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THE
STRUCTURE AND HABITS
OF
SPIDERS.
BY
J. H. EMERTON.
[Illustration]
_ILLUSTRATED._
BOSTON:
S. E. CASSINO & CO., PUBLISHERS.
1883.
COPYRIGHT.
BY S. E. CASSINO.
1878.
_Electrotyped_
_By C. J. Peters & Son,_
_Boston._
PREFACE.
The object of this book is to give a plain account of the best known
habits of spiders, and as much of their anatomy and classification as
is necessary to understand these habits. The portion on the spinning
and flying habits is copied chiefly from Blackwall and Menge; that
on the trap-door spiders from Moggridge; and the habits of Nephila
and Hyptiotes, from Wilder. The observations of these authors have
been repeated as far as possible, and some changes and additions made
to their accounts of them. The numerous stories of deadly poison,
supernatural wisdom, and enormous size and strength of spiders, have
been omitted as doubtful. Several cuts from the papers of Professor
Wilder have been repeated by favor of the author and publishers. Most
of the figures are, however, new, and engraved by photography from my
own drawings.
CONTENTS.
CHAPTER I.
PAGE
Anatomy and Classification.—External Parts of a Spider.—Feet.
—Palpi and Maxillæ.—Mandibles.—Breathing-Holes.—Epigynum.
—Spinnerets.—Eyes.—Colors and Markings.—Internal Organs.—
Intestine.—Heart.—Breathing-Organs.—Nervous System.—
Poison Glands.—Families of Spiders 11
CHAPTER II.
Eating and Biting.—Structure of the Mandibles.—Mouth.—Eating
Insects.—Biting.—Experiments on Poison of Spiders.
—Tame Spiders 32
CHAPTER III.
Spinning-Habits.—Spinnerets.—Spinning-Glands.—Beginning
of a Thread.—Holes and Nests.—Burrows of Lycosa.—Trap-door
Nests.—Tubes and Nests of Drassidæ.—Webs of Agalena.—Webs
of Linyphia and Theridion.—Spiders living in Webs made by
Others.—Round Webs.—Epeira Vulgaris.—Zilla.—Nephila.—
Habits in the Web.—Curled Webs.—Cribellum and Calamistrum.
—Webs of Amaurobius.—Regular Webs of Dictyna.—Triangle
Web.—Round Webs with Curled Thread 38
CHAPTER IV.
Growth of Spiders.—Differences between Male and Female.—
Differences between Old and Young.—Male and Female of Nephila
and Argiope.—Heads of Male Erigone.—Palpal Organs.—Epigynum.
—Use of Palpal Organs and Epigynum in Various Spiders.—Laying
Eggs.—Cocoons of Drassus, Attus, and Epeira.—Cocoons of
Argyrodes and Argiope.—Care of the Cocoon.—Parasites.—Growth
in the Egg.—Hatching.—Habits of Young Spiders.—Moulting.
—Habitats of Spiders.—Distribution of Spiders 86
LIST OF ILLUSTRATIONS.
