Whoever is able to feel a hundred molecules of matter in a cubic meter of air is a butterfly.
Nature is a very inventive and skillful engineer. Every living being is unique and amazing. One such creature is a butterfly. Some species of butterflies are ideal organs of chemical sense, because their sense of smell and taste, if not perfect, then close to this.
Why are we considering both smells and taste in one article? The point is that both senses are based on chemoreceptors. Only the sense of smell is a determination of the presence of certain substances in the air, and the taste is the same, only in a humid environment. In butterflies, the sense of smell works thanks to the antennae, and the taste thanks to the mouth organs.
Let's start with smell
In most insects, the so-called olfactory sensilla is responsible for the sense of smell. Their shape is most often conical. Sensilla are located, as mentioned above, on the antennae. The larger the sensilla, the more sensitive the insect to odors.
For example, bees have about 6,000 sensilla on their antennae. Other insects may have more. In some species of butterflies, the number of sensilla on one antenna reaches several thousand. And in a species such as Antheraea polirhemus, the number of sensilla exceeds 60,000.
Electron micrograph of a portion of the antennae of the cornworm (Helicoverpa zea Boddie) with trichoid sensilla (after Lee and Baker, 2008). Source
Sensilla are associated with specialized groups of neurons. There are several dozen of them in each group. Sensillas are porous, they act as traps of chemical molecules. Those, getting into the pores, interact with the processes of neurons, which, in turn, send an electrical signal to the nervous system. This is the definition of smell.
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Many people know that male butterflies, especially nocturnal ones, have comb antennae and sense the presence of a female for many kilometers. All thanks to the huge amount of sensilla. Females emit pheromones, and males catch them and flock to the source. Accordingly, the inheritance can be left by those who have the most sensitive sense of smell (well, or who, by a happy coincidence, was the closest of all, which is also logical).
Entomologists have repeatedly experimented with Saturnias. So, released from the window of a moving train at different intervals, male butterflies were able to return to the female, which was up to 12 km away from them. The males were tagged, and about 26% of them were able to find the object of their adoration from a distance of 11 km.
It is known that male butterflies are able to capture female pheromone molecules, being 3-6 km away from them. A species such as pear saturnia (pear peacock eye) is capable of even more impressive gender feats, sensing the presence of a female 10 km away. At the moment, pear saturnia ranks first in the list of "living odor detectors" among insects. Males of silkworms need 100 pheromone molecules per 1m 3 in order to find a female.
Other insects, of course, also smell. So, herbivorous arthropods determine the plants that suit them just by smell. Sometimes it may seem that such an insect is just wandering in search of food, but this is not so - it goes to its goal, albeit not in a straight line.
Scavengers, flies, mosquitoes and other insects that delight us determine their food by smell. It has long been known that the majority of social insects also identify "friends" by smell. If an alien of the same species accidentally enters the colony, it is driven away or killed. Well, what, it smells wrong.
What about taste?
Here, too, everything is in order - insects are almost ideal detectors for the presence of a variety of chemicals in liquids and solids. Moreover, their taste organs are located in the mouth organs, on the antennae, the forelegs (hello to the same butterflies) or even the ovipositor. True, in the latter case, it is not just about taste, but about the chemical characteristics of the substrate in which the eggs will be laid.
As for butterflies, when they touch the sweet substance with their front legs, their proboscis immediately reacts. By the way, butterflies 'feet' feel much lower concentrations of substances than humans - they are about 2000 times more sensitive. Scientists have determined that representatives of Lepidoptera are able to distinguish different substances from each other, including very weak solutions of quinine, sucrose, etc.
The taste detectors are based on the same sensilla, nature decided not to reinvent the wheel. Only in this case, the sensilla is thick-walled, and at the base of each there are not several tens, but 3-5 neurons. In rare cases, their number reaches 50 - this is for a few taster species. The principle of operation is the same here: through the pores, the chemical penetrates to the top of the neuron and interacts with it.
Interestingly, in many cases, the neurons at the base of the gustatory sensilla are highly specialized. An example is the Phormiaregina fly, in which groups of neurons consist of only three elements. But then one neuron - tactile, the second - determines the sweet taste, the third - salty. All a fly needs is sweet food, so it doesn't need to define more tastes.
But in other insects, for example, bees, neurons are more functional. They can define all tastes - sweet and salty, sour or bitter. The sensitivity of most insects to taste is about the same or slightly higher or lower than that of humans. All the same butterflies have distinguished themselves here.
Is this where the superpowers of butterflies end?
No, they are still able to distinguish infrared radiation and hear ultrasound. As for the first ability, it gives them the ability to find flowers in complete darkness or identify a partner.
But ultrasound is a forced evolutionary tool. "Ultrasonic echo sounder" allows butterflies to avoid bats, hearing the sounds they make. In addition, some butterflies use echolocation in some way for orientation in space. As far as can be understood, they do not emit ultrasound, but are guided by reflected sounds. This ability enables them to avoid obstacles.
