Criket hunter (Sphex funerarius) !

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If I’m telling you about wasps, what do you see, what do you imagine? Probably in your minds will appear a yellow and black flying bug that has, it is said, the despairing habit of stinging for free. And a first Google Image search will strengthen this representation. This wasp belongs to the genus Vespula, family Vespidae. There are also other very close wasps which are differentiated by larger size, pendant legs in flight and orange antennas: these wasps are called polistines or polistine wasps, belonging to the genus Polistes, family Vespidae. Without doubt have you ever heard of wasps and hornets, suggesting wasps and hornets are two distinct kind of creatures. But what if I told you hornets were wasps? From a taxonomic point of view, the term wasp is a catch-all term, which refers to countless species belonging to families, superfamily, and other different clades, with many different habits and aspects… Their only common point is to belong to the order Hymenoptera (which is also the case of bees, ants…). Thus, it is better to avoid using the term “wasp” alone, and one will prefer to specify which wasps it is (polistine wasp, ichneumon wasp…) or directly to use the scientific name or its direct translation (Polistes/polistine, Ichneumonidae/ichneumon…). All this speech to tell you not to be surprised to see this insect called “wasp”: it is indeed a member of the Sphecidae family, one of the many families of Hymenoptera that can be qualified as “family of wasp”…

Now let’s move on to the presentations. Our insect of the day is a female of Sphex funerarius (so, family Sphecidae). It’s a hunting wasp, not a social one like Polistes or Vespula, and even a digging wasp that will dig burrows into the ground. It is called “golden digging wasp” and females hunt some Orthoptera, especially crickets. These prey are not for adults, they feed on pollen, but for their terribly carnivorous larvae. Mom Sphex funerarius will first dig a burrow in the ground. Then it will be looking for an Orthoptera, like a grasshopper. Once found, it will paralyze it by stinging it several times near some nervous ganglia. The paralyzing venom works fast, and now the grasshopper is paralyzed, but alive. The wasp will then carry the grasshopper to its nest entrance. There it will inspect its burrow, then come out, catch the prey and lay it down at the bottom of its nest. Mom will lay an egg and seal the burrow. The egg will hatch and newborn larvae will gradually devour the grasshopper to develop. Jean-Henri Fabre, an entomologist known for his Entomological Memories, describes an interesting experience he carried out when the sphex visits its burrow before dropping its prey:

Here’s the fact: the moment the Sphex operates its home visit, I take the cricket, abandoned at the entrance of the nest, and places it a few inches further. The Sphex goes up, throws its ordinary shout, looks amazed here and there, and seeing its game too far, it walks out of its hole to go grab it and take it back to the right position. This done, it still coming down, but alone. Same manoeuvre from me, same disappointment of the Sphex upon arrival. Game is still reported to the edge of the hole, but the hymenopter still goes down alone; and so on, until my patience is tired. Kick on the shot, a quarantine of times, I repeated the same test on the same individual; its stubbornness defeated mine, and its tactic never varied.

Noticed in all the Sphex on which I have done the experiment in the same town, the adamant stubbornness I just described has not tired me of tormenting my mind for a while. The insect, I told myself, would therefore obey a fatal inclination, that circumstances cannot alter; its actions would be invariably settled, and the ability to acquire any experience, at its own expense, would be foreign to it.

-Jean-Henry Fabre, Souvenirs Entomologiques, série 1, chapitre 6

 

Thus, this bug would testify to some mechanical intelligence without any ability to adapt… The experience stroke the English-speakers so much that they created an adjective: “sphexish”, describing something (or someone) preprogramed, rigid. The name associated with the adjective was even created: “sphexishness”, as well as its opposite: “antisphexishness”. In fact, and although this “robotic” insect image has stayed, not all Sphex present this “mechanical loop”, as Fabre wrote it a few lines later:

The next year, in due course, I visit the same place. To dig the burrows, the new generation inherited the location elected by the previous generation; it has also faithfully inherited its tactics: the experience of the cricket yields the same results. These were last year’s Sphex, those are present year’s Sphex, also stubborn in an unsuccessful manoeuvre. The mistake was going to get worse, when a good fortune puts me in the presence of another Sphex colony in a canton distant from the first one. I start again my experiments. After two or three tests with the same result I have so often obtained, the Sphex starts to ride on the cricket, seizes it with the mandibles by the antennas and takes it immediately into the burrow. Who was silly? It was the experimenter foiled by the clever Hymenoptera. To the other holes, who earlier, who later, its neighbours vent my perfidies and enter their homes with the game, instead of stubbornly abandoning it for a moment on the threshold to seize it afterwards. What does this mean? The population I’m examining today, coming from another strain, as the sons return to the location chosen by the forefathers, is more skillful than the population of last year. The spirit of trick is passed on: there are more skilful tribes than other, apparently following the faculties of fathers. For the Sphex, as for us, the spirit changes with the province. – The next day, in another locality, I start the cricket test again. It succeeds indefinitely. I found a narrow-minded tribe, a true town of Beotians, as in my early observations.

-Jean-Henry Fabre, Souvenirs Entomologiques, série 1, chapitre 6

 


Last update: 29/10/2020

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