PAGE
1. Under Side of Epeira Vulgaris 13
2. Foot of Epeira Vulgaris 14
3. Foot of Attus Mystaceus 15
4. Upper Side of Epeira Vulgaris 18
5. Section of Epeira Vulgaris 20
6. Mygale Hentzii 24
7. Dysdera Interrita and Eyes 26
8. Drassus 26
9. Agalena Nævia 27
10. Lycosa and Eyes 28
11. Salticus and Eyes 29
12. Thomisus and Eyes 30
13. Theridion 31
14. Mandibles of Epeira Vulgaris. Front View 33
15. Claw of Mandible 33
16. Spinnerets of Epeira Vulgaris 39
17. Single Spinning Tube 40
18. Spinning-Glands 40
19. Spinneret of Prosthesima 41
20. Spinneret of Agalena with some of the hairs removed 41
21. End of Thread 42
22. Trap-door Nests. Copied from Moggridge 47
23. Nest of Dolomedes 52
24. Web of Agalena 55
25. Web of Linyphia Marmorata 57
26. Web of Linyphia Communis 59
27. Pholcus swinging 61
28. Round Web of Epeira Vulgaris 62
29. Web of Zilla 65
30. Web of Nephila Plumipes. From Wilder 66
31. Part of Web of Nephila, to show the smooth threads.
From Wilder 67
32. Epeira Spinea 69
33. Spinnerets of Amaurobius 72
34. Calamistrum of Amaurobius 73
35. Dictyna spinning Curled Web 73
36. Part of Web of Amaurobius 74
37. Part of Web of Dictyna, showing regular arrangement
of threads 75
38. Unfinished Web of Triangle Spider. From Wilder 76
39. Finished Web of Triangle Spider, and Spider holding
the Web. From Wilder 78
40. Young Lycosa flying 81
41. Flying Spider with a Thread attached to the Ground 84
42. Large Attus flying by a Brush of Threads 85
43. Male and Female Nephila Plumipes. From Wilder,
in Proceedings Boston Society Natural History 78
44, 45. Heads of Males of Several Species of Erigone 88, 89
46. Palpal Organ of Mygale 89
47. Palpal Organ of Epeira 90
48. Palpal Organ of Theridion 91
49. Epigynum of Epeira Riparia 92
50. Epigynum of Theridion 93
51. Epigynum of Theridion 94
52. Copulation of Lycosa 95
53. Copulation of Linyphia 96
54. Copulation of Agalena 96
55. Copulation of Epeira Riparia 97
56. Drassus laying Eggs 99
57. Lycosa carrying Cocoon attached to her Spinnerets 100
58. Attus Mystaceus laying Eggs 101
59. Epeira Strix making Cocoon 101
60. Epeira Strix laying Eggs 102
61. Cocoon of Argyrodes hanging by a Stem 103
62. Cocoon of Epeira Riparia. From Wilder 103
63. Eggs during Segmentation 106
64. Eggs further Advanced 108
65. Young Epeira Riparia after First Moult 109
66. Moulting of Nephila Plumipes. From Wilder in
Proceedings American Association 111
67. Nephila Plumipes just after Moulting. From Wilder 111
THE STRUCTURE AND HABITS OF SPIDERS.
CHAPTER I.
ANATOMY AND CLASSIFICATION.
The spiders form a small and distinct group of animals, related to the
scorpions, the daddy-long-legs, and the mites, and less closely to the
insects and crabs. They are distinguished by the more complete
separation of the body into two parts; by their two-jointed mandibles,
discharging a poisonous secretion at the tip; and by their
spinning-organs, and habits of making cobwebs and silk cocoons for their
eggs.
The common round-web spider, _Epeira vulgaris_ of Hentz, will serve as
well as any species to show the anatomy of spiders in general. Fig. 1
shows the under side of this spider; Fig. 4, the upper side; and Fig.
5, an imaginary section through the body, to show the arrangement of
the internal organs. To begin with Fig. 1: the body is seen to be
divided into two parts, connected only by the narrow joint, A, just
behind the last pair of legs. The front half of the body, called
the thorax, contains the stomach, the central part of the nervous
system, and the large muscles which work the legs and jaws. The hinder
half, the abdomen, contains the intestine, the breathing-organs, the
principal circulating-vessels, the organs of reproduction, and the
spinning-organs. Connected with the thorax are six pairs of limbs, four
pairs of legs, B B B B, a pair of palpi, C, and a pair of mandibles, D.
[Illustration: Fig. 1.]
LEGS.
The legs are used chiefly for running, jumping, and climbing; but the
front pair serve often as feelers, being held up before the body while
the spider walks steadily enough on the other six. One or both of the
hinder legs are used to guide the thread in spinning; the spider at
the same time walking or climbing about with the other six or seven.
The legs are seven-jointed; and on the terminal joint are three claws,
Fig. 2, A, B, C, and various hair and spines. In many spiders a brush
of hairs takes the place of the middle claw, as in the jumping spiders,
Fig. 3. Spiders with these brushes on their feet can walk up a steep
surface, or under a horizontal one, better than those who have three
claws. The legs of most spiders have among the hairs movable spines,
which, when the spider is running about, extend outward at a right
angle with the leg, and, when it is resting, are closed down against
the skin.
[Illustration: Fig. 2.]
PALPI.
In front of the legs are the palpi, Fig. 1, C, C,—a smaller pair of
limbs, with six joints and only one claw or none. They are used as
feelers, and for handling food, and, in the males, carry the curious
palpal organs, which will be described farther on. The basal joints,
Fig. 1, E, of the palpi are flattened out, and serve as chewing-organs,
called “maxillæ.”
[Illustration: Fig. 3.]
Mr. Mason has lately described, in the Transactions of the
Entomological Society of London, a large spider which has teeth on
the inside of the palpi, which, when the spider is angry, are rubbed
against teeth on the mandibles, producing a noise.
MANDIBLES.
The front pair of limbs, the mandibles, Fig. 1, D, are two-jointed. The
basal joint is usually short and stout, and furnished on the inner side
with teeth and hairs. The terminal joint is a small and sharp claw,
which can be closed against the basal joint when not in use.
