Hair Spider
(Arachnis imitatis hairii)
guide to identification and zoological analysis


Scientific Name

Arachnis imitatis hairii

Common Names
Zoological Classification

The table below shows the complete zoological classification for this organism...

 Zoological Classification Table 
PHYLUM Arthropoda
SUBPHYLUM Chelicerata
CLASS Arachnida
ORDER Araneae
SUB-ORDER Araneomorpha
FAMILY Pholcidae
GENUS Arachnis
SPECIES imitatis


A. imitatis hairii has been found to occur in all parts of the world where human habitation is present. Incidence has been observed to be higher amongst human populations where cultural mores predispose towards longer scalpal hair. Other possible subspecies - that may form associations with other long-haired animal species - have not yet been identified, although it is generally believed amongst zoologists that such subspecies are likely to exist.


Irregular Morphology

A. imitatis hairii is unique amonst all species of spiders in its ability to develop an arbitrary number of legs. Notably, its legs are also found to be undifferentiated, lacking the coxa, trochanter, femur, patella, tibia, metatarsus, and tarsus segments universally found amongst other spider species.

Moreover, other dramatic anatomical variances amongst individuals have also been observed. In fact, early zoologists to study this species postulated that it was - in fact - not a true spider, hence its scientific name. Compliance with general parameters of arachnidian anatomical layout seems to occur, however, with discrete cephalothoraxic, foveal, and abdominal regions being distinctly identifiable in the majority of observed specimens.


The photographs below show an exemplary specimen of this species, captured from two different angles (click on the pictures for a larger view).

Angle 1
Angle 2

Notice how the pedicel (the stalk that connects the major anterior and posterior regions of the spider's anatomy) is particularly pronounced in this specimen. On close inspection you may also be able to notice, at the abdominal posterior, the poorly developed false spinnerets that are indicative of this species. Through millions of years of evolution and tight association with its host species, the spinnerets of A. imitatis hairii have evolved to become nonfunctional. Relying on the scalpal hair of its host for the formation of nests and other structures, this species no longer has the need for the spinning of webs.

Life Cycle

Embryonic Stage

Hair spider eggs are hatched in a special nest formed by the male adult. Very early nymphs are - for a brief period - acclimatized to an environment of human hair before making their long and fateful journey towards instruments - such as brushes and combs - that might facilitate their transfer to the hair of a human host.

Larval Stage

A. imitatis hairii exhibits distinctly parasitic behavior, spending much of its life cycle associated with a human host, almost exclusively habitating the periscalpal region. Parasitization by this species usually does not present with deleterious effects. In fact, in its early stages this species is virtually indistinguishable from its host environment.

Pupal Stage

Much like members of the order Lepidoptera, A. imitatis hairii undergoes a metamorphosis in the course of its life cycle. After some time spent in a larval stage during which active growth occurs, the individual then enters a pupal stage in which it appears externally dormant, but during which time it is undergoing significant structural changes. Through a cleverly camouflaged pupal case, the hair spider in this stage is usually able to elude detection. In some cases, however, the pupa may be suspected of being a hair knot and may be prematurely expelled by its host through vigorous brushing action. The mortality rate for hair spider pupae expelled in this manner is exceptionally high.

Adult Stage

While spending its larval and pupal stages being virtually indistinguishable from the scalpal hair of its host, it is on separation from its human host that the hair spider takes on its unique adult form. Emergence of the mature adult from the pupal cocoon occurs with detachment from the host and is often accompanied by a sharp painful sensation being experienced by the host. Interestingly, it is often the same instrument that is responsible for infection of the host - the hair brush or comb - that is also responsible for triggering the emergence of the adult hair spider from its pupal case.

Reproductive Behavior

Mating Ritual

As is the case with many other species of the animal kingdom, the male hair spider adult is typically larger than its female counterpart. More than the size of the individual, though, the size of the nest is what plays a central role in determining which male the female will choose to mate with (see the subsection "Nesting Habits" below).

In the exclusive photographic footage shown below, the rare mating act of this species is captured for the first time...

Sighting of Female
Male Approaches
Contact is Made
Female Turns to Present
Copulation Occurs

Initially, the male adult sights the potential female mate. After the female has signalled approval to the male, the male slowly and cautiously approaches. Eventually, after a few moments the two make close contact. At this stage, an intricate interplay occurs as the male and female make physical contact using their antennae, seemingly communicating to one another. Finally, the female turns to present. Now given access, the male proceeds to mount the female and copulation occurs. Within minutes the entire act is complete.

It should be pointed out that the female of this species is primarily an egg production "factory". The egg sack that is produced by the female, while tiny, may contain hundreds of eggs. The act of copulation results in these eggs being fertilized. On completion of the copulatory act, the egg sack is transferred from the female to the male, by way of a sticky glue that is secreted from the abdomen of the male. So it is the male, in fact, that will carry the fertilized egg sack back to the nest where it will be protected until hatching occurs.

Nesting Habits

Spending its early developmental stages attached to the hair of its human host, A. imitatis hairii exhibits a continued affinity with human hair throughout the remaining adult stage of its life cycle. This species exhibits what can best be described as a hoarding behavior with regards to hair shed from its human host. Once detachment has occured, the adult individual engages in a gathering practice. Loose bundles of hair often found to collect in the corners of bathrooms are thought to be the result of this gathering and hoarding. Left undisturbed, these hair bundles will eventually be formed into nests by the adult hair spider, as shown in the photographs below...

Nest in Early Stage
Mature Nest

From these pictures you'll notice that it is the male hair spider that is responsible for tending to the nest. In fact, nest size appears to play an integral role in the mating ritual of this species, with the diminutuve female typically favoring the male that has assembled the largest nest. It is in this nest that the egg sack will be nurtured and protected from other predatory spider species. Upon hatching, the hair spider young will nestle amongst the many hairs that make up the nest, thereby preparing them for the host environment in which they will spend the major portion of their life cycle.

Public Health Impact

Symptoms of Infestation

Due to the highly effective way in which this species blends into its host environment, infestation by this species is generally asymptomatic. It is often only possible to predict the presence of an infestation by the observation of associated conditions that are known to predispose to susceptibility. For example, individuals with longer unkempt scalpal hair have been found to be more susceptible to infestations. The largely cosmetic condition commonly known as "split ends" has also been found to be associated with an increased risk of infestation.

Since this species inhabits scalpal hair, infestation by this species is virtually unheard of in individuals suffering from the condition of alopecia. Cultural factors have also been been found to play a role in the prevalence of A. imitatis hairii infestation, with statistically significant differences being observed between racial groups predisposed to long straight hair versus racial groups predisposed to short curly hair. Specifically, this species has not been seen to present significantly amongst individuals of African descent.


A. imitatis hairii has been observed to form a tight bond with a specific individual host. Often, many generations of the same family will complete their life cycles on the same host. Because of this, infestation by this species is believed to not be transmissable - even in situations of intimate personal contact between individuals, such as pillow swapping while sleeping in the same bed or sharing the use of a hair brush or comb.

A. imitatis hairii is, therefore, not thought to present a significant public health risk. There is even some speculation amongst alernative / holistic medicine practitioners that this species is a natural, healthy, and necessary foreign organism in the human species, much like the various bacteria and fungi that make up the flora and fauna of the human gastro intestinal system.