Will Hawkes
E N T O M O L O G Y
Day 8: A salty frog, beautiful snake and big spiders.
Today was MUCH drier and started off very well. Sat around the breakfast table fending off persistently hopeful sweat bees, we were planning the day’s cockroach experiments for our project when an interested shout came from behind me. Dave had spotted one of the strangest animals in the jungle, a predatory hammerhead flatworm. Flatworms are odd creatures, they don’t have any organ to help them breathe like we have and instead can absorb oxygen through their flat body and thin skin. They also have the unfortunate morphological characteristic of not having a complete digestive system, meaning their mouth is used for both ingestion and excretion.
Flatworms are hermaphrodites meaning that they have both male and female sexual organs During flatworm sex each individual will role play as either male or female with the female carrying the young. However, if a flatworm cannot find a partner it can just fertilise itself to produce eggs.
Amazingly, these animals can actually also reproduce asexually via fission – splitting in half and regenerating the missing parts!! This ability to regrow also has the advantage of protecting the worms from death by injury.
A Bipalium species of predatory flatworm.
This beautiful Bipalium species of hammerhead flatworm Dave found needs damp conditions to live and slides about on closely packed hairs called cilia which make up its creeping sole. The flatworm slides about on the hunt for its main prey: earthworms (the flatworm is unfussy though and will be cannibalistic if the opportunity arises). Earthworms are located by the flatworm using receptors under its head that detect chemical cues given off by the prey.
Once found, the flatworm leaves a sticky slime trap that ensnares the earthworm. The flatworm wraps itself around its prey and, when in position, reverses its throat into the unfortunate worm! The flatworm then secretes enzymes onto the earthworm, digesting it externally before sucking up the processed meal.
A Bipalium species of predatory flatworm.
The next few hours were spent watching our cockroaches try and decide what rock colour to shelter under. We will be working on this project tomorrow too and so I will detail more then.
Beetle hunting was the plan for the rest of the afternoon. Found first was a middle sized chafer beetle in the genus Exopholis. These beetles like to eat the leaves of the large Dipterocarp trees which populate the jungle. The young, however, are much more destructive and enjoy munching their way through the roots of trees including those which have a commercial value such as rubber and tea. He was found in the tarpaulin of the shelter and must have been attracted to the lights last night. Quite a round beetle he seemed quite unsteady when I put him on a log to be photographed! Like all beetles, he plays an important role in the forest’s food chain. Many larger animals like birds, mammals and reptiles would gladly eat him. However, he also fills an important part of the diet for some local people. When his species is especially plentiful they are collected at light traps and fried or boiled. Apparently they are quite delicious, although I was still full from lunch, so he was left to go on his way.
An Exopholis species of chafer beetle.
The next beetle was a beautiful animal, Eulichas fasciolata – the chequered forest stream beetle. Superficially, it looks quite similar to the click beetles (Elateridae) we found a few days ago (Day 6) with its expanded head/thorax region but is in fact an entirely different family, the Eulichadidae. The young of the Eulichas genus interestingly are strictly aquatic which is quite unusual amongst terrestrial beetles. The larvae live in the sandy substrate of clean forest streams and will feed on rotting detritus and sometimes roots as well. The adults, on the other hand, are strictly terrestrial and tend to live close to the streams on neighbouring vegetation. This specific beetle, Eulichas fasciolata, is found nowhere other than Borneo and, according to my book, our finding was the first for the Kalimantan region!
Eulichas fasciolata - chequered forest stream beetle.
As night fell I found a beetle whose life history was needed for the beetle video we were working on, a dung beetle. The beetle in question was one of the Paragymnopleurus species and was a dung roller! Crucial for forest ecosystems, she finds the dung of a larger animal using her sensitive smell receptors and moulds it into a ball before using their longer back legs to roll the dung backwards into her chamber. Here she will either eat it herself or use it to feed her young. Interestingly, if she is feeding her young the ball of dung is far neater than if she is just feeding herself!
Because she buries the dung underground, the nutrient recycling of the jungle ecosystem is sped up: The dung is now in closer proximity to roots and other animals that play a role in decomposition such as earthworms.
A Paragymnopleurus species of dung beetle.
By now it was tea time and I was being called back to camp. Wolfing down the food, Ted and I were extremely anxious to get out on a night walk – in no small part because of Ted’s finding last night that I could barely wait to see, hoping against hope it was still there!
Not many people came with us on the walk wanting an early night instead and so just Kelly, the three Indonesian students (Blenda, Desintha and Dhani) plus Ted and I set off with our guide up the river. Our first find was a middle sized frog sitting on the bank with a ridged back. Closer inspection by Ted revealed this as a crab-eating frog – Fejevarya cancrivora. (It’s genus name does not sound very ‘latin’ because it was described by a Hungarian - István József Bolkay!) This frog has the amazing title of being the only frog in the world that can tolerate brief periods in seawater – where its tadpoles can develop too!! It needs this adaptation because it also lives in mangroves eating crabs. Crabs probably don’t form a huge part of its diet here as insects are more plentiful but I’m sure it would still eat the freshwater crabs about (see day 5).
The crab-eating frog - Fejevarya cancrivora.
