FLYING SPIDERS.
Often, in summer, the bushes are covered with threads, attached by one end, blowing out in the wind; and bits of cobweb are blowing about, with occasionally a spider attached. To account for such threads, curious theories have been thought of; among others, that spiders are able to force the thread from their spinnerets, like water from a syringe, in any direction they choose.
If a spider be put on a stick surrounded by water, she manages, in course of time, to get a thread to some object beyond, and to escape by it. To find out how this is done, Mr. Blackwall tried some experiments. He put spiders on sticks in vessels of water, and they ran up and down, unable to escape as long as the air in the room was still. But, if a draught of air passed the spider, she turned her head toward it, and opened her spinnerets in the opposite direction. If the draught continued, a thread was drawn out by it, which at length caught upon something, when the spider drew it tight, and escaped on it. If the air was kept still, or the spider covered with a glass, she remained on the stick till taken off.
These experiments have been repeated, and show that the spider does not shoot or throw the web in any way, but takes advantage of currents of air, and allows threads to be blown out to a considerable distance.
There is a still more curious use of this method of spinning threads; that is, in flying. Small spiders, especially on fine days in the autumn, get up on the tops of bushes and fences, each apparently anxious to get as high as possible, and there raise themselves up on tiptoe, and turn their bodies up, as in [Fig. 40], with their heads toward the wind, and spinnerets open. A thread soon blows out from the spinnerets, and, if the current of air continues, spins out to a length of two or three yards, and then offers enough resistance to the wind to carry the spider away with it up into the air. As soon as she is clear, the spider turns around, and grasps the thread with her feet, and seems to be very comfortable and contented till she strikes against something. Sometimes they rise rapidly, and are soon out of sight; at other times blow along just above the ground.
Fig. 40.
This habit is not confined to any particular kinds of spiders, but is practised by many small species of Erigone, and by the young of many spiders of all families, that, when adult, would be too large for it. The majority of the spiders flying in autumn are the young of several species of Lycosa, that seem to spend the greater part of October and November trying to get as far above ground as possible. The best places to watch them are garden-fences in cities, where they often swarm, and can be more distinctly seen than on bushes. Large numbers can always be seen, for example, on the fences around the Common in Boston, every fine day in autumn, until there has been a long period of cold weather. Other species fly in the early part of summer.
Mr. Blackwall observed in Manchester, Eng., Oct. 1, 1826, a calm sunny day, that, just before noon, the fields and hedges were covered over with cobwebs. So thick were they, that, in crossing a small pasture, his feet were covered with them. They had evidently been made in a very short time, as early in the morning they were not conspicuous enough to attract his attention, and the day before could not have existed at all, as a high wind blew all day. At the same time large rags of web were floating about in the air, one measuring five feet long, and several inches wide. These appeared to be not formed in the air, but torn from grass and bushes, where they were produced by the tangling of many threads which had been spun separately. They kept rising all the forenoon, and in the afternoon came down again. Not one in twenty had a spider on it. Similar large webs were observed by Lincecum in Texas, and supposed by him to be balloons spun purposely by the spiders.
Mr. Darwin, in the journal of the voyage of “The Beagle,” says, that when anchored in the River Plata, sixty miles from shore, he has seen the rigging covered with cobwebs, and the air full of pieces of web floating about. The spiders, however, when they struck the ship, were always hanging from single threads, and never to the floating webs.
A recent account of the signs of weather-changes near the southern coast of the United States mentions as one of them cobwebs in the rigging.
It is still unexplained how the thread starts from the spinnerets. It has been often asserted that the spider fastens the thread by the end, and allows a loop to blow out in the wind; but, in most cases, this is certainly not done, only one thread being visible. Sometimes, while a thread is blown from the hinder spinnerets, another from the front spinnerets is kept fast to the ground, [Fig. 41]; so that, when the spider blows away, it draws out a thread behind it entirely independent of the one from which it hangs.
Fig. 41.
Sometimes, instead of a single thread, several are blown out at once, like a long brush, as in [Fig. 42], which represents, four times enlarged, an unusually large spider just before blowing off a fence.
Fig. 42.
CHAPTER IV.
GROWTH OF SPIDERS.
Persons unfamiliar with spiders find it hard to tell young from old, and male from female. This is caused, in part, by the great differences between different ages and sexes of the same spider, on account of which they are supposed to belong to distinct species.
The adult males and females are easily distinguished from each other, and from the young, by the complete development of organs peculiar to each sex, which will be described further on.
The males are usually smaller than the females, and have, in proportion to their size, smaller abdomens and longer legs. They are usually darker colored, especially on the head and front part of the body; and markings which are distinct in the female run together and become darker in the male. In most species these differences are not great; but in some no one would ever suppose, without other evidence, that the males and females had any relationship to each other. The most extreme cases of this kind are Argiope and Nephila, where the male is about a tenth as large as the female. [Fig. 43] represents male and female of Nephila plumipes described by Wilder.
Fig. 43.
Fig. 44.
Fig. 45.
The female of one of the common crab spiders is white as milk, with a crimson stripe on each side of the abdomen; while the male is a little brown-and-yellow spider, with dark markings of a pattern common in the family to which it belongs.
In the genus Erigone, which includes the smallest known spiders, the males often have curious humps and horns on their heads, [Fig. 44]. The most extreme example is [Fig. 45], where the eyes are carried up on the end of the horn. The females of all these species have plain round heads; and what use the humps are to the males nobody knows.
The peculiar organs by which the adult males and females can always be distinguished are, in the males, the palpal organs, on the ends of the palpi; and, in the females, the epigynum, [Fig. 1].