Crab cannibalism

 There's simply no hiding it - crabs are among my favourite foods. And of course, I am not alone. Kingfishers, storks, cranes, otters, and a number of wild species eat crabs regularly.

As some of us observed, apparently crabs are fond of crabs too. In this blog I showcase an observation made in the peaceful sacred grove of Kukdeshwar in Udaipur district. With a perennial stream that is protected thanks to the local deity, this spot in the Aravalli mountains is verdant even in the summer heat. Our friend, Dr. Anil Sarsavan - an extraordinary naturalist - showed us the magic of the grove. The wet part was lush, and hopping and buzzing with life.

 

As we climbed on away from the stream, the dryness was stark, but the beauty of the dry trees alongside the evergreen ones alongside the bright blue sky dappled with clouds was breathtaking. 

Ok, back to crabs and our observation. Freshwater crabs in Indian streams and rivers have been poorly studied and even their taxonomy is just being worked out. The large crabs in Udaipur's streams were kindly identified by the taxonomist Dr. Sameer Pati using the photographs I uploaded on the portal inaturalist.org. One of these chunky chaps is apparently the Brown Freshwater Crab Barytelphusa cunicularis. These are fairly common in streams, and venture out on brief sojourns onto the forest floor in search of food. 

Their coloration makes them hard to see on the dry leaves in the dim forest light. A startled crab puts on an aggressive display - one that I am always content to watch from afar. Those pincers be stroooong!

The ones in the stream are difficult to spot as well, being similarly coloured as the sand-and-stone of the Aravalli mountains. A hub-bub in one stream caught our eye one morning, and we saw two large crabs feuding. One chap moved faster and had the other chap in his claw moving so rapidly that we barely realized it had happened. Claw crunched through crab-shell in a jiffy. It vanquished literally crumpled.

 

The victor dragged the unmoving crab to beside a large rock and began feeding. The flowing waters of the stream turned slightly milky - ostensibly from liquids inside the crab being eaten. The "blood" was whitish? The harvested blue blood of the marine horseshoe crabs is famous, but I had no idea that the primary colour of the innard-fluid of a freshwater crab was white. 

The victor then crushed the shell completely, and a bright white fluid gushed out colouring the clear, flowing stream. Other crabs did not appear to be attracted to the flowing white stuff, and the meal was had in peace.

We watched mesmerized as claws reached into the broken shell and pulled out succulent white flesh to chew as white fluid continued to pour out and quickly washed away. As the meat was consumed, it took only a few seconds for the water to become clear again leaving no trace of the violence that had just occurred.

There is a considerable amount of research on cannibalism among freshwater crabs, but these studies focus on adult crabs eating freshly hatched or slightly grown young crabs. Given the aquaculture importance of some freshwater crab species, cannibalism is a serious matter for farmers of these species. 

Not surprisingly, there appears to be rather little written about cannibalism of adult wild freshwater crabs. In one experimental study, larger freshwater crabs preferred to cannibalize much smaller crabs, males were more cannibalistic than females, and cannibalism disappeared when alternative foods were offered. Crab species have been observed to increase cannibalism during molting when molting crabs display a high degree of agitation making it easy to spot. Aquaculture farmers appear to be familiar with this behavior and routinely provide refuges to reduce cannibalism. Had we observed a molting Barytelphusa cunicularis being cannibalized?

I wonder also if much of the cannibalistic action takes place in the shelter of darkness during the night making it appear that this is rare. Maybe the younger, smaller crabs are just too agile for the biggies to catch, and seem to be able to escape by running away on rocks. Lots of questions, and far too few answers. The way it will always be!

(Photographs taken 30 April 2023. Thanks muchly to Dr. Anil Sarsavan for showing Swati and I the lovely Kukdeshwar sacred grove in Udaipur district.)

Beetles with spines

 The diversity of form and shapes of beetles are perhaps unparalleled in the animal kingdom. There was clearly an inordinate need for this variety, and I am growing rather fond of discovering more of these. This blog shows a few that I found in the Vaccine Depot Ground of Belgaum city.

