Ants Build Traps for Grasshoppers, Male Fruit Flies Orgasm

Insects are amazing beings and we need to be careful about thinking they're not.

Posted May 04, 2018

Two essays in a recent issue New Scientist magazine caught my attention because they focused on insects, nonhuman animals who often are written off as not all that smart or emotional. Each makes for good and easy weekend reading. 

The first piece by Jake Buehler is titled "Ants build a medieval ‘torture rack’ to catch grasshoppers," and while it is only available to subscribers to New Scientist, it's easy to summarize. Mr. Buehler begins, "Tropical ants build and set a trap that resembles a medieval torture rack. They use this ingenious setup to capture insect prey much larger than themselves, then rip the victim apart." His essay is based on a research paper that isn't available online by Markus Schmidt and Alain Dejean called "A dolichoderine ant that constructs traps to ambush prey collectively: convergent evolution with a myrmicine genus." These researchers note that the workers of this species of Costa Rican ant "builds along the branches of its host plant galleries that bear numerous holes slightly wider than a worker’s head. We noted that the workers hide, mandibles open, beneath different holes, waiting for arthropod prey to walk by or alight. They seize the extremities of these arthropods and pull backwards, immobilizing the prey, which is then spreadeagled and later carved up or pulled into a gallery before being carved up." And, as the grasshoppers try to work themselves free, they then step into another trap. What's also interesting is that farmers in the area where these ants live use fungicide, and in doing so they kill the fungus that's used to reinforce the traps.

The second essay by Andy Coghlan is called "Male fruit flies feel pleasure when they ejaculate" and is available online. His piece is based on a research paper, also available online, by Shir Zer-Krispil and her colleagues titled "Ejaculation Induced by the Activation of Crz Neurons Is Rewarding to Drosophila Males." Mr. Coghlan nicely summarizes this very interesting research project by noting, "Male fruit flies seem to enjoy ejaculation as much as men do. Their “orgasms” seem to be satisfying enough to reduce their craving for other rewards such as alcohol." Additional summaries of this research can be seen here

In this project, the researchers genetically engineered neurons in the abdomen of male fruit flies that were activated by red light. These neurons produce a chemical that makes the flies ejaculate called corazoninn, that also works to produce a neurotransmitter in flies' brains called F (NPF) that can be used to measure "levels of pleasure and reward." In a very novel and ingenious experiment, the researchers put normal and engineered males into a chamber, half of which was exposed to red light that could produce ejaculation in the engineered males but not in normal males. Mr. Coghlan writes, "When all the zones were unlit, the flies distributed themselves randomly. But when the red lights were turned on, many of the engineered flies congregated in the red-light zone. This suggests they enjoyed it there because of the automatic climaxing." The researchers also noted that after flies ejaculated, they weren't as attracted to alcohol-laced food as were males who hadn't. For more discussion please see "Male Fruit Flies Love to Cum, and Turn to Alcohol If They Can't" in which Becky Ferreira writes, "In this way, the study may have implications for substance addiction research, in addition to its insights about the underlying mechanics of sexual motivations in male flies. While sex and drugs are often mixed in our own human culture, it seems that fruit flies tend to opt for the latter when they fail to secure the former."

"Our findings exemplify the similarities in the principles that govern processing of natural rewards from flies to mammals, as the role of ejaculation in reinforcing mating experience is conserved."

University of Missouri Biologist Dr. Troy Zars agrees with the researchers' conclusions: “The team has shown that of all the behaviours involved in courtship and copulation, ejaculation – the final step – is rewarding to the fruit fly...They’ve also shown ejaculation changes levels of NPF, a signal of reward, in the fly brain.” Dr. Shohat-Ophir notes, “This sexual reward system is very ancient machinery, conserved from simple organisms all the way to us." 

It's obvious that one big question remains, namely, what about female fruit flies? Do they also experience pleasure from sex? This question is under investigation.

Please stand by for more discussion of the "surprising" cognitive and emotional lives of insects that stems from careful systematic comparative research. Who'd have thought they enjoy sex and set up torture traps? There really is so much to learn and we need to keep the door open to what they do and feel, and who they truly are. 

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