It was hiding on the underside of the sea hibiscus, two of its tarsi clipped to the edge of the heart-shaped leaf, betraying its presence. Gingerly, I flipped the leaf over and my heart skipped a beat, for my initial hunch was right: a tiny walking leaf!
It tended to stagger from side to side before settling down, possibly mimicking the movement of a leaf in the wind. We also observed it chewing on the browning edges of a dying sea hibiscus leaf, a behaviour which raises some questions: don’t most herbivores prefer young to mature leaves? Is this species of leaf insect a generalist or a specialist (is the sea hibiscus its host)? Why is it so willingly feeding on an old leaf? I’d like to do some proper research into it sometime (as I do for a lot of other curiosities), but a paper by Blüthgen & Metzner (2007) on the feeding preferences of tropical stick insects satisfies for the moment:
Both specialists significantly preferred young leaves over old leaves of their respective host plants. In contrast, both generalists significantly preferred old leaves of the hosts of the specialist A. margaritatus. To reveal whether differential feeding choices were triggered by foliar chemistry, extracts (water, acetone, and hexane) of young leaves were applied to discs from old leaves and vice versa, and subjected to similar choice tests. For both Mallotus species, experimental results suggest that four chemical functions act in concert: (1) young leaves contain deterrents against generalists and (2) stimulants for specialists. Moreover, (3) old leaves contain deterrents against specialists and (4) stimulants for generalists. Deterrent compounds in young and old leaves, respectively, appeared in extracts using different solvents, suggesting the activity of multiple classes of secondary metabolites. Our study thus reveals that plant defences and herbivore offences are partly structured by leaf ontogeny and herbivore specialisation in a tropical plant-herbivore system.
Fascinating stuff.
This pretty wee thing has just made my week.
Not much else at Buloh today. Crocs, otters, and the other usual. The rain was unrelenting.
Leaf insect nymph (Phyllium ?siccifolium)
Heavy jumper female (Hyllus diardii)
Moth caterpillars
Exposed ‘Spittle bug’ / froghopper nymph
Otters in the distance in the rain