The Vaccine Depot Ground in Belgaum city, south India seems like just another green urban space, but a closer look helps reveal it to be a magnificent remnant old forest. The human touch, however, is everywhere - buildings, rows of one tree species, a block filled with an exotic tree, invaluable open grasslands being destroyed by feel-goody tree plantings, and of course a growing network of paved paths. For the burgeoning Belgaum city, the depot's greenness provides critical functions of being both a vital lung and giving people a peaceful natural experience during their morning walks. 

A large manner of wild species use the depot and one group that has caught my attention is rather wacky. These are beetles with spines. Not vertebrae, of course, but actual sharp, long, curved and varied spines. Entomologists know of these and plenty has been written about their taxonomy, role in ecology, and so on. Quite a few different kinds of spiny beetles occur, and here are a few from Vaccine Depot. Here, I share my amazement at the crazy-coolness of a few beetles I found at the Vaccine Depot Ground.

The first one I saw was a weevil, Hoplapoderus gemmatus, that was tiny but packed a punch in appearance. This species belongs to a group broadly named as the leaf-rolling beetles, or Attelabidae. Seen from above, the beetle is good looking already sporting an exotic gold-and-black appearance.

The spines, however, pop when this fella is viewed slightly from the side. Spines of this beetle are somewhat gentle, as if included as an afterthought. And they add, I thought, quite a surprising attractive complexity to the look. 

A much tinier, but far spinier, beetle I saw was Hispa ramosa. This chap was about as thick as a grass blade and looked more like a tiny caterpillar thanks to the densely covered spines. Hispa belongs to a group of beetles called "leaf beetles" - a group that has quite a few species whose larvae feed on leaves of both wild plants and on domestic crops. 

The bizarreness and fabulousness of the spikiness went up a few notches with two Tortoise and Hispine Beetles. One that I have not yet been able to identify to genus or species level is this gorgeous chap sporting a row of two-pronged gold-and-black spikes on its thorax. These were completely overshadowed by the forest of black curved spines on its wings! Look closely and you can see a row of golden spikes jutting out from its sides.

Hate it or love it, the chap is arresting. Add the velvety looking flat feet at the end of the yellow legs, and we have a certified looker in our hands.

   Then came this astounding spined beetle that managed to beat our looker above - Platypria, another leaf beetle. It was by accident that I found this beetle. It was in the web of a social spider quite dead but affording a great opportunity to take photographs from all sides. Four species of this genus are known from India, and going by the photographs of all the species, I would venture to guess that I had found P. echidna.

There were multi-colour spines everywhere on this beetle. And in all sorts of shapes. I assume that the generic name alludes to its overall shape somewhat resembling a Platypus. While the back had several simple spines, the sides were awash with spine diversity. Six-pronged ones, three-pronged ones, coloured ones, semi-transparent ones - you name it, he had it! Add the lush golden-yellow legs and I had meself an unbelievable beetle!

Spines and spikes on beetles have attracted some research attention, and are known to reduce predation. Not only are these spined beetles avoided by birds and frogs and lizards, but also by parasitic wasps. The spines clearly lost their use when caught in a web. It would have been really great to watch the spiders and see how they avoided all of those spines. Perhaps I will get lucky another time.

(Photographs were taken in the Vaccine Depot Grounds of Belgaum, Karnataka during May 2024.)

A predator becomes prey

 Spiders are deadly predators. They use a variety of methods to catch their prey. The ones sitting on their webs waiting for something to be caught in the sticky web are the most well known. This gigantic Nephila pilipes, or the Northern Golden Orb Weaver is one such sit-and-wait species that builds large webs. Other species and tiny males of the species are parasitic on the webs of the large females, eating up prey that the female bundles up in a web and stores for future feeding.

Also a sit-and-wait predator, this Hersilia, or the Two-tail Spider, dispenses with building a web. It is superbly well camouflaged on the bark of trees where it waits for prey sitting upside-down. As an insect or another prey wanders by, the spider spins a web around it by running round and round the prey until it is unable to move. The spider then, as seen in the photo below, moves in and bites the prey injecting it with a poison that incapacitates it. The poison also dissolves the innards of the prey allowing the spider to suck out the juices at leisure.

Then there are the wandering spiders that roam around looking for prey, like this handsome Plexippus paykulli, also called the Pantropical Jumping Spider - a species commonly seen in gardens and homes.  

