Amaurobioidea: Rummaging through a Wastebasket

A representative of the strikingly-coloured Nicodamidae from Australia. Photo by Nick Monaghan. While such spiders were previously identified as Nicodamus bicolor, there are no less than 23 species in seven genera that have previously been included under that name.

One term that you may come across in discussions of phylogeny is the concept of a "wastebasket" taxon. As the name suggests, a wastebasket taxon is one into which authors tend to throw everything that they can't really deal with. Often, a wastebasket will include the members of a group that are relatively unspecialised, often primitive, and united less by their shared characters than their lack of distinct features to connect them to one or another of the specialised subgroups that the author may recognise within the parent group. Phalangodidae among short-legged harvestmen, Sylviidae among passerine birds and Perciformes among spiny-finned fishes are all examples of taxa that have become wastebaskets in the past. Some wastebasket taxa are explicitly established as such, like the 'Deuteromycota' that included asexual fungi before techniques were developed that made it significantly easier to relate asexual and sexual fungal taxa. More often, though, a taxon originally based on a certain combination of features will develop into a wastebasket over time as phylogenetic studies show that the original basis characters for that taxon represent plesiomorphies (ancestral characters). This week's highlight taxon, the spider superfamily Amaurobioidea, perhaps belongs to the latter group.


Tegenaria gigantea (Agelenidae). Photo from Wikipedia. Agelenids build funnel-shaped webs and are apparently often called some variant of "funnel spiders" in North America, but such names are likely to cause confusion here in Australia with a certain notorious mygalomorphs. Some species of Tegenaria such as the hobo spider are also known for being toxic, but nowhere near as toxic as the Australian funnel-web.

In an earlier post, I included a quick overview of basal spider phylogeny, going as far down as the clade Araneoclada that unites those spiders that have only a single pair of book lungs (ancestrally, at least - many families of Araneoclada have lost the book lungs entirely, or evolved tracheae in their place). Members of the Araneoclada are further divided between the Haplogynae and the Entelegynae, originally based on the presence (Entelegynae) or absence (Haplogynae) in females of paired copulatory ducts opening on a sclerotised plate called the epigyne. While the absence of such ducts in the Haplogynae is obviously a primitive character and no longer regarded as uniting them, the group has funnily enough been supported as monophyletic based on a number of other characters (except for a small number of 'haplogyne' taxa that are phylogenetically entelegynes) (Coddington & Levi, 1991). However, the Amaurobioidea belong to the Entelegynae, which is by far the larger of the two clades. Within the Entelegynae, the primary division was long based on whether or not a species possessed a cribellum, a plate-like structure among the spinnerets that bears hundreds of tiny silk-producing spigots. As these spigots exude silk simultaneously, the spider uses a specialised arrangement of bristles on the fourth pair of legs to weave them together to form a woolly thread (see here for a more detailed description). Because this woolly thread is composed of multiple tangled strands, it can effectively entangle prey such as small insects that get caught among the strands. Unfortunately, as knowledge of entelegyne spiders improved it became clear that possession of a cribellum did not define a phylogenetically coherent group. A number of cases were identified of pairs of taxa clearly related by other characters in which one taxon possessed a cribellum and the other did not. The eventual conclusion was that the cribellum was an ancestral character for the Entelegynae (as also supported by its presence in one haplogyne family, the Filistatidae) that had been lost on numerous occassions.


Ctenus floweri (Ctenidae), from Singapore. Photo by David Court. Ctenids are active hunters.

