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Harmonic Radar

What is harmonic radar you ask? In short, it is a method to track insects.

Now, I understand that tracking insects doesn’t sound nearly as cool as tracking lions on an African safari through the Serengeti – but I promise, it’s still really cool in its own way.

How it Works

The way harmonic radar works is that a standard radar device produces a high-power radio-frequency pulse that transmits directional signals to a tag/antenna that has been placed on an insect (Colpitts & Boiteau 2004; Pilkay 2013). Then, the tag/antenna on the insect sends back a second signal to the radar device (Colpitts & Boiteau 2004; Pilkay 2013). So simply, an insect is adorned with an antenna that receives and transmits a signal that allows for scientist to track the insect’s location and travel path.

You might be thinking to yourself, why this this important? Well, because of this technology, scientists and conservationists have been able to attempt to better study species that have posed a challenge in the past.

Two different types of harmonic radar systems.
Left (Milanesio et. al 2017), Right (Riley and Smith 2002).

Benefits

Traditionally insect tracking was limited to the mark-release and re-recapture method, where scientists would individually catch, tag, and release insects back into their natural habitat with the hopes of re-capturing them later (Hall & Hadfield 2009; Lee et al. 2013). Studying insect movement with the mark and re-capture method tend to lead to imprecise or incomplete data collection, due to detectability issues like small body size and habitat constraints such as dense vegetation (Hall & Hadfield 2009; Kim et al. 2016; Lee et al. 2013). By using harmonic radar technology, these common roadblocks to accurately study insect movement can be reduced! Also, with harmonic radar technology, scientists can modify or enhance the base technology in order to suit their specific research needs – allowing for new insight on a wide variety of entomological (insect) research.

Real-World Applications

Harmonic radar technology has been used in different conservation efforts to track multiple species for a variety of different reasons. One study looked at tracking an endangered endemic (native) tree snail species in Hawai’i in order to understand the impacts of habitat fragmentation and introduced species on the tree snail population (Hall & Hadfield 2009). Some studies use harmonic radar to assess the movement patterns of economically beneficial insects to agriculture in order to better manage these species (Boiteau and Colpitts 2004; Boiteau et. al 2011; Kim et. al 2016; Pilkay 2013). Another scientist was interested in studying effects of emerging pathogens that are altering the homing ability of honeybees, leading to a decline in the colony and the spread of the pathogen to new colonies (Wolf 2014). While other scientists have used harmonic radar technology to track an invasive species of hornet, that was threatening native honeybee colonies in Southern Europe, so they could track the hornets back to their nests in order to improve eradication efforts (Milanesio et. al 2016; Milanesio et. al 2017).

Examples of harmonic radar tags fixed to yellow-legged Asian hornet (Vespa velutina).
Left (Milanesio et. al 2017), Right (Milanesio et. al 2016).

Weaknesses

Just like anything else, harmonic radar is not perfect. Even though an advantage of using harmonic radar is to be able to better track insects in their natural habitats, some researchers have reported lost data due to insects flying too low to the ground and out of range, flying too close together so individual data gets scrambled, and natural barriers like hills or mountains interfering with radar signals (Osborne et. al 1999; Riley and Smith 2002).

Honeybee with harmonic radar transponder. (Capaldi et. al 2000).

Another barrier to harmonic radar is ensuring minimal to no impact or alteration of the insect’s natural behavior due to the tag (Boiteau et al. 2011; Lee et al. 2013; Hall & Hadfield 2009). Harmonic radar tags are lightweight since they do not rely on a battery (Lee 2016). However, it is also important to ensure that the adhesive used to secure the device to the insect will not be harmful (Lee et. al 2013; Lee 2016) and that the tag will not impact the insect’s natural movements due to weight in proportion to their body size or by becoming entangled on vegetation (Boiteau et. al 2010; Boiteau et. al 2011).

Final Thoughts

Insects play a larger role than most people know in the overall health and function of our world’s ecosystems – so studying them is an important piece to science and conservation. Overall, harmonic radar is an interesting and useful piece of technology being used in conservation and science to better understand the natural world. With the continued use, understanding, and enhancement of harmonic radar technology and countless other conservation focused technologies, we might just be able to save the world.

