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COLLECTING SPECIMENS
I must say before proceeding that there are many different methods available
for collecting pseudoscorpions and each should be used according to the case.
Collecting of large pseudoscorpions, especially
those belonging to the suborder Monosphyronida, may be done by hand from the bark of trees and logs or by sifting soil, debris,
and rotten wood. However, collecting of most pseudoscorpions in this ways is
laborious and slow because of the low population density of some species and because of the small size, seclusive habits,
and light color of other species, especially those of the suborder Heterosphyronida and Diplosphyronida.
The most efficient method for collecting pseudoscorpions
is by the use of the Berlese funnels, named after the Italian entomologist Berlese, who first used them extensively. A Berlese funnel is a very simple apparatus, consisting of a fairly long funnel suspended
wide end up, with a screen placed about a third of the way down the funnel, with heat applied either around the upper portion
of the funnel or over the top of the funnel, and with a container of preservative, preferably 80-85 % ethyl alcohol, around
the small bottom opening. Leaf mold, bark scrapings, broken-up rotten wood, and
other material suspected of harboring pseudoscorpions is placed on the screen, the heat source is turned on, and after a day
or so the pseudoscorpions leave the dried sample and migrate downward, dropping into the preservative.
A funnel very satisfactory is 15 in. from top
to bottom and the top has a diameter of 12 in. The bottom opening, exactly seven-eights
in. in diameter, fits into a half-pint cream bottle, which makes an ideal container for the preservative. Three angle brackets or hangers are soldered inside the funnel to provide a support for the screen, which
is made of a quarter in. or eight in. mesh hardware cloth; the mesh used depends upon the type of sample. A battery of several funnels in a rack will allow the collector to sample a hundred pounds or more of material
in one operation.
Samples of leaf mold or other material are brought
into the laboratory in cloth bags. Before being put in the funnel, each sample
is sifted carefully through a screen sieve of half-inch mesh. Clumps of moss,
leaves, sob, and pieces of wood or bark are torn up by hand into small fragments as they are put into the sieve; then this
material is racked over the sieve and shaken, the sifted material being collected on a cloth or paper.
Pieces of wood or bark are knocked sharply against
each other to dislodge any animals that might cling to them. The sifted material
is then placed on the screen in the funnel and piled up around the sides to leave a small open space in the center of the
screen. This central opening allows the easy migration of animals in the upper
part of the sample down into the bottom part of the funnel. The funnel so loaded
is then placed in the rack for support, the bottle with preservative is placed under the narrow end, and heat is applied.
If steam is used as a source of heat, the small
cooper lines that conduct it act as a partial support for the funnel by encircling it about half way between the screen and
the top; a piece of cloth is tied tightly over the top of the funnel. If an electric
light or a choke coil is used for heating, it should be hung directly over the center of the funnel and no cloth tied over
the top. With a light or choke coil, it is often well to use a wide reflector
that approximates in diameter to the top of the funnel.
Care must be taken not to heat the sample too
rapidly. Otherwise, moisture will condense in the lower part of the funnel and
trap many of the animals working their way toward the bottom, or the heat may kill many of the organisms before they have
an opportunity to move out of the sifted material. A little experience furnishes
the best gauge of the intensity of heat to be used. An application of heat sufficient
to dry the sample in 4 or 5 days is usually satisfactory. As the sample dries,
the organisms move out and downward, and finally drop into the bottle of preservative.
The Berlese funnel is extremely useful for collecting
many animals in addition to pseudoscorpions: groups of beetles, particularly Staphylinidae, thrips, Collembola, many groups
of parasitic Hymenoptera, ants, millipedes, and centipedes, and a wide range of other minute animals that live in soil, surface
cover, logs, or bark.
Samples for the Berlese funnel may be collected
at any time of the year. If collected during the warm months, they should be
brought to the laboratory and placed in the funnels within a day or two; otherwise considerable loss of population occurs
within the samples. If collected during the cold months, they may be kept in
cold storage for a week or two with little loss.
The following suggestions may prove helpful in
picking up samples. For leaf mold samples, scrape off and discard the dry surface
leaves and scoop up the lower, rotted layers of leaves together with an inch or two of the adjacent soil. You may encounter especially good samples where leaves have blown in along the edge of a log. In such a situation, take some of the log bark with the sample. Collect
rotten log samples in large hunks and break them up in the sieve. From either standing stumps or fallen logs in which the wood is still too hard to break up, collect the
loose bark, as it is often quite productive. Frequently if you roll a log over,
you may find animal runs under it; the debris and earth under and around these runs, together with animal nests, frequently
give unusual catches.
Probably the most productive single type of sample
is that taken from the interior of a standing hollow tree. At the bottom of the
hollow you may find a foot or more of fine, rotten, woody material that you can scoop out by reaching through a break in the
base of the tree. A 50 or 60-puond sample of this is almost sure to net many
interesting forms. Occasionally you may collect a wet sample, such as sod from
a marsh or debris from a stream edge. If you allow it to remain in the sack for
a few days it will usually dry out enough to permit sifting. Allow winter samples
to thaw and dry before you sift them.
FEEDING HABITS
Pseudoscorpions feed on small animals such as mites, ants, and a wide variety of other insects, as indicated by the
many pseudoscorpions observed with such prey in the chelae of the pedipalpi or palps.
The pseudoscorpions mouth, located on a tubular structure called the rostrum, contains a sucking structure, the pharyngeal
pump, for taking the liquid food. The pseudoscorpion grasps its prey with the
palps. These prehensile organs are supplied with a venom apparatus that effectively
kills or anesthetizes the captured prey within a matter of seconds. The palps
and chelicerae, together or singly, hold the prey to the mouth and the pseudoscorpion sucks the fluids from the body of its
victim.