In general, the Amaurobioidea included cribellate spiders with unbranched abdominal median tracheae, as opposed to Dictynoidea with branched abdominal median tracheae (Coddington & Levi, 1991). Families that have been assigned to Amaurobioidea include (among others) Amaurobiidae, Agelenidae, Ctenidae, Amphinectidae and Nicodamidae, but relatively little unites these families. Most of them are generally ground-dwellers (which may explain the common name of one of the best-known members, the hobo spider Tegenaria agrestis). Many members build small sheet-webs, but others are active hunters. Both the characters referred to above have since been shown to represent plesiomorphies of larger clades, with the alternative conditions arising multiple times. The phylogenetic analysis of entelegyne spiders by Griswold et al. (1999) found the 'Amaurobioidea' to fall within a clade that was sister to the clade including the orb-weavers, but the same clade included the Dictynoidea and Lycosoidea (wolf spiders and such) nested within 'amaurobioids'. Indeed, not even the type family of Amaurobiidae was monophyletic, with some members closer to the lycosoids while others were closer to the agelenoids. The Amaurobioidea, it seems, was a bust.

Coming up - science and art, whether taxonomy is science, why family names are so awful, micro-spiders, and Parapseudoleptomesochrella almoravidensis.

REFERENCES

Coddington, J. A., & H. W. Levi. 1991. Systematics and evolution of spiders (Araneae). Annual Review of Ecology and Systematics 22: 565-592.

Griswold, C. E., J. A. Coddington, N. I. Platnick & R. R. Forster. 1999. Towards a phylogeny of entelegyne spiders (Araneae, Araneomorphae, Entelegynae). Journal of Arachnology 27: 53-63.

Araneidae - With Web and With Scent

The St. Andrew's Cross (Argiope keyserlingi). Photo by Louise Docker.

The orb-weavers are undoubtedly the best-known of all spiders. Ask anyone to imagine a spider and they will probably picture an orb-weaver (they may also have transcribed the words "some pig" in the web). This is something of an unfair characterisation - of the more than 100 recognised families of spiders, less than ten are orb-weavers. Still, it is one of the orb-weaving genera that holds the name of "spider", Araneus, which, as the only generic name used in Clerck's (1757) Aranei Svecici, the only taxonomic work recognised by the ICZN that predates the 1758 tenth edition of Linnaeus' Systema Naturae, is officially the oldest generic name in zoological nomenclature*. That's right - spiders came before humans. Nyeh nyeh nyeh.

*Admittedly Clerck did use the name Araneus for all spiders, not just species included in the modern Araneus.

The Araneidae are the largest family of orb-weaving spiders, with a little less than 3000 described species. They are actually a lot more numerous than you might realise - many species build their webs only at night, taking them down in the morning before hiding during the day and rebuilding the web every evening. The family is decidedly diverse in appearance - from the gaudy colours and spines of the Christmas spiders to the idiosyncratic figures of the tailed spiders to one group whose common name describes their appearance perfectly - the bird-dropping spiders.



The classic orb-web is made by first floating a line of sticky silk horizontally across a space between two anhoring points (such as a pair of branches), then running a second looser non-sticky strand along the initial strand. The spider then drops herself* from the centre-point of the second strand, trailing a third strand behind her, so that the second and third strands form a Y-shape. The vertex of the Y will be the centre of the web. The spider next constructs an outer frame, as shown above in a diagram by Ed Nieuwenhuys (the page linked to has diagrams of each of the stages in orb-web construction), then runs a series of spokes from the centre of the web to the outside. She then runs a broad spiral of non-sticky thread from the centre of the web until she reaches the outer edge. After that, it travels back to the centre laying a much tighter spiral of sticky thread, removing the non-sticky scaffold as she goes. As the sticky thread is stretched, the sticky coating breaks into a series of globules of coiled thread, which is how the web is able to be so elastic and stand up to the thrashings of captured prey. The spider herself is able to move about without being trapped by means of secretions produced by glands near the mouth with which she coats her legs. Forster & Forster (1999) refer to an experiment where the tips of a spider's legs were dipped in solvent before the spider was returned to its web. The spider initially showed great difficulty in moving due to the removal of its protective coating, though it was able to renew the covering and regain mobility. After the web has been completed, the spider will take up residence at the central hub, legs resting on the radiating spokes in order to feel for any vibrations. Araneid eyesight is almost non-existent, and orb-weavers are incapable of hunting without a web. They are perhaps the closest thing to a terrestrial filter-feeder, filtering the air for small animals.