References

  1. Boiteau, G., and B. Colpitts. (2004). The potential of portable harmonic radar technology for the tracking of beneficial insects. International Journal of Pest Management 50(3), 233-242.
  2. Boiteau, G., C. Vincent., F. Meloche., T. C. Leskey. (2010). Harmonic Radar: Assessing the Impact of Tag Weight on Walking Activity of Colorado Potato Beetle, Plum Curculio, and Western Corn Rootworm. Journal of Economic Entomology 103(1), 63-69.
  3. Boiteau, G., C. Vincent., F. Meloche., T. C. Leskey., and B. G. Colpitts. (2011). Evaluation of Tag Entanglement as a Factor in Harmonic Radar Studies of Insect Dispersal. Environmental Entomology 40(1), 94-102.
  4. Capaldi, E. A., A. D. Smith., J. L. Osborne., S. E. Fahrbach., S. M. Farris., D. R. Reynolds., A. S. Edwards., A. Martin., G. E. Robinson., G. M. Poppy., and J. R. Riley. (2000). Ontogeny of orientation fight in the honeybee revealed by harmonic radar. Nature 403, 537-540.
  5. Colpitts, B. G., and G. Boiteau. (2004). Harmonic Radar Transceiver Design: Miniature Tags for Insect Tracking. Transactions on Antennas and Propagation 52(11), 2825-2832.
  6. Hall, K. T., and M. G. Hadfield. (2009). Application of harmonic radar technology to monitor tree snail dispersal. Invertebrate Biology 128(1), 9–15.
  7. Kim, J., M. Jung., H. G. Kim., and D. H. Lee. (2016). Potential of harmonic radar system for use on five economically important insects: Radar tag attachment on insects and its impact on flight capacity. Journal of Asia-Pacific Entomology 19, 371-375.
  8. Lee, D. H. (2016). Evaluating effects of harmonic radar tag attachment on the survivorship and dispersal capacity of Riptortus pedestris (Hemiptera: Alydidae). Florida Entomologist 99(1), 110-112.
  9. Lee, D. H., Wright, S. E., Boiteau, G., C. Vincent., and T. C. Leskey. (2013). Effectiveness of Glues for Harmonic Radar Tag Attachment on Halyomorpha halys (Hemiptera: Pentatomidae) and Their Impact on Adult Survivorship and Mobility. Environmental Entomology 42(3), 515-523.
  10. Milanesio, D., M. Saccan., R. Maggiora., D. Laurino., and M. Porporato. (2016). Design of an harmonic radar for the tracking of the Asian yellow-legged hornet. Ecology and Evolution 6(7), 2170-2178.
  11. Milanesio, D., M. Saccan., R. Maggiora., D. Laurino., and M. Porporato. (2017). Recent upgrades of the harmonic radar for the tracking of the Asian yellow-legged hornet. Ecology and Evolution 7, 4599-4606.
  12. Osborne, J. L., S. J. Clark., R. J. Morris., I. H. Williams., J. R. Riley., A. D. Smith., D. R. Reynolds., and A. S. Edwards. (1999). A landscape-scale study of bumble bee foraging range and constancy, using harmonic radar. Journal of Applied Ecology 36, 519-533.
  13. Pilkay, G. L., F. P. F. Reay-Jones., and J. K. Greene. (2013). Harmonic Radar Tagging for Tracking Movement of Nezara viridula (Hemiptera: Pentatomidae). Entomological Society of America 42 (5), 1020-1026.
  14. Riley, J. R., and A. D. Smith. (2002). Design considerations for an harmonic radar to investigate the flight of insects at low altitude. Computers and Electronics in Agriculture 35, 151-169.
  15. Wolf, S., D. P. McMahon., K. S. Lim., C. D. Pull., S. J. Clark., R. J. Paxton., and J. L. Osborne. (2014). So Near and Yet So Far: Harmonic Radar Reveals Reduced Homing Ability of Nosema Infected Honeybees. PLOS ONE 9(8), 1-15.
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