ABDOMEN.
On the under side of the abdomen, just behind the last pair of
legs, are two hard, smooth patches, which cover the front pair of
breathing-organs, the openings to which are two little slits at Fig.
1, H. Between these is the opening of the reproductive organs, and, in
female spiders, the epigynum, Fig. 1, J,—an apparatus for holding the
reproductive cells of the male.
At the end of the body are the spinnerets, which will be described in
another chapter. There are three pairs of them; but many spiders close
them together when not in use, so as to cover up the middle pair. The
third pair of spinnerets are often several-jointed, and extend out
behind the body like two tails. In front of the spinnerets is a little
opening, Fig. 1, K, which leads to air-tubes that give off branches to
different parts of the abdomen. At M, Fig. 1, are usually two colored
bands, or rows of spots, marking the course of muscles attached to the
skin at various points along these lines.
Fig. 4 is the back of the same spider. The head is not separated from
the rest of the body, as in insects, but forms, with the thorax,
one piece. On the front of the head are eight eyes, Q, which are
differently arranged in different spiders. At the back part of the
thorax is a groove, P, under which is attached a muscle for moving the
sucking-stomach, Fig. 5, _d_. From this point radiate shallow grooves,
that follow the divisions between the muscles of the legs. On the
abdomen are several pairs of dark smooth spots, which mark the ends of
muscles extending downward through the abdomen. The markings of this
spider are very complicated. The spot on the middle of the front of the
abdomen is a very common one, and, in some spiders, extends the whole
length of the body. The waved lines on each side are also common, and,
in long-bodied spiders, often form two bright-colored stripes, or rows
of spots, running nearly straight the whole length of the abdomen.
[Illustration: Fig. 4.]
INTESTINE.
Fig. 5 is a section of the same spider. The mouth is at _a b_, just
under and behind the mandibles, and between the maxillæ. It has an
upper, _a_, and under lip, _b_, each lined with a horny plate, in
the middle of which runs a groove. When the lips are closed, the two
grooves form a tube, which leads to the œsophagus, _c_, and so into
the stomach. At the end of the œsophagus is the sucking-stomach. This
consists of a flattened tube, to the top of which is attached a muscle,
_d_, connected with the groove in the back; and to the bottom, muscles,
_f_, attached to a tough diaphragm spreading across the thorax, and
fastened between the legs on each side at _g g_. When these muscles
contract, the top and bottom of the sucking-stomach are drawn apart,
and whatever is in the œsophagus sucked in. By this pumping motion
the spider is supposed to take liquid food from the mouth, and drive
it backward into the abdomen. Just behind the sucking-stomach, the
intestine gives off two branches, _e e_, which extend forward around
the stomach muscle, and meet over the mouth. Each of these branches
gives off on the outer side four smaller branches, _m m m m_, which
extend downward,—one in front of each leg,—and unite on the under side
of the thorax.
[Illustration: Fig. 5.
Section of a spider to show the arrangement of the internal organs:
_a_, _b_, upper and under lips of the mouth;
_c_, _c_, the œsophagus;
_d_, _f_, upper and under muscles of the sucking-stomach;
_e_, stomach; _g_, _g_, ligaments attached to diaphragm under the
stomach;
_J_, lower nervous ganglion; _k_, upper ganglion;
_l_, _l_, nerves to the legs and palpi; _m_, branches of the stomach;
_n_, poison-gland; _o_, intestine; _p_, heart; _R_, air-sac;
_S_, ovary; _t_, air-tube;
_u_, spinning-glands. ]
The intestine, _o_, continues backward through the abdomen to the
anus, in the little knob behind the spinnerete. The brown mass which
surrounds the intestine, and fills the abdomen above it, is supposed to
be a secreting-organ discharging into the intestine at several points.
HEART.
Over the intestine, and parallel with it, is the heart, _p_, a muscular
tube, with openings along the sides to receive the blood, and branches
through which it flows to different parts of the body. The greater part
of the blood enters at the front of the heart, and passes backward into
the abdomen, or forward into the thorax.
BREATHING-ORGANS.
In the front of the abdomen are the principal breathing-organs,—a
pair of sacs, R, containing a number of thin plates, through which the
blood passes on its way to the heart. Besides these, there is a pair of
branching air-tubes, _t_, opening near the spinnerets.
NERVOUS SYSTEM.
The nervous system has a large ganglion, J, in the thorax, from which
branches, _i_, pass to the limbs and abdomen. At the front end two
branches extend upward, each side of the œsophagus, to two smaller
ganglia, _k_, from which pass nerves to the mandibles and eyes.