*All spiders are referred to as female unless proven otherwise, like ships and birds of prey. It's another one of those things that make the English language so damn confusing.


An unidentified member of the genus Gasteracantha. These spiders come in a dazzling array of colours and ornamentations, and unlike many other araneids are often visible during the day, earning them such names as "jewel spider" or "Christmas spider". Colour patterns can vary significantly even between members of the same species. Photo from here.

Many araneids may vary the basic orb-web design further. Ladder-web spiders, for instance, have a long narrow web instead of the usual circle. The function of these is not really understood, though it has been suggested as a specialisation for catching moths - moths have a covering of loose scales on their wings which would normally allow them to shake off a web and escape, but it is suggested that the elongate shape of a ladder-web means that as the moth shakes off its scales, it falls onto a lower part of the web until eventually it is no longer able to escape. Many orb-weavers construct a stabilimentum, a zig-zag ladder-shaped structure that extends upwards from the central hub. Again, despite being such a distinctive structure, the function of the stabilimentum remains largely unknown, though subject to intense debate - suggested roles include strengthening the web (the original source of the name), disguising the position of the spider from predators or making the spider look bigger, attracting prey or even making the web more visible for larger animals and so reducing the risk of them walking or flying through it. One large and striking araneid found here in Australia, the St. Andrew's cross (Argiope keyserlingi), shown at the top of this post, gets its name because it builds four stabilimenta radiating from the central hub, while the spider itself sits with the front two and rear two pairs of legs held alongside each other, so the spider itself forms the eponymous cross shape.

Perhaps the most remarkable thing about araneids, however, is that despite the total dependence of most species on their webs for survival, some species no longer make them. The aforementioned bird-dropping spider (Celaenia) is so-called because its lumpy brown-and-white-splotched abdomen really does look like a lump of bird poo, offering excellent camouflage from discerning predators. Instead of constructing a full web, Celaenia simply hang from a leaf or a thread with their legs outstreched. There they catch and feed on moths (excellent pictures of hunting Celaenia can be seen at Esperance Blog). It used to be a mystery how this seemingly limited and haphazard means of capture could possibly feed the spider (after all, how many moths could reasonably be expected to pass by one point over the course of a night) until it was observed that a surprising proportion of the moths being caught (that is, all of them) were males, and that, far from passing by the spider accidentally, male moths will actually approach the spider and remain close by it until caught. It seems that the spider actually emits pheromones that mimic those of a female moth, luring their prey in with the false promise of sexual gratification (like a Trojan virus attached to a spam e-mail). The bolas spiders of the tribe Mastophoreae have refined this process further - as well as producing attractive pheromones, they also dangle a single sticky thread below themselves. When a moth approaches close enough, the spider spins the sticky thread around in the air until it sticks to the moth and they are able to draw it in. How bird-dropping and bolas spiders make their living until they become large enough to handle moths seems a little confused - Brunet (1996) claims that Celaenia construct standard orb-webs until they reach maturity, while bolas spiders produce different pheromones for attracting different-sized moths when at different ages. Forster & Forster (1999) and Yeargan (1994), in contrast, both claim that Celaenia spiderlings produce pheromones to attract psychodid midges. Interestingly, while bird-dropping and bolas spiders are both members of the subfamily Araneinae, it is debatable whether they are each other's closest relatives within the subfamily (Yeargan, 1994), so it is possible that their amazing pheromone-capture techniques could have arisen separately of each other!

REFERENCES

Brunet, B. 1996. Spiderwatch: A Guide to Australian Spiders. Reed New Holland: Sydney.

Forster, R. R., L. M. Forster. 1999. Spiders of New Zealand and their Worldwide Kin. University of Otago Press: Dunedin (New Zealand), and Otago Museum: Dunedin.

Yeargan, K. V. 1994. Biology of bolas spiders. Annual Review of Entomology 39: 81-99.

Spiders Losing their Lungs

Hypochilus petrunkevitchi - photo by Marshal Hedin from Wikipedia.

