Caterpillar of the day: Xylophanes [germen?]

In the Cacao Sector of the ACG today I finally saw my first early-instar Xylophanes sp. caterpillar (I think Xylophanes germen). Green with mostly yellow eyespots! I hope to see more, but apparently they are more frequently observed here in May and June. One of the parataxonomists at Cacao told me that there are roughly 7-8 species of Xylophanes in the Cacao Sector alone!

Xylophanes sp. (Sphingidae)

I was excited to see yet another bag labelled "Sphingidae", but unfortunately for me (and the caterpillar) it had been parasitized:

You can even see the classic Sphingidae 'horn' in what is left of the deflated caterpillar body. An even better photo is below. This is a parasitized Xylophanes cthulhu caterpillar that I came across on the ACG caterpillar database - you can even see the eyespots still!

It almost looks like the paracitoid cocoon is dressed as a ghost for Halloween doesn't it? If the caterpillar that I observed today really is Xylophanes germen, it would be great to see this guy in its later instars - they are pretty intense.

Xylophanes germen (Sphingidae)

Photos below from the ACG caterpillar database

Ultimate instar:

[relatively drab] Adult:

Caterpillar of the Day: Neococytius [cluentius?]

This caterpillar was observed at the San Gerardo Station in the ACG. I saw this individual twice, so I have photos from both the pre-penultimate and ultimate instars. Another giant Sphingidae. This specimen thrashed its anterior half quite violently when it was pinched with forceps (especially on Aug 26). In the late instars these guys get to be >100 mm long.

Neococytius [cluentius?] (Sphingidae) Aug 15 2011 - Pre-penultimate instar

Neococytius [cluentius?] (Sphingidae) Aug 26 2011 - Ultimate instar

Neococytius [cluentius?] (Sphingidae) Aug 26 2011 - Ultimate instar 

Neococytius [cluentius?] (Sphingidae) Aug 26 2011 - Ultimate instar 

It seems like the white could make these guys blend in to the foliage by resembling the streaks of sunlight that pass through the canopy. Many predators use edge detection to recognise prey items, so this colour pattern could also help break up the outline of the caterpillar when it is sitting on a leaf.

The pupa is a typical looking for a Sphingidae (photo from the ACG database):

This caterpillar will eventually grow up to look like this (photo from Wikipedia.org):

Just another great example of a species where the caterpillar is more beautiful than the adult!

Continuing on the theme of masquerade...

As promised here are some photos of that caterpillar that was peeking out in one of the photos in my last post. This is another Prepona sp. but I'm not sure which. I only found it because of the conspicuous frass pile collecting on a leaf underneath. What drew me to that tree though was the characteristic feeding damage from Prepona caterpillars. They chew off the first half of the leaf but leave the middle vein, then to that vein they silk small cut trimmings of that leaf to give it a "trashy" kind of look. During the smaller instars the caterpillars are usually seen dangling from the end of the vein in full sight, but they look so much like the other "trash" that you often miss them. The bigger ones will sit right on top of leaves or on branches. This one was dangling from a full dead leaf that had been silked to the branch. It was wrapped kind of in a spiral shape on that handing leaf. I showed it to several people and they didn’t see it even when they were inches away.

Prepona sp. (Nymphalidae)

Here is a smaller individual from the same plant (maybe a full sib). The first photo below shows the characteristic feeding damage.

It almost disappears once it gets amongst its "trash" on the leaf vein. In many ways masquerade is more similar to mimicry than crypsis. When people discuss crypsis as an anti-predator defence they usually mean that the predator does not detect the prey. It is perhaps more realistic to recognise that the predator does see the object it just doesn't think that that object is a meal. In classical Batesian mimicry theory, the number of mimics should be smaller than the number of models (model = the object being mimicked), otherwise predators don’t learn to avoid that type of prey. Biologists call this "frequency-dependence" because the efficacy of the defence depends on the relative frequency of the models to mimics. In theory this should be the case in masquerade too, it's just that the model is usually something incredibly common like a living/dead leaf or a twig.