Another couple of Cosmodela aurulenta tiger beetles were sat on the leaves overhanging the river. Night is definitely the best time to photograph these animals as they are so quick during the day. This one is showing off its beautiful rainbow legs!
Cosmodela aurulenta tiger beetle.
Glancing down at the pebble beaches revealed something that fills many people’s nightmares; a Scutigera species of centipede – something not even Ted is that keen on! I quite like their excessive number of legs however. And the fact that they seem to glide over the floor in an almost serene manner if it wasn’t for the rapid speed that they travel! The centipede’s legs (especially the longer hind ones) can be dropped easily if attacked by a predator to aid escape. Although I am not sure why a predator would want to attack one of these animals, they are actually quite dangerous with a highly venomous bite. But just like most creatures, if you’re careful and let it do what it wants then it won’t pose any threat
A very leggy Scutigera species of centipede.
Almost under my boot was a juvenile river toad, perfectly blended in with the pebbly beach. This supposed background colour matching of frogs was studied by some friends in another group. Juveniles especially would be a good meal for many different forest predators and so being able to hide effectively is an excellent survival strategy.
A camouflaged juvenile river toad.
Some of the larger spiders would happily take that small toad as a meal and I found the largest swimming huntsman (Heteropoda natans) of the whole trip on a rock near the bank. This massive female must have been easily 25cm in legspan. As seen on day 4 these spiders are very at home near the water; they are light enough to run across the surface on specialised hairs and can even hide under the surface if under threat! A beautiful Dolomedes raft spider was also seen, it was the same (or a very similar) species that I found eating a frog back in our first location – the Sungai Wain forest (write up imminent!).
Dolomedes sp. of raft spider.
A very large swimming huntsman - Heteropoda natans.
Leaving the river in the valley below, we began to scramble up the steep path barely searching for animals because at the top of the hill was hopefully the creature Ted was so excited about last night. Pushing through leafy branches we rounded a corner and there, coiled in a bush amongst large jungle leaves, sat the animal we had hoped for – a Bornean keeled pit viper.
The absolutely beautiful bornean keeled pit viper.
Around 50cm long this was likely a juvenile or adult male. A white tipped tail followed a brief area of brown which turned into the snake’s winding green body. Small red/white spots dotted scales, his underside was slightly paler with staggered dots of the same colours leading to a characteristically triangular head. A red and white stripe separated the snake’s dark green upper head from the paler lower, surrounding cat-like yellow eyes. Just in front of these eyes is the pit that gives this group of snakes its name. He has two pits, one on each side of his head, and they are the openings to extremely sensitive infrared receptors. He can use these pits to find the unfortunate prey animal from its body heat. By having two pits he may even be able to tell the direction and distance he is from the prey, an excellent adaptation for hunting at night! These snakes are arboreal and feed primarily on rodents and birds. They will stay in one good hunting spot for days at a time (which is why we were hopeful of re-finding it), waiting to ambush passing prey, perfectly camouflaged during the day time. This particular snake was also quite calm about the big lumbering human hanging onto a nearby tree to try and get some photos. He was quite curious as you can see by him tasting my scent with his tongue. He does have quite exciting venom so we made sure not to disturb him too much and we headed off before long, following the call of the elusive Greater Frogmouth bird.
Tasting the air to wonder what I am.
His very triangular head.
His two infrared sensing pits and glaring eyes.
Ted crashed off down the jungle, headtorch on full beam in the hope of catching a glimpse of this bird which had taunted us since Sungai Wain. I hung back, distracted by a jungle earwig. Longer and thinner than our UK species with much thicker legs but still very much an earwig.
A species of Bornean earwig.
Suddenly I caught some eyeshine in my torch’s beam on the forest floor. Creeping closer the largest male Orange huntsman (an undescribed Heteropoda species) I had seen was sat on the leaf litter. With a 20cm leg span he is separated from his female counterpart by his shiny white patches on his legs. While his long legs do allow a chase-down approach to hunting, this spider is far more likely to sit and wait at the edge of a trail and prey on passing traffic. Females are slightly larger and more orange and just as pretty. I think this is my favourite huntsman from the trip.
A male orange huntsman (Heteropoda sp.) note his white legs.
The stare of an orange huntsman.
Heading back towards camp, immensely pleased with success of our night walk, we happened upon such a strange animal sat on a tree trunk. An orange-tipped lantern bug – Pyrops intricta, possibly the adult of some of the nymphs we found yesterday (day 7)! Despite its name this bug does not give off any sort of light and uses its impressive ‘nose’ (which is actually its rostrum (mouth)) to suck up sweet sap and fruit juice from trees. Interestingly, some moths have learnt to drink this bug’s urine as it is very sweet and so a good source of sugar! We saw a couple of different species on the trip but this was the only sort we found in the Tane’Olen forest. With its blue nose, orange head and yellow spotted green wings melting into red/brown tips, this is one of the most stunning insects in the jungle.
Pyrops intricata - Orange-tipped lantern bug.
Traipsing back into camp with big smiles, we shared the night’s events with some vaguely envious campmates who were still up. Climbing into bed, determined to make the most of our final day in the jungle tomorrow, we fell asleep listening to the decidedly goading calls of the horned frog – a species that still evaded us.