The current Taxon of the Week arguably has a pretty poor claim on the title, because it is no longer recognised as a valid taxonomic grouping. As I have explained before, modern spiders can be divided into three suborders or infraorders or what-have-you. The Mesothelae or Liphistiomorphae (segmented spiders) are a small group distinguishable from all other spiders by their obviously segmented abdomens. The Mygalomorphae (vertical-fanged spiders) have fangs that move straight up and down, and include the trapdoor and funnel-web spiders and American tarantulas. The largest group of spiders by far is the Araneomorphae (cross-fanged spiders), with fangs angled towards each other, including orb-weavers, cobweb spiders, jumping spiders, wolf spiders, and pretty much any other spider family you're likely to be familiar with. However, some older references may list a fourth group, the Hypochilomorphae, and it's with the latter that we're dealing today.


The Tasmanian cave-dwelling austrochilid Hickmania troglodytes. The four yellow spots visible on the underside correspond to the positions of the book lungs. Photo by Niall Doran from here.

The 'hypochilomorphs' include three small families, the Hypochilidae, Austrochilidae and Gradungulidae, that are now regarded as basal members of the Araneomorphae. Like other araneomorphs, they possess fangs that are angled towards each other rather than parallel. Where they differ from other araneomorphs is in the number of book lungs they possess. Book lungs are the ancestral respiratory structure for all arachnids, and evolved from the gills of their aquatic ancestors as they adapted to life on land. They are little more than gills recessed into the underside of the animal and covered over to prevent moisture loss, and the name "book lung" refers to their appearance in cross-section like leaves of a book. The ancestral number of book lungs in arachnids is four, though many arachnids (particularly the smaller forms, and including some spiders) have independently replaced the book lungs with tracheae, or lack any specialised respiratory structures entirely. Most araneomorphs with book lungs have lost the posterior pair and only have two book lungs. Hypochilomorphs retain the posterior pair, demonstrating their basal position to other araneomorphs and causing them to all too often be damned with the execrable title of "living fossil". However, because this is an ancestral feature rather than a derived one, it does not indicate that hypochilomorphs form a group exclusive of other araneomorphs, and other features make it clear that Austrochiloidea (Grandungulidae and Austrochilidae) are more closely related to the other araneomorphs than they are to Hypochilidae (Griswold et al., 1999). The remaining araneomorphs have usually been presented as a single clade (the Araneoclada), though at least one species of Filistatidae, Kukulcania hibernalis, possesses posterior book lungs as a juvenile, suggesting that family lost the posterior book lungs independently of other araneomorphs, and Lopardo et al. (2004) suggested that Filistatidae may be outside the Austrochiloidea + Araneoclada clade.

The Hypochilidae are large spiders found in Asia and North America. They construct a unique web for snaring prey, often referred to as a "lampshade web" in reference to its shape, though if the description in Forster & Forster (1999) holds for all hypochilids, then the photo on the Wikipedia page for this family is quite possibly upside down. According to Forster & Forster, Hypochilus builds its web on the underside of an overhanging rock, with a tightly woven upper section flaring out around the lower circular edge. Hypochilids are mostly montane species.



The Austrochiloidea are restricted to Southern Hemisphere continents - the Austrochilidae are found in southern South America and Tasmania, while the Gradungulidae are found in eastern Australia and the South Island of New Zealand (Forster & Forster, 1999). The Austrochilidae build large horizontal webs, but many Grandungulidae have abandoned web-building and become active hunters. The Gradungulidae are characterised by the significant increase in size of one of the claws on the legs, which is used to great effect in seizing prey. In one of the Australian web-building species, the cave-dwelling Progradungula carraiensis, a long, sparse web is built between the ground and an overhang, up to and exceeding a metre in height. The spider itself sits head downwards at the base of the web, low enough that the front legs are near the ground. Any suitable prey that walks by the spider is grabbed with the front legs and bitten. The prey may be eaten where it is caught, or carried up to the top part of the web that also serves as a retreat for the spider. One of the New Zealand species, Pianoa isolata, has abandoned the web but hangs down among strands of dense moss, catching its prey in a similar manner to Progradungula. A New Zealand cave-dwelling species, Spelungula cavernicola, shown above in a photo by Paddy Ryan, is an active hunter but often feeds on its prey suspended in mid-air from a silk dragline. The round egg-sacs are also hung from draglines, probably as protection from potential predators.