On a night walk tonight I found another dead leaf mimic:

A colleague/friend recently blogged about The weird and wonderful world of katydids. I doubt that I could do a better job of enthusiastically describing these guys so I'll leave you to read his post. He writes very well and I highly recommend following his blog: Katatrepsis. He's right though, the detail of the false venation is mind-blowing.

Non-caterpillars and coincidental eyespots

I set out today looking for caterpillars in the forest here in Santa Rosa (ACG). Finding caterpillars is no easy task, but can be fun and very rewarding when you do have a good find. Caterpillars get hammered by predators so it pays to be highly cryptic. Even when you know where and when to look, it can be very difficult. The parataxonomists in the park here consistently blow people like myself away with their trained eyes scanning the foliage.

Many caterpillars employ a "masquerade" strategy, looking like various inedible items in their habitats. Here in the tropics dead leaves are a common model. To give you a sense of why this might is the case, here are a set of caterpillar-like objects that I saw today in the forest.

One of the above photos actually does have a caterpillar hiding in it. Scroll up and see if you can find it!

Hint: the caterpillar’s frass (caterpillar poo) gives it away.

You can see the little head peeking out from the top right of the hanging dead leaf in the last photo. Actually, I found 3 different individuals on the same plant, presumably all the same species of the Prepona genus (Nymphalidae). I think these are a different species from the 2 other Prepona species I have encountered here at the ACG. I will post some shots of these new guys tomorrow.

Another thing that I observed was several paired circles in the forest that were totally innocuous. Here are a few examples:

OK, I'll admit that it is a bit of a stretch to say those look like eyes. The point I'm trying to make is that there are (implicitly) other cues involved. One of the arguments used to support the idea that eyespots are mimicking eyes is that when animals see objects that even vaguely look like eyes it usually indicates a threat. Immediate retreat from anything that looks remotely eye-like should be a must for these attackers (e.g., small birds), or else they risk death (e.g., an attack from a snake). But fleeing from everything that looks remotely eye-like must also entail a cost, either energetic (quick retreat should have some energetic cost) or opportunistic (missing out on a big meal). Obviously other cues in addition to the eyespots are critical to initiate a retreat from an attacker; things like hostile behaviour that resembles an attacking or dangerous snake.

Caterpillar of the day: Morpho sp.

So far I have come across 2 caterpillar specimens of what I just found out are Morpho sp. Morphos are one of the world’s most beautiful creatures. The top of their forewings are a truly dazzling iridescent blue. In addition they are quite large butterflies (species range from 7.5 cm to 20 cm wingspan) so you can see them from great distances. They have a reputation for being notoriously difficult to catch. Henry Walter Bates even remarks on the difficulty of catching Morphos in his book: The Naturalist on the River Amazons. Here is a photo of an adult in a collection:

Morpho helenor hector (Nymphalidae)

I see a Morpho almost every day here, but it is very difficult to get a good photo, because they are always moving. When they land they keep their wings closed and stay very still. Here is a photo of a Morpho that I took earlier this trip:

Morpho sp. (Nymphalidae)

Yup, those are eyespots! These ones have been harder for biologists to explain because they are constantly displayed and not really paired in the way you might expect eye-like markings to be. The caterpillars have an odd colouration too. Below are two specimens that are yet to identified down to species.

This one is from San Gerardo Station:

And this one is from La Perla Station:

Very similar looking specimens but you can see differences in the colour pattern if you look closely.

Clicking Warrior Butterflies!

Today I visited a new Sector of the ACG - Munde Nuevo. After driving some severely eroded roads and crossing though a stream we arrived at the La Perla Station. I was able to get measurements from 22 individual caterpillars, so a good haul. At lunch though I took a walk around and watched some of the adult butterflies. After being briefly distracted by a few White-throated Magpie-Jays I heard an odd clicking sound. Looking around I eventually realized that it was coming from pairs of butterflies.

