Nests

Bamboo specialists

Bamboo is an extremely favourable source of nesting space and nutrition for ants and other insects, as it is not only abundant but also a stable, clumped and fast growing resource. It harbours plant-sucking insects which are apt to form trophobiotic relationships with ants. Bamboo-specialized ants have been studied in the Asian and American tropics. 180,000 km2 of terra firme habitat in southwestern Amazonia are covered in forests dominated by Guadua bamboo (Bambusoidea, Poaceae; Nelson 1994), and many ant taxa naturally inhabit live and dead Guadua stems (Louton et al. 1996, Davidson et al. 2006). In Asia, various species belonging to Crematogaster, Dolichoderus, Pheidole, Polyrhachis arachne, Polyrhachis schellerichae and Tetraponera attenuata nest in dead or living culms of the bamboo Gigantochloa scortechinii.

Bamboo is a very tall and woody grass. It is characterized by a jointed stem called a culm. Typically the culms are hollow. Each culm segment begins and ends with a solid joint called a node. Nodes are are characterized by a swelling encircling the ends of the culm segments. The segments between the nodes are called internodes. From the nodes grow leaves and branches. Similar to the culms, the branches are also segmented with nodes and internodes.

The hollow internodes of bamboo culms, often made accessible by wood-boring insects, appear ideal nest sites for cavity-inhabiting ant species provided they can solve one unexpected problem with large bamboo stems in tropical environments: the holes, even small ones, are sufficient to allow runoff rainwater from the frequent torrential rainstorms to collect in the respective internodes, creating small, but long-lived bodies of water.

No bamboo ant (except Camponotus mirabilis and Tetraponera attenuata) opens its own entrances in nest culms, and bamboo specialists are thought to be parasites rather than mutualists of their hosts, despite a lack of hard evidence for effects on plant performance. While the ants are tightly adapted to their host plants, the bamboos do not actively provide the ants with nesting space. No advantage for the plant could be detected so far.

After culm walls have lignified, ants do not appear to be able to open entryways to unbreached internodes, and both live bamboo and dead bamboo specialists apparently depend either on entrances cut by other arthropods, or on cracks and fissures in fractured stems.