The larger pseudoscorpions, especially Chelifer cancroides, make interesting pets. One may be kept in a small corked vial into which is released a fly occasionally. The pseudoscorpion will stack the fly patiently for a long time; the suddenly it will reach out a palp
and seize the fly. A good-size house fly will put up quite a struggle, sometimes
flying around with the pseudoscorpion attached; sometimes the pseudoscorpion will be stretched out in mid air, grasping the
cork with one chela and the fly with the other; but in a few moments the battle is over, and the fly is completely quiet. Then the feast begins.
Evidence to date indicates that no pseudoscorpions live as ectoparasites on larger animals. Pseudoscorpions occur abundantly in mammal and bird nests, but apparently they are not parasitic on the
mammals or birds but instead feed on small arthropods in the nests. Species have
been reported as nipping man, but without inflicting any appreciable injury.
Large numbers of species have been reported from beneath the elytra of beetles, as well as from the bodies of other
insects and birds, as described by Vachon. These cases appear to be nothing more
than phoresy, with the pseudoscorpions feeding on mites and other soft bodied arthropods associated with the larger flying
insects and birds. Vachon forcefully expresses the idea that phoresy with few
exceptions is confined to the females. He believes that phoresy is a response
to insufficient food at a time when the females are carrying and feeding the larval young.
ENEMIES
While the pseudoscorpions prey upon smaller animals, they are in turn the prey of larger animals, especially birds,
as indicated by the frequency with which pseudoscorpion remains are recovered from the digestive tracts of birds. The part played in food cycles appear to be the pseudoscorpions claim to ecological importance.
DEVELOPMENT
Pseudoscorpions have several
distinct stages in their life history: (1) the egg, in most species carried by the female; (2) the larva, in most species
also carried by the female; (3) three stages of nymphs, which are free living; and (4) the adult.
The pseudoscorpion female usually produces only a small number of eggs, ranging from 3 or 4 to as many as 30. The eggs in most species are not laid indiscriminately, but are simply extruded from
the abdomen and retained as a group attached to the base of the abdomen in contact with the external genitalia. As the eggs are laid, they are grouped in a single-layered rosette or around the periphery of a spherical
mass. In either case the egg mass becomes enclosed by a this membrane.
As young develop within the eggs, the enveloping membrane is lost and the larvae assume positions with their heads
toward the center of the rosette or spherical mass. Each of the first stage larvae
has a sucking apparatus for feeding, and rudiments of the appendages, nerve ganglia, and other structures. The larvae secure a nutrient fluid secreted from the maternal ovaries, which become modified fro this particular
function. During the period of larval development, the females of those groups
in which the larvae from a single layered rosette remain active, while the females in which the larvae are arranged in the
form of a spherical mass have been observed to seal themselves in a nest and remain inactive.
The presence of large amounts of yolk in the eggs of a few species suggests that the larvae in these groups develop
without attachment to the mother.
As development continues, a second larval stage is formed. In this stage,
the sucking apparatus is atrophied and the larva apparently lives on the food accumulated during the first or feeding stage
of larval development. Also, during the second larval stage, the appendages and
other structures of the nymph gradually make their appearance.
At the end of the larval development, the first nymphal stage or protonymph escapes from the brood pouch and begin
to lead an independent life. The protonymph has essentially the same general
appearance as the adult. The continued development includes three molts, and
the individual passes successively through the protonymph, deutonymph, and tritonymph stages, to form finally
the sexually mature adult stage. At the time of each molt, the nymph secludes
itself in a silken nest for a period of 10 or 15 days, during which time distinct morphological reorganizations take place. The various morphological changes that occur between nymphal stages and between the
tritonymph adult include the gradual addition of tactile setae on the palpal chelae and a gradual change in the shape of various
body parts, such as the segments or podomeres of the appendages.
MATURITY AND REPRODUCTION
Adult pseudoscorpions are undoubtedly fairly long lived, living probably for six months to a year or two. This surmise is based on collecting observations and notes made on a few individual kept in captivity. Few exact data over an extended period are available.
As is true of their relatives, pseudoscorpions
are dioecious. The males and females are similar in appearance. With the possible exceptions of a few forms, such as the genus Microbisium, in which the males have
never been found, they reproduce sexually; apparently in the Microbisium females reproduce parthenogenetically.
According to Beier, mating takes place in the
spring, during April and May, but this information is based on the study of only a few forms in the holarctic regions and
possibly cannot be applied to species from other areas. Unfortunately, information
relative to mating is from observations of a few species of Monosphyronida only, and generalizations cannot be made for the
entire order. In the few species that have received detailed study, the male
and female perform a courtship dance as a part of the mating activity. During
the period of marked sexual activity and the courtship dance, a spermatophore is released by the male. Sperms from this spermatophore are picked up by the female. About
1 month after the transfer of sperm from the male to the female, the eggs are extruded.
HABITAT PREFERENCES
Pseudoscorpions have invaded many different habitats in almost every part of the world.
For the most part, the smaller forms live in debris and fertile soil, the larger forms under stones, under bark of
trees, in decaying vegetation, and abundantly in mammal and birds nests. One
genus, Garypus, is found usually along the seacoast under stones and among algae and seaweeds. Some species of pseudoscorpions occupy very particular and restricted niches. Different habitats
are: deciduous forests (ground cover and litter, rotting wood or under bark); rock outcrops (debris and leaf mold); sand dunes
(grass and ground cover); in swamps and bogs (moss and debris in bogs); domestic situations.
PREPARATION OF MATERIAL
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