herbivorous (and often pests), that some feed on nitrogen-rich reproductive parts of plants while others feed on somatic tissue. So when you see a pentatomid on a light trap, you might think “How cute, look at this little bug! I wonder if there’s a plant around here it might feed on“. Then along comes the nasty little critter and impales a moth like it’s a scene from 300:

The poor moth never stood a chance

The poor moth never stood a chance

One might think it’s a fluke and not a regular occurrence, but then the next night you see the same thing, only this time it’s a poor ant that gets eaten:

Ant on a stick

As it turns out, there’s an entire subfamily of stink bugs (Pentatomidae: Asopinae) that is predatory, and it has been used as a pest control agent [1]. While its entomophagous habits are pretty well documented, I had never actually seen one. Finding out that some stink bugs make insect smoothies was one of the highlights of my recent jungle trip; I’ll leave the other ones for future blog posts!

1.- Robert G. Foottit and Peter H. Adler, 2009. Insect Biodiversity: Science and Society. Blackwell Publishing Ltd. ISBN: 978-1-405-15142-9 Chapter 10: Biodiversity of Heteroptera – Thomas J. Henry

Pre-NMW 2013

We are currently in the middle of National Moth Week, and I am organizing a mothing event in a biological station (trying to, at least; I was supposed to leave yesterday but I had car trouble). I’ve been there several times and the moth diversity is astonishing: big/small, colorful/inconspicuous, with pointy or rounded wings, they’re all there.  I’d like to show you a few specimens that you can find there; I focused on macrolepidopterans when I took pictures, because they were less skittish than microleps.

A classic Automeris

A classic Automeris

Who said moths had dull colors?

Who said moths had dull colors?

Wasp mimics are a common sight at the light trap

Wasp mimics are a common sight at the light trap

Patterns and markings abound

Patterns and markings abound

Like I said, plenty of wasp mimics!

Like I said, plenty of wasp mimics!

And finally, one of my personal favorites, the Dog-faced moth:

Looks like a dachshund or a basset hound

Looks like a dachshund or a basset hound

This is barely a small fraction of the astonishing moth diversity you can find there (not to mention other arthropods), and I hope to be able to photograph and collect a lot more that I have in past visits. If everything goes well and I manage to go, I’ll write a post-NMW 2013 post sometime next week after processing data and images.

 

 

Peculiar hitchhikers

Phoresis has been well studied interaction in biology, and it has been reported in both vertebrates and invertebrates. An example of vertebrate phoresis is the remora (Perciformes: Echeneidae), whose first dorsal fin is modified into an oval sucker that allows it to attach itself to larger marine animals, and one example I’ve seen often in invertebrates is pseudoscorpions on beetles, particularly longhorns (Cerambycidae). But I recently learned that phoresis in invertebrates is a world about which I know nothing.

We collected some beetles in the Andes a few weeks ago. Nothing too eye-catching, just some scarabaeids that landed on the light trap. We collected a few and didn’t think much about them after that, so they stayed in a jar at the lab. I reviewed the contents of the jar earlier this week and saw something interesting: about 30-40 mites were floating around in the alcohol, and two beetles had this:

Beetle is roughly 3 cm long

Beetle is roughly 3 cm long

I didn’t recognize these structures, at least not on a beetle we captured alive. We had seen molds on dead beetles that had a similar overall shape, but there was one catch: molds don’t have legs!

Definitely not a mold!

Definitely not a mold!

I did what I usually do when I’m stumped and have no immediate access to my books/computer: I turned to Twitter for help. Sure enough, I soon received replies regarding these animals. Christopher Taylor (@CatOfOrgidentified them as phoretic Uropodina mite deutonymphs, and gave some insight as to what that stalk-like structure was. After that, Wayne Knee (@whknee) added that these mites use liquid glue, and form the pedicel by moving ahead, and that the mite later detaches, leaving the pedicel behind.

Sure enough, I found that different mites have different types of pedicels: they can be long, short, irregularly shaped, straight or helically coiled, and they can be homogenous or formed by packed bundles of fibers [1]. These are to assure successful phoresis on their hosts. I also found that host selection can be either very specific (one single species of centipede [2]) or non-specific (25 different species of beetles from several families [3]), but in both studies there appears to be a tendency for selecting specific body parts from which to attach the pedicel.