One sit-and-wait spider that is incredibly attractive is the group collectively called the Crab Spiders because of their overall appearance. These spiders come in a variety of colours matching flowers on which they sit awaiting insects that come for nectary and pollen. Several of these Crab Spiders lived on the Rangoon Creeper vine-gone-wild Swati and I grew in our tiny garden in Udaipur. 

One evening, we noticed struggling movement on one of the buds. It was a black-and-white hoverfly that appeared to be floating in the bunch of flowers. Hoverflies are also called Flower Flies and adults feed on nectar and pollen of flowers. A ghostly form skulked behind the struggling fly. It was a lovely white-and-pink Crab Spider that had successfully caught itself a large meal.

The spider was surprisingly small given the size of the hoverfly it had grabbed and vanquished. The struggling of the fly died down and the spider proceeded to bite into its belly and began feeding. After several minutes, we watched the limp and empty body of the hoverfly drop from the flowers as the Crab Spider let go after having its fill. The spider then proceeded to clean itself before again positioning itself below a new flower.

 
We had barely begun admiring the Crab Spider's skills when there was a very rapid jumping movement towards the Crab Spider. Before it could move, it was in the jaws of a new predator that had been quietly roaming around, perhaps even watching the drama that had unfolded. The new predator was a species of jumping spider quite royally named Thyene imperialis.

Despite being smaller than the Crab Spider, the bite of the Thyene imperialis appeared to have an almost instant effect. The Crab Spider appeared to crumple and was taken around quite effortlessly by the new predator. Thyene positioned itself to get away from our prying eyes and even dangled the Crab Spider over leaves as it jumped away with its fresh food. 

Thyene imperialis is reputed to be a very effective predator, even jumping into webs to grab spiders waiting for prey. The Crab Spider really had no chance once it had been spotted. Even the most well camouflaged and careful of predators can become prey in a trice.

The variety of spider species and behaviours is rather vast. I have no doubt that there will be other blog posts on these eight-legged wonders.

(Photographs' location and dates:

Nephila pinipes: 12 Jan 2024, Goa.

Hersilia: 15 May 2024, Vaccine Depot Grounds, Belgaum.

Plexippus paykulli: 08 September 2023, Tilakwadi, Belgaum.

Crab Spider and Thyene imperialis: 04 December 2022, Govardhan Vilas, Udaipur.)

Damselflies sometimes carry water mites

 Damselflies are less famous than their relatives, the dragonflies. They are far more delicate in appearance, much smaller, and mostly fold their wings when resting making it more difficult to spot them. 

Like dragonflies, the damselflies are mostly found near water (rivers, ponds, lakes), but some species are also found readily in gardens - especially gardens that have unkempt lawns with abundant grass.

Swati and I kept such an unkempt garden in our Udaipur home and were often visited by the Three-striped Blue Dart, Pseudagrion decorum, damselfly. One of these individuals carried a load on its side!

On the side of the thorax was a dark clump - a group of water mites. When viewed from above, it became obvious that this particular damselfly was a mite-favourite. There were quite a few mites on both sies of the thorax.

    The additional load did not appear to impact the damselfly in any obvious way. It flitted about catching mosquitoes and other small insects. A week later, a damselfly in the garden (the same one as before?) also had water mites, but only a couple of them. The mites had apparently jumped off and may have used the damselfly to disperse. This method of dispersal where one species uses another is termed "phoresy". Fewer mites or not, the damselfly was busy chomping all the mosquitoes it could catch!

Between 2017 and 2023, we saw only three damselflies in our garden with mites, out of several dozen observations of damselflies. The third damselfly was also seen within a week of the other two - all in October 2022. The rains had been unusually worse for a month that is normally a post-monsoon month with very little rain. Were the mites a consequence of increased rains? 

Like with most wildlife species, there is little ecological work conducted on damselflies in India. However, there is considerable work conducted elsewhere on water mites and damselflies, and these provide some interesting findings. 

