Why Do Termites Follow Ink Trails?


Worker and soldier termites follow an alcohol in ink that mimics a pheromone. (Sanjay Acharya)
Worker and soldier termites follow an alcohol in ink that mimics a pheromone. (Sanjay Acharya)


Termites are social insects that eat wood and other plant matter. Completely by accident, people discovered termites follow ink trails made by the black or blue ink from Bic and Papermate ballpoint pens. While they will follow a path made by other pens (85% of black ballpoints and 80% of blue ballpoints), they aren’t affected by red ink. They don’t follow ink trails made by rollerball pens or felt tip markers. The reason they follow some ballpoint pen lines is because the ink contains a chemical that acts as an insect pheromone.

Termite Pheromones and Ballpoint Ink

Worker and soldier termites are completely blind. They use the senses of touch and and “smell” to identify one another and enemies and to find food. When a termite locates food, it releases pheromones from its abdomen as it returns to the colony. The pheromones leave an invisible chemical trail other termites can smell to follow. The pheromone is volatile, meaning it is present in the air above the trail, so termites that get close to the trail without actually touching it can find their way.

Termites also follow trails produced by chemicals that mimic pheromones. These include alcohols and fatty acids. The blue and black ink in ballpoint pens contain the alcohol 2-phenoxyethanol (PE). PE is a volatile solvent that helps blue ink flow smoothly and dry quickly. However, the solvent doesn’t evaporate completely. In fact, the amount remaining in an ink line can be used in a forensic analysis to date documents written in ink.

When a termite encounters the ink trail, it thinks it has found a path to food. You can test this for yourself. Collect some termites. Draw a path using a blue Bic or Papermate pen. Any doodle works. Popular shapes include circles, lines, and figure eights. The project is so interesting, schools often use it in lesson plans to introduce students to the scientific method.

Watch Termites Follow an Ink Trail

Naturally, you might not be keen on having termites in your home because they might escape and cause property damage. You can watch what happens without keeping insect pets.

Ink Trails as Pest Control

If you have termites, you can’t just draw an ink line to guide them out of your home. However, you can use ink to lure them to a tasty pesticide treat they can bring back to the nest.

Cole Balkman demonstrated the technique’s effectiveness as a high school student for a science fair project. Balkman used a centrifuge to isolate 2-phenoxyethanol from ballpoint pen ink. He coated the inside of a bit of plastic tubing with the liquid. He ran the tubing through a piece of wall separating containers of termites and a piece of tissue paper soaked in the insecticide imidacloprid. Other containers of insects were connected to the tissue by clean tubing (no pheromones from ink). At the end of 72 hours, about 20% of the termites had died in the set-up with the clean tubing. However, 75% of the termites following the pheromone trail died.

So, if you have termites, you can perform some home pest control by drilling a small hole in the wall, coating the interior of a bit of plastic tubing with the proper ink, and offering tissue soaked in pesticide. In a home setting, be sure to put the poisonous tissue inside a sealed jar with a hole drilled in its lid for the tubing. Safety first!

Reference

  • Laporte, Gerald & D Wilson, Jeffrey & Cantu, Antonio & Amanda Mancke, S & L Fortunato, Susan. (2004). The Identification of 2-Phenoxyethanol in Ballpoint Inks Using Gas Chromatography/Mass Spectrometry – Relevance to Ink Dating. Journal of Forensic Sciences. 49. 155-9. doi:10.1520/JFS2003217
  • Tschinkel, Walter R.; Close, Peter G. (1972) The Trail Pheromone of the Termite, Trinervitermes trinervoides. J. Insect Physiol. Vol 19. pp. 707-721.

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