For the second time this week, I was stumped by arthropods (the first time was by some odd little things), which I really enjoy, for it means I’m always learning something new! And, again, it proves that Twitter can be an excellent tool for learning and sharing information.

1.- Bajerlein, D., et al., Morphological diversity of pedicels in phoretic deutonymphs of Uropodina mites (Acari: Mesostigmata), Arthropod Structure & Development (2013), http://dx.doi.org/10.1016/j.asd.2013.02.002

2.- Bloszyk, J., Klimczak, J. & Lesniewska, M., Phoretic relationships between Uropodina (Acari: Mesostigmata) and centipedes (Chilopoda) as an example of evolutionary adaptation of mites to temporary microhabitats, Eur. J. Entomol. 103: 699–707, 2006

3.- Bajerlein, D. & Bloszyk, J., Phoresy of Uropoda orbicularis (Acari: Mesostigmata) by beetles (Coleoptera) associated with cattle dung in Poland, Eur. J. Entomol. 101: 185-188, 2004

Odd little things

When we learn about different animals, we are usually told about the big picture, the general characteristics that will help us identify a particular group. As we study specific classes/orders/families we come across some specimens that don’t quite match those broad guidelines, and it’s always a treat when we see them live and up close instead of reading about them in books and journals.

Today I went to my university’s campus to collect some insects. I was expecting to find some beetles, flies and grasshoppers, and maybe some aquatic insects, but not much else. While rolling over a log, we found this:

Milpies enrollado 02At first glance it looked like an arthropod egg of some sort, but then it started uncurling, revealing that it was actually an adult arthropod:

Milpies enrolladoWe’re usually told as kids that woodlice are the little bugs we find that can roll up into a little ball, but this particular specimen had too many segments to be an isopod, so I thought it might be a pill millipede and got excited. I had read about them, but I had never seen one in real life. When I got back home, I took a few pictures and noticed that some things didn’t quite match: My specimen had too many body segments (pill millipedes have 13 at the most, as far as I know), and the overall shape was different. It was much more stylized and “pointy”, whereas pill millipedes are rounder, at least the ones I had seen online.

MillipedeWhen I reviewed pictures of the cephalic region, I noticed that the first and second body segments formed a particular shape, like a bicorne hat similar to the one Napoleon Bonaparte wore:

BicorneWhile odd, it makes perfect sense; the end of the body aligns with the union of the first and second segments when the millipede is curled up.

I still don’t know to which group this millipede belongs, and I welcome any input regarding an ID; I have three specimens at home in case more pictures need to be taken.

Now, finding one creature you’ve never seen before in a place you visit often is great, but seeing two in one day is remarkable. While glancing at some leaves, I saw what, from a distance, looked like a group of gregarious caterpillars:

Limacodidae 01Keep in mind that I was a few feet away, and my first thought was something I had seen before: gregarious Catasticta caterpillars, with their light colored bodies and dark heads, both covered in hairs. They tend to stay together, even different instars:

CatastictaI asked a colleague to come take a look, and she poked it with tweezers. It was then that we realized that it was just one caterpillar, and not several. We were excited to see this for the first time: it was a hag moth caterpillar (family Limacodidae). We turned it over, and there it was, definitely a single caterpillar:

Limacodidae 02These caterpillars are quite interesting; they don’t have well developed prolegs, and they move in a worm-like fashion. Now, we were looking at it and discussing the advantages of the fleshy appendages, which lead us to ask ourselves how it would roll over. Cylindrical caterpillars usually just twist their bodies along their axis 180 degrees, and that is usually enough to allow the legs to grab on to something and roll over. But this caterpillar can’t do that, since its reduced legs and dorsal appendages don’t allow for such maneuvers. So how would it turn over?

Simple: It did an assisted backflip.

The caterpillar stretched its head and front of its body backwards, until its mandibles were able to bite the leaf it was on, and then it contracted all of its ventral longitudinal muscles so that the body rolled over its head and landed right side up.

I’ve said it once and I’ll say it again: the insect world is awesome!