The fact that glow worms routinely eat snails is well established. I have on umpteen occasions seen a glow worm making a meal of a snail.
Till now, however, I had not had an opportunity to actually witness the ‘hunt'. It was during a visit to Old Magazine House, Ganeshgudi that I got lucky. It was October and the tail end of the monsoon season. The overcast sky and the occasional drizzle were a constant reminder that monsoon was still active.
Despite the drizzle, I stepped out early in the morning, armed with an umbrella, and went down the path leading to the gate of Old Magazine House. I was stopped in my tracks by what I saw on the ground just at the edge of the track – a mass of froth! I was not sure as to what could have created such a large volume of froth.
I looked around and saw a snail and wondered if the snail could have produced it. But then, I had never heard of snails producing froth.
My attention was drawn to a glow worm moving about actively in the vicinity. There was an adrenalin rush in my system. Was there going to be an interaction between the glow worm and the snail? Will the glow worm attack the snail and devour it? These were questions that were going on in my mind. All these were immensely possible events and I could be a witness to it!
The glow worm came close to the snail, perhaps by using the slime trail that a snail leaves behind. It walked about the snail and followed it for a while.
It attacked the snail once and got its mandibles into the soft flesh. The snail retracted and the glow worm was caught between the body of the snail and the hard shell. It quickly wriggled out and wandered about only to come back to the snail. This time it bit the snail on the tentacle. The snail withdrew only that tentacle and did not evert it to its full length for as long as I observed it!
The glow worm after wandering about some more, came back and this time climbed on to the snail's shell and waited there looking for an opportunity to bury its mandibles into the snail. It managed to do so and the snail's reaction was identical to the previous occasion. The glow worm was in also in a similar situation and was forced to withdraw. It eventually climbed back on to the shell of the snail.
Throughout this drama, I noticed the glow worm continuously cleaning itself. For this purpose it used a brush-like organ (pygopod) on the last segment of its abdomen. This organ is used for both locomotion and cleaning.
The snail moved a bit and stopped. It also withdrew into the shell more or less completely and started producing the froth again.
The glow worm that was riding the snail dismounted and moved about in the vicinity of the snail.
It eventually settled down in one place and started cleaning itself continuously for a few minutes. After this intense frantic bout of cleaning, it became motionless and led me to suspect that it was paralyzed or even dead.
The watch continued with a hope that something more would transpire. Eventually, the glow worm became active and started walking about. The snail by now had produced enough froth to cover itself and this froth kept the glow worm at bay. As the morning progressed, the incessant drizzle became heavy and gradually thinned the froth. The snail now started moving about and went on its way. The glow worm did not show any interest in the snail and wandered off far away from the snail.
Only when the snail and the glow worm parted ways, leaving in their wake many unanswered questions, did I realize that I had watched this interaction for over an hour!