Many butterflies are territorial. Males defend these territories by chasing out intruding males. They are sometimes seen engaging in a spiralling flight where eventually one male gives up and leaves (usually the intruder). Many species here in Costa Rica are territorial and I enjoy watching them defend their areas and trying to mentally figure out where one territory ends and the another begins.

I only saw the clicking expressed during these spiral flights, so I suspected that it had something to do with territoriality. I was told today that the clicking butterfly I observed was from the Hamadryas genus- the so-called Cracker butterflies. They primarily eat fermenting fruit. The Wikipedia article details the behavioural ecology pretty well so you can read more about that really interesting work there: http://en.wikipedia.org/wiki/Cracker_butterfly#Behavior

Hamadryas sp. (Nymphalidae)

Apparently these guys are becoming less common around Santa Rosa. This is partly attributed to the progressive loss of host plants resulting from natural succession of the forest here (much of the ACG forest is secondary growth). La Perla is in an earlier successional stage, and it is at a higher elevation, so it is thought that this is an example of a mobile species sliding up mountain sides with climate change.

Lanturn Fly (Fulgora lanternaria)

I know this is supposed to be a blog about caterpillar eyespots, but I couldn't resist posting these photos. This lantern fly flew over to where I was sitting one night and when we picked it up to take a closer look it displayed its eyespots quite aggressively.

Fulgora lanternaria (Fulgoridae)

The strange look of this species has sparked many stories and folklore; it is sometimes called "machaca" here. Their common name comes from the false belief that the structure on their head lights up like a lantern. This was apparently believed by the authority at the time, Maria Sibylla Merian, and picked up by Carl Linnaeus. This is where the specific name (i.e., the species name) laternaria came from. Other species in this genus include phosphorea and candelaria also as a result of this belief.

I have heard that this peanut-shaped protuberance is sometimes drummed against a tree, possibly as a form of communication. This would make sense because that part of the head is hollow and could be a kind of resonance chamber to deepen the drum beats, helping sound travel further into the forest. It has also been suggested that the head could be a way to intimidate attackers (it is also called an "alligator bug") by making the insect look bigger and bitey. There is a legend here that if you get "bitten" by a lantern fly you need to make love in the next 24h or you will die! After we let it go it started flying around again and when it landed on the crotch of my pants one of the other researchers here joked that I should "Watch where it bites now!" - we all had a good laugh. Actually, they are a type of planthopper and can't really bite you because they have long piercing-sucking mouthparts made for feeding on plant juices.

Automeris zugana PWND!!!!!!!!!!1

I came acorss these images of a tailless whip scorpion eating an adult Automeris zugana on the ACG photo database. As far as I know this photo was not a staged event, and the fact that it was in the ACG database suggests that it is in fact a natural predation event. The caption for these photos reads:

"Amblypigidae that has just caught this male who came to the lights in the house"



I think this demonstrates an important point: eyespots are effective against some predators and not others. Although this may largely go without saying, it is critical to keep in mind. Birds and monkeys are probably the main predators of caterpillars and moths, but parasitic flies and wasps are also important enemies of caterpillars and I'm not sure that they would be deterred by eyespots. Obviously this Amblypigidae wasn't.

See also a related earlier post: http://caterpillar-eyespots.blogspot.com/2011/07/some-eyespot-humor.html

Caterpillar of the day: Caligo atreus

Caligo atreus (Nymphalidae)

I observed this species when I was at the San Gerardo station in the ACG. Until this one I had never seen anything like it. This specimen was a 6 cm long pre-ultimate instar. 

Late instar Caligo atreus caterpillar

Late instar Caligo atreus caterpillar

Late instar Caligo atreus caterpillar

The head almost looks like a tribal mask doesn't it? The caterpillar body seems to match the leaf of its host plant fairly well. I suspect that it uses those menacing-looking spines on its head as a club to swing towards attackers when it is harassed. But, the most interesting part of this species is its pupa. I would love to see the pupa of this species becasue it may be protected by a form of snake mimicry too. Here are some photos of the pupa from the ACG caterpillar database:

