Chapter 11 Sawfly

If you walk in the garden, you will find that there are some delicate holes on the leaves of lilac or rose, some are round and some are oval, as if someone has cut them skillfully.Some leaves have so many holes that only the veins remain.Who did this?And why do they do this?Is it because it's delicious, or because it's fun?These things are done by wood sawflies. They use their mouths as scissors, and rely on their eyes and body movements to cut off the small leaves.They do this not because they think it is delicious, nor for fun, but these small cut leaves are really important in their lives.They make these many small leaves into needle-shaped pouches, in which honey and eggs can be stored.Each nest of the sawfly has a needle-shaped pocket, which is stacked on top of one another.

The wood sawfly we often see is white with stripes.It often lives in the tunnels of earthworms. If you go to the mud flat and squat down to search carefully, it is not difficult to find such tunnels.Wood sawflies do not use the entire tunnel as their residence, because the depths of the tunnel are often dark and damp, and it is not suitable for excreting waste, and sometimes they are attacked by insects.So it uses the seven or eight inches long section near the ground as its dwelling place. The sawfly will encounter many natural enemies in its life. After all, the tunnel is not a safe and strong fortification. How can it strengthen the protection of its homeland?Lo and behold, those leaf clippings are coming in handy again.It clogs up the depths with the many fragmentary leaflets it clips.These small blades for plugging are all carelessly snipped from the leaves by the wood sawfly.So it looks very fragmented, not as neat as those small leaves used for nesting.

Above the fortifications of the wood sawfly there is a stack of small nests, maybe five or six.These small nests are made of small leaves cut by the wood sawfly. These small leaves for nesting are much more demanding than those used for fortifications. They must be broken leaves of equal size and shape, round The leaves are used for the cover, and the oval leaves are used for the base and edges. The small leaves of the wood sawfly are all cut with its small knife - the corner of its mouth.In order to meet the requirements of various parts of the nest, it often uses these scissors to cut out small leaves of different sizes.For the bottom of the nest, it is often carefully designed, not ambiguous at all.If a larger leaf cannot completely fit the section of the tunnel, it will use two or three smaller oval leaves to form a nest bottom until it closely matches the section of the tunnel without leaving any gaps.

The cover of the nest is a perfectly round leaf.It seemed to have been precisely planned with compasses, and would fit perfectly over the nest. After a series of small nests are made, the sawfly cuts off many leaves of different sizes and twists them into a plug to plug the tunnel. Most worthy of our consideration is that the sawfly has nothing to use as a model.How is it able to cut so many precise leaves?Does it have a model to follow?Or is there any special instrument to measure it?Some people speculate that the body of the sawfly can be used as a compass, one end is fixed, that is, the tail is fixed on a certain point on the blade; the other end, which is their head, rotates on the blade like the feet of the compass.This will cut out a standard circle.Just like our arms, the fixed shoulder is a circle when it is waved.But our arms do not draw circles of the same size with such skill and precision as the wood sawp wasp, and these circular leaves, which are used for the cover of the nest, fit seamlessly over the nest and are perfect.And the small nest is under the tunnel, so they don't know how to measure the size of the small nest at any time. They only rely on the feeling they get to determine the size of the leaf cover that the small nest needs.

The leaves are round and cannot be cut too large or too small.If it is too big, it cannot be covered, and if it is too small, it will fall into the small nest, suffocating the eggs.You don't have to worry about the wood sawfly's technique. It can cut the required leaves from the leaves very skillfully. Although there is no mold, it is so precise.Why does the wood sawfly have such a profound foundation in geometry? One night in winter we all sat around the stove.I remembered the thing about the sawfly cutting the leaves, so I designed a little experiment. "Tomorrow is market day, and one of you has to go out and get what you need for the week. The cat broke the lid on a pot we use every day in the kitchen. I asked him to buy a lid and come back, not too big or too small." , just enough to cover our jar. Before we went to buy it, we allowed him to carefully estimate the size of the jar, but not by anything, and then go to the market tomorrow and choose the appropriate lid from memory. "Everyone was embarrassed when they heard this, and no one dared to stand up and take on this task immediately.

Indeed, this seems to be a difficult task.But the sawfly's work is more unpredictable than ours. It does not see its own nest lid, and has no such impression at all; Compare each other to choose a most suitable cover.For the saw-bee it is necessary, at a great distance from its home, to cut without hesitation a large round leaf, which will just fit for the cover of its nest.What seems difficult to us is child's play to it.If we don't have a measuring tool, such as a string, or a model or a pattern, it is difficult for us to choose a cover that is the right size.But the wood sawfly doesn't need anything.They are indeed much smarter than we are about how to run a family.

It is true that the sawfly outperforms us in problems of practical geometry.When I saw the nest and cover of the wood sawfly, and observed the miracles created by other insects in terms of "technology" - those are not what our structure can explain, I have to admit that our science is far behind them .