REFERENCES

Forster, R. R., & L. M. Forster. 1999. Spiders of New Zealand and their Worldwide Kin. University of Otago Press: Dunedin (New Zealand), and Otago Museum: Dunedin.

Griswold, C. E., J. A. Coddington, N. I. Platnick & R. R. Forster. 1999. Towards a phylogeny of entelegyne spiders (Araneae, Araneomorphae, Entelegynae). Journal of Arachnology 27: 53-63.

Lopardo, L., M. J. Ramírez, C. Grismado & L. A. Compagnucci. 2004. Web building behavior and the phylogeny of austrochiline spiders. Journal of Arachnology 32: 42-54.

Tarantulas sans Tarantella

It's interesting how different people perceive levels of risk. Someone once asked how I could be completely unafraid of spiders, but be extremely nervous around cars (I am - a friend of mine once banned me from riding in the passenger seat when she was driving, because the sight of my knuckles turning white as I gripped onto the handlebar would make her nervous). I asked him in return how I could possibly be otherwise - hardly anyone is ever seriously hurt by a spider, but cars kill large numbers of people on a regular basis. The point of that little anecdote, in case you were wondering, is to introduce a family of spiders that have provided stock horror film fodder for years, but are widely known to be fairly harmless - the Theraphosidae.



Theraphosidae are a family of large spiders found mostly in ex-Gondwanan landmasses - South America, Africa, India and Australia, as well as in south-east Asia. These are the spiders best known as bird-eating spiders or tarantulas, though the name "tarantula" originally applied to a member of a quite different family of spiders, the European wolf spider Lycosa tarantula. The photo at the top of the post (from here) shows an Australian species of Selenocosmia. The photo just above this paragraph (from Tarantulas from Uruguay*) of Theraphosa leblondi gives a good idea of the size some theraphosids reach. Theraphosidae include the largest living spiders - indeed, since the Carboniferous Megarachne was reidentified as an eurypterid, modern Theraphosidae include the largest spiders known to have existed ever.

*I rather enjoyed the Tarantulas from Uruguay page, but if you're at work you might want to be forewarned that the page does play music at you.

Theraphosidae belong to the group of spiders known as mygalomorphs. Spiders can be divided into three major groups - liphistiomorphs, mygalomorphs and araneomorphs. Liphistiomorphs are a small group found in eastern Asia that represent the sister group of all other spiders, and can be distinguished from other spiders by their retaining an obviously segmented abdomen. The other two groups of spiders can most easily be distinguished by their chelicerae (fangs). Mygalomorphs retain the more primitive condition of having the fangs directed straight up and down, and so are only able to stab down with them. Araneomorphs, by far the larger and more diverse of the three groups, have the fangs directed towards each other and are able to pinch prey or attackers between the chelicerae (the Wikipedia page for Araneomorphae has a good pair of photos showing the difference). Mygalomorphs are mostly relatively large spiders (there are a few exceptions). They also tend to be far less sexually dimorphic than many araneomorphs, with relatively little difference between males and females.

While the bites of Theraphosidae are apparently not particularly notable as far as humans are concerned, of more concern for people handling tarantulas is the presence on the abdomen of many South American species of urticating hairs - specialised hairs with minute barbs that can break off and irritate the skin of any threatening predators. Members of the subfamily Theraphosinae can even propel the hairs directly at a threat by rubbing the legs against the abdomen. Members of two genera of theraphosids have also been recorded to incorporate shed urticating hairs into the silk of egg-sacs, which was demonstrated to increase the defense offered by the egg-sac against insect egg predators (Marshall & Uetz, 1990).