Close up of Caligo atreus chrysalis. Photo: ACG caterpillar archive 

Caligo atreus chrysalis, side view  Photo: ACG caterpillar archive 

Caligo atreus chrysalis, dorsal view. Photo: ACG caterpillar archive 

The pupa of this species can be over 5 cm long! The pupa's shape does resemble the head of a viper, and the white spots are roughly in the right place if they were mimicking snake eyes. But could just a head be enough to intimidate predators from attacking? Probably, especially if attackers do innately avoid things that looks like a dangerous snake. Further, the head and eyes are probably the most salient cues used by other animals to indicate that they are dealing with a threat. If the little spots don't increase the pupa's conspicuousness much and ward off attackers even part of the time then it is at least conceivable that these spots evolved as a form of eye mimicry.

Most of the other instars look like my photos above, but as in many species the ultimate instar has darker colouration. Here is a photo again from the ACG caterpillar archive:

Photo: ACG caterpillar archive

Caterpillar of the day: Automeris sp.

At the end of an exciting day of photographing several examples of the snake mimic Prepona sp. at the Cacao station the parataxonomists returned from their day-long collecting trip with some fresh specimens. Among them was this beautiful Saturniidae caterpillar. I think that it is from the Automeris genus which contains several very similar looking species, although I can't be sure.

Automeris sp. (Saturniidae)

This is by far the most beautiful caterpillar I have seen so far here at the ACG, but its not like this caterpillar needs a "Do Not Touch" sign - there is just something nasty about the look of those spines. Many caterpillars of this genus lay multiple eggs on the same host plant, which seems to be the habit of many butterfly and moth species with aposematic caterpillars. Unfortunately, when one of the parataxonomists was collecting this specimen she accidently touched another with her forearm. The area of her arm near where she touched the caterpillar was swollen and looked painful. The sting of some caterpillars can be extremely painful and occasionally fatal so caterpillars with spines should always be handled with care. Some caterpillars have urticating hair that can be similarly painful or irritating.

Update: I met with the parataxonomist later and she told me that it didn't hurt that much and felt hot - more like a burn. After a day the swelling went down and the mark was gone shortly after that. The pain caused by other species can be much more extreme, so generally heed the animal's warning and stay away.

Caterpillar of the day: Xylophanes sp.

There is a genus of Sphingidae moths that where eyespots are particularly common: Xylophanes. Many of the species here have just the pair of eyespots on the anterior body segments behind the caterpillars true head. I have only seen 2 specimens so far from this genus - 2 different species I think. The first one had already reached its pre-pupal stage and the other was an ultimate instar (just before the pre-pupal stage).

Xylophanes sp. 1 (Prepupal)

Xylophanes libya

Xylophanes libya

You can see the caterpillars real head better in the second photo- it is slightly curled under the body segments. This prepupal stage sometimes found inside leaves that it had previously attached together as a shelter. They rest in a "C" shape, and when they are lightly pinched or touched in this pre-pupal stage they will flick to an inverted "C", perhaps wiggling in a snake-like way.

The other specimen I saw in Cacao was in its ultimate instar:

Xylophanes sp. 2 (Ultimate Instar)

These eyespots are not overly conspicuous, but probably were in an earlier instar. Once I get a better ID I will try to post shots of the earlier instars for comparison. I have seen caterpillars from this genus pull their head in which helps make the body segments with the spots larger (also making the spots larger) and creates a snake-like head shape (at least to the human observer). I was told that some large caterpillars also do a wiggle behaviour when held which apparently feels like a snake.

Finally, here is a photo of Xylophanes anubus from the ACG caterpillar database. This is in its pre-ultimate instar. Again, many of these species are green at this point and trun brown only as they reach their ultimate instar. My guess is that this colour change has to do with microhabitat use. The earlier green stage probably spends most of its time on or amongst the leaves feeding, while the later brown stage may spend time looking for a good place to pupate. Both green and brown snakes could spell danger for an unlucky bird so both may be effective deterrents. The eyespots do however seem to be more highly contrasting on earlier green instar.

Xylophanes caterpillar. Pre-ultimate instar. Photo: ACG caterpillar database