The reproductive organs, S, lie along the under side of the abdomen,
and open between the two air-sacs.
The spinning-glands, _u_, lie above the spinnerets, and along the under
side of the abdomen. They will be more fully described in the chapter
on spinning.
POISON-GLANDS.
The poison-glands, _n_, are partly in the basal joints of the
mandibles, and partly in the head, and discharge by a tube which opens
at the point of the claw of the mandible, Fig. 15, _a_.
CLASSIFICATION.
There is not room in this book to explain the classification of spiders
into genera and species; but a description of the following well-marked
groups, which contain nine-tenths of all spiders, will give a general
idea of the differences among them, and help to understand what follows.
[Illustration: Fig. 6.]
MYGALIDÆ
This family includes the largest known spiders. The body is usually
very hairy and dark-colored. Most species have only four spinnerets;
and one pair of these are long, and are turned up behind the abdomen.
They have four air-sacs under the front of the abdomen, instead of
two, as other spiders. Their mandibles are very large, and work up and
down, instead of sidewise. The eyes are collected together on the
front of the head. They live only in warm countries. Specimens from
South America are exhibited in every natural history museum. Fig. 6
represents _Mygale Hentzii_, a species living in Arizona and Texas.
DYSDERIDÆ.
A small family of spiders with only six eyes. They have also four
breathing-holes in the front of the abdomen; but one pair leads to
branched tubes instead of sacs. They are usually found under stones,
with their legs drawn up close to their bodies, but can move very
quickly when so inclined. Very few species are known, and none are
common, in North America. Fig. 7 is _Dysdera interrita_ enlarged. Below
are the eyes as seen from in front.
DRASSIDÆ.
A large family of spiders, varying greatly in shape, color, and habits.
Most of them are dull colored, and live under stones, or in silk tubes
on plants, and make no webs for catching insects. Their eyes are small,
and arranged in two rows on the front of the head. Their feet have two
claws and a bunch of flat hairs. The spinnerets are usually long enough
to extend a little behind the abdomen. Fig. 8 is a _Drassus_, and the
eyes as seen from in front.
[Illustration: Fig. 7.]
[Illustration: Fig. 8.]
AGALENIDÆ.
Long-legged, brown spiders, with two spinnerets longer than the
others, and extending out behind the body. They make flat webs, with
a funnel-shaped tube at one side, Fig. 24, in which the spider waits.
Fig. 9 is _Agalena nævia_, the common grass spider.
[Illustration: Fig. 9.]
CINIFLONIDÆ.
A family resembling the last, but having peculiar spinning-organs,
which will be described farther on, Fig. 35.
LYCOSIDÆ.
The running spiders. Very active spiders, living in open places, and
catching their prey without webs. Their legs are long, the hind pair
being the longest. The head is high, and the arrangement of the eyes
peculiar to the family, Fig. 10.
[Illustration: Fig. 10.]
ATTIDÆ.
The jumping spiders. The body is usually short, and the head square.
The arrangement of the eyes is characteristic, Fig. 11, _a_. The two
large ones in the middle give these spiders a more animated look than
those of other families. The legs are short, and the front pair often
stouter than the others. They can walk easily backwards or sidewise,
and jump a long distance. Fig. 11 is the common gray jumping spider
enlarged.
[Illustration: Fig. 11.]
[Illustration: Fig. 11 _a_.]
THOMISIDÆ.
The crab spiders. The body is usually flat, and wide behind. The front
two pair of legs are longer than the others, and so bent that the
spider can use them when in a narrow crack. Some of them, like crabs,
walk better sidewise than forwards. Like the running and jumping
spiders, they make no webs for catching food. The eyes are small, and
simply arranged in two rows, Fig. 12.
[Illustration: Fig. 12.]
THERIDIIDÆ.
The largest family of spiders. Most of them are small, with large
rounded abdomens and slender legs. They live usually upside down,
holding by their feet under their webs. They make large cobwebs of
different shapes for different species, and depend for food on what is
caught in them. To this group belongs the genus _Erigone_, containing a
great number of the smallest spiders known. Fig. 13 is the common house
_Theridion_ enlarged.
[Illustration: Fig. 13.]
EPEIRIDÆ.
The round-web spiders. Large spiders, with flat heads, and eyes wide
apart, and short, round abdomens, Figs. 1, 4. They make webs formed
of radiating lines crossed by other adhesive ones in a spiral or
concentric loops, Fig. 28. They hang in the web, head downward, or live
upside down in a hole near by.