The South American Avicularia metallica (image from here).

Many species of Theraphosidae are popular as pets, and females may live for up to thirty years in captivity (males, in contrast, do not survive long after mating). Unfortunately, while pet individuals of the more popular species such as the red-kneed tarantula (Brachypelma smithi) are generally captive-bred, a substantial market (in many places, such as Australia, a largely illegal market) exists in wild-caught specimens, especially of rare and unusual species. Many theraphosid species have very limited ranges, and are severely threatened by collection for the pet trade, and I have been informed that at least some Australian species have actually become extinct due to over-collection. This is especially tragic as a large proportion of the Australian theraphosid population remains undescribed, necessitating a race against time to recognise their diversity before the opportunity to protect it is lost forever.

REFERENCES

Marshall, S. D., & G. W. Uetz. 1990. Incorporation of urticating hairs into silk: a novel defense mechanism in two Neotropical tarantulas (Araneae, Theraphosidae). Journal of Arachnology 18: 143-149.

The One about Sexual Cannibalism

Sometimes, the history of people's misconceptions about organisms are nearly as interesting as the organisms themselves - not so much because of what it says about the organism itself, but what it says about us as people. One common pattern is the "pendulum swing" in conceptions about certain organisms. An originally negative over-simplification about a given organism ("wolves are savage human-killers that should be exterminated before they exterminate us"/"whales and dolphins are just fish and can be hunted as such") is replaced by a reactionary viewpoint which is more positive, but arguably just as erroneous an oversimplification ("wolves are completely harmless to humans, and would never attack somebody"/"whales and dolphins are super-intelligent, and, like, just filled with spiritual wisdom"). It is only as our attitudes mature, and the question becomes less politically charged, that opinions settle towards the generally more accurate but usually more complex middle ground.

Sexual cannibalism is one behaviour that has fallen victim to the human tendency to mythologise. Many people are aware of the idea that female spiders, mantids and other such carnivorous arthropods have a habit of eating the male during mating. Any feminist readers I have out there might be interested to consider how the popularity of this concept reflects our own attitudes on the relationship between the sexes (the female eating the male seems scandalous because, of course, we live in a society that tells us it should be the other way around). However, if you open a textbook you will probably be told that this story is generally not true. Bug Girl has recently corrected Isabella Rossellini on just this point*. For the most part, Bug Girl is right - sexual cannibalism is a fairly rare occurrence that usually only happens when things go wrong (for instance, if the male makes his move before properly placating the female). However, there is at least one species in which sexual cannibalism is an integral part of the mating process.

*Actually, speaking of societal attitudes, perhaps the most remarkable thing about the video Bug Girl has posted - other, of course, than the fact that Isabella Rossellini is making videos about arthropods in the first place - is the obvious cultural differences when it comes to talking about sex. The American interviewer with her giggling prudishness does not compare well to Rossellini's far more relaxed attitude.

That species is Latrodectus hasselti, the redback spider. The image at the top of the page (from here) shows two redbacks. The larger individual is a mature female, while the smaller white individual is a male. The genus Latrodectus has a wide distribution around the world, including the black widow (L. mactans) of North America (which does not regularly engage in sexual cannibalism), with most species having a well-deserved reputation for toxicity. The redback had done particularly well out of human civilisation - it is unclear where exactly in Australia it originated*, but it has since been spread throughout the continent, as well as establishing populations in other countries such as New Zealand and Japan. Latrodectus hasselti specialises in constructing its webs between hot, dry, facing surfaces, and humans are very good at building hot, dry, facing surfaces.

*Some people have suggested that the redback is not a native to Australia because of the absence of early records of this species, and its close association in most areas with humans. Conflicting with this is the absence of redbacks in any other part of the world, apart from areas where it has obviously been imported in Australia. It is far more likely that the redback had a much more restricted distribution in Australia prior to European settlement (probably somewhere west of the Great Dividing Range) and has since been spread to the remainder of the country.



