Is the animal, on its side, right-handed, left-handed, or unbiased? We have had opportunities of showing that the Cricket, the Grasshopper and many others draw their bow, which is on the right wing-case, over the sounding apparatus, which is on the left wing-case. They are right-handed.
When you and I take an unpremeditated turn, we spin round on our right heel. The left side, the weaker, moves on the pivot of the right, the stronger. In the same way, nearly all the Molluscs that have spiral shells roll their coils from left to right. Among the numerous species in both land and water fauna, only a very few are exceptional and turn from right to left.
It would be interesting to try and work out to what extent that part of the zoological kingdom which boasts a two-sided structure is divided into right-handed and left-handed animals. Can dissymetry, that source of contrasts, be a general rule? Or are there neutrals, endowed with equal powers of skill and energy on both sides? Yes, there are; and the Spider is one of them. She enjoys the very enviable privilege of possessing a left side which is no less capable than the right. She is ambidextrous, as witness the following observations.
When laying her snaring-thread, every Epeira turns in either direction indifferently, as a close watch will prove. Reasons whose secret escapes us determine the direction adopted. Once this or the other course is taken, the spinstress does not change it, even after incidents that sometimes occur to disturb the progress of the work. It may happen that a Gnat gets caught in the part already woven. The Spider thereupon abruptly interrupts her labours, hastens up to the prey, binds it and then returns to where she stopped and continues the spiral in the same order as before.
At the commencement of the work, gyration in one direction being employed as well as gyration in the other, we see that, when making her repeated webs, the same Epeira turns now her right side, now her left to the centre of the coil. Well, as we have said, it is always with the inner hind-leg, the leg nearer the centre, that is to say, in some cases the right and in some cases the left leg, that she places the thread in position, an exceedingly delicate operation calling for the display of exquisite skill, because of the quickness of the action and the need for preserving strictly equal distances. Any one seeing this leg working with such extreme precision, the right leg to-day, the left to-morrow, becomes convinced that the Epeira is highly ambidextrous.
Age does not modify the Epeira’s talent in any essential feature. As the young worked, so do the old, the richer by a year’s experience. There are no masters nor apprentices in their guild; all know their craft from the moment that the first thread is laid. We have learnt something from the novices: let us now look into the matter of their elders and see what additional task the needs of age impose upon them.