• Mark Forbes and Robert Baker found that smaller and lighter damselflies carried many more mites. It may be that weaker individuals were more susceptible.
• Leung and others found that mites latched on to damselflies closer to emergence - they were clearly watching and waiting!
• Andres and Cordero's cool study found that while mites did not affect damselfly survival, heavily-parasitized male damselflies mated much less than damselflies with fewer mites. 
• Nagei and others noticed that the water mites were sort of good at escaping when their damselfly hosts were being eaten by dragonflies. Semi-engorged mites were all eaten up - clearly too busy feeding themselves. However, half of the fully engorged mites managed to drop off in time to escape being eaten. The little chaps were clearly great at survival, but only after they had had their fill! 

It was fairly yucky to view the parasitic mites close up. But the research work being done on them showed the mite-damselfly interactions to be rather cool. Now we are wondering how many damselfly species in India carry water mites, and why 2022 was such a good year for the mites in Udaipur.

 (All photographs were taken between 11 and 22 October 2022 in Arihant Greens, Uddaipur.) 

Ground orchids: Discovering the Nervillia aragoan (or concolor)

 Among the most memorable times in Udaipur for Swati and I were the weekend trips we undertook with Dr. Anil and Dr. Satish Sharma. These trips covered protected forests, grasslands, sacred groves, streams within the Aravalli valleys, and community conserved areas. 

A perk of such trips was the deep knowledge both individuals had of the plants of the region. One of these trips was exclusively to see if the Tall Shield Orchid Nervillia aragoan had flowered.

The Aravalli mountains are a tough sell for most plants, let alone tubers that need some soil. Most areas have shallow soils, but this is adequate for the ground orchid Dr. Satish wanted to show us. It had been drizzling on and off for a few days, and conditions, we were told, were perfect for the orchid to emerge. 

After a long drive from Udaipur city, we stopped beside a grove of trees. Dr. Satish led us to the shade of of these tall trees where he knew these orchids lay buried. As we approached the slope, his face burst into a beaming smile. The orchid flowers were bobbing in the gentle breeze that had caught up with us.

Green flowers were not what I was expecting, but the grace and delicacy the colouration brought to the orchids were nothing short of spectacular. The stems were short and held half a dozen or so flowers each. From the front, the "orchid" nature of the flowers became obvious.

The tinge of purple around the rim was magnificent. Some bees roamed around the flowers, but we could not see any obvious ones that were pollinators of these flowers during our short stay.

However, the pollinators had been doing their job. Green fruits and riper fruits hung on some of the stalks telling of orchids that had flowered earlier than our visit.

Like in many ground orchids, the leaves of Nervillia aragoana emerge after the fruiting is complete. Each flowering stalk is followed by a single folded-up leaf. Several of these neat structures poked through the ground all around us. Leaves were unfolding and were in various states, including the neat fully opened single leaves. I would not have known that this was an orchid!

You can read more about this species on the wikipedia article which has included the excellent botanical sketches of the flowers and leaves.

(All photographs were taken on 24 June 2023.)

Ground orchids: Meet the Corduroy Orchid Eulophia nuda

The monsoons bring a lot out of the landscape, including the seasonal ground orchids. This group have underground tubers and throw out an inflorescence in response to the rains. In Belgaum city (yea yea, Belagavi!), I met the Corduroy Orchid. These orchids are proliferating in the large green spaces of the city - a reminder of them being remnants of the western ghats forests that are not too far from the city. 

As if its overall look was not enough, the flowers have a lot of detail especially on the petal - the coloured lip as it were. This detail was perhaps the inspiration behind its common name - corduroy.

The variety of colours of this orchid stumped me - all risen beside each other. Check out this glorious one below we called "purple" for lack of better eye-sight. The corduroy pattern on this one was easily visible.

The other colour flowering was "pink".

The white inflorescence had the oldest flowers, at the bottom of the stalk, turning yellow. Was this perhaps a signal to insects that the flower had been pollinated?

The difference in colouration was stark - it had to be a signal to someone, or something. See the yellow below, followed by the white photographed from the same stalk.

This post has been put up in the early days of the monsoon (May 2024), and I could not wait for the fruits to form. Those will come soon. Also, in this species, the leaves emerge briefly after the flowering and fruiting is done. That too, fingers crossed, will be posted soon!

(All photographs taken in May 2024)