In other Latrodectus species, the small male first climbs onto the female's web and approaches her cautiously with regular stops to vibrate the web. The female will usually chase him away a few times, but eventually she calms down and the male is able to climb onto the underside of the female as she hangs upside-down on the web, as shown above in Latrodectus hesperus (image from here). The female remains largely immobile while the male mates with her, and he is able to make his escape quite easily. In the redback, the male approaches and mounts the female as in other Latrodectus but once he has inserted his pedipalp into her he performs a back-flip that brings his abdomen alongside her mouthparts. The female, seemingly unable to resist the temptation, bites into the male and begins chewing. After a while, the male pulls away from the female and rips his badly damaged abdomen out of her grasp. Nevertheless, after a period of grooming the male returns to the female, and inserts and repositions himself as before. This time, the female does not allow him to escape - the male does not survive the second mating.

Why does the male submit himself to this fatal attack? There are a few possibilities that have been suggested. The nutrients the female receives from eating the male may aid in the development of the eggs he has fertilised. Also, the female remains mating with the male for longer while feeding on him than she would have otherwise. Not only does this allow the male more time to fertilise her eggs, it also denies other males the chance to mate with her in this time. A thesis abstract available here indicates that some males try to escape the role of victim, attempting to sneak in and mate with the female without offering themselves. However, females react even more aggressively to such cheaters, who were much more likely to be cannibalised before mating was successfully completed.

REFERENCES

Forster, R., & L. Forster. 1999. Spiders of New Zealand and their Worldwide Kin. University of Otago Press: Dunedin, in association with Otago Museum.

Taxon of the Week: Eye of the Spider

I'm afraid that today's "Taxon of the Week" must needs be a short one. I'm tutoring a lab course on invertebrate surveying this week, so I don't have the time to write an extensive post. I can only give you a whirlwind introduction to the lynx spiders of the family Oxyopidae (image above from Wikimedia).



Oxyopidae are one of the families of hunting spiders - that is, rather than building a web to catche prey in, they actively hunt for small insects. The name "lynx spider" is apparently supposed to refer to their sharp eyesight, though there seems to be some doubt as to just how sharp their eyesight is compared to, for instance, the jumping spiders of the Salticidae. Still, like other families of hunting spiders, Oxyopidae have all of their eyes directed more or less forward, and a sharp downwards bend to the front of the prosoma means that the four central eyes are looking straight ahead, as shown spectacularly well in the picture above from Ed Nieuwenhuys. In both the pictures above, if you look closely you may also make out the long spiny hairs sticking out at right angles from the legs that also seem to be characteristic of this family.



While they may not build webs for catching prey, female lynx spiders do use silk to protect their eggs, which they stand guard over until the eggs are well-developed.

What is a Daddy-Longlegs?

"Daddy-longlegs" is one of the worst animal names there is. The name is widely used and generally recognised, but causes endless confusion because it is applied to no less than three very different animals. In a brief attempt at disambiguation, these are the animals involved:

First are harvestmen of the order Opiliones (picture from UMMZ). Harvestmen are often confused with spiders, but the body is not divided into a cephalothorax and abdomen, the opisthosoma (the posterior part of the body corresponding to the abdomen) is externally segmented, the chelicerae (mouthparts) are pincers rather than fangs, and harvestmen do not produce silk. The name "daddy-longlegs" as applied to harvestmen usually refers to the group known as "long-legged harvestmen" (Palpatores). There is some uncertainty about whether Palpatores are a monophyletic group, but that's a subject for another time.

Second are spiders of the family Pholcidae (picture is from Iziko Museums of Cape Town - the object the spider is holding is the egg-sac, which is carried by the female until the eggs hatch). Pholcids are true spiders, and so have a divided body, an unsegmented abdomen, fangs, and produce silk. Here in Australia and New Zealand, the 'daddy-longlegs' that are almost ubiquitously found in houses (particularly bathrooms) are pholcids, most often the introduced Pholcus phalangioides. Offhand, there is a common belief that daddