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A Plague of Locusts: Insects on the Move


(swarm of desert locusts in East Africa)


We recently posted a grasshopper dissection video here, where we discussed the anatomy of a grasshopper as well as many interesting facts about it. We left you off at the end of the video by mentioning the locusts- a terrifying swarm of grasshoppers.


Locusts and grasshoppers, if you haven’t realized yet, are not two different species of animals- ‘Locust’ is simply the name given to certain species of short-horned grasshoppers in the family Acrididae, that have a distinct solitary/swarming phase. Although these insects are mostly solitary, when overpopulation occurs, they go through a morphological and behavioral change called “density-dependent phenotypic plasticity.” Before we get into the details of the morphological/behavioral change, you may be wondering- “how does an artificial pressure like overcrowding make such a simple organism go through so much change?” Research shows that overpopulation leads to increased tactile stimulation of the insects’ hind legs, which then causes an increase in levels of serotonin produced, and all of the morphological/behavioral changes are this hormone’s doings.


The changes that occurs between the solitary and gregarious (swarming) phase of the locusts were so great, that even scientists mistakenly thought that the two phases were completely different species. The greatest difference between the solitary and gregarious phase of the locusts is behavioral. Gergaria nymphs are attracted to each other, forming and traveling in bands of 1000+ individuals, the collective unit often referred to as “outbreaks.” Morphological and developmental changes between the solitary and gregarious phases have been observed in certain species of locusts as well.


This topic of swarming gregarious locusts is much more relevant than it seems, due to the fact that outbreaks of these tiny critters have caused humans astronomical amounts of agricultural damage over history. Adult locust bands fly huge distances with their powerful wings, leaving destruction in their wake. Grasshoppers are capable of eating their weight in food every day, and their consumption of agricultural crops and vegetation have plagued multiple societies throughout history with famines. Although locusts’ swarming behaviors have decreased in the 20th century, the possibilities for another plague still looms if suitable climate conditions arise.


Scientists have developed numerous ways to prevent such plagues including monitoring systems, water-based contact pesticides, biological pesticides lethal to locusts, and more, but non of these methods have yet succeeded in completely eliminating the threat locusts pose. Although there is not much we as individuals can do to directly help with this problem, research has shown that climate change was linked to higher occurrence of locust plagues- hey, we can help against climate change, right? Spread awareness, recycle, conserve energy, reduce meat consumption, make informed decisions, you guys know the drill.




Sources:

https://www.nationalgeographic.com/animals/invertebrates/group/locusts/

http://www.fao.org/locusts-cca/bioecology/what-are-locusts/en/

https://www.deccanherald.com/science-and-environment/explained-what-are-locusts-and-how-are-they-harmful-842838.html


Photo credit: https://www.nationalgeographic.co.uk/environment-and-conservation/2020/02/plague-of-locusts-has-descended-east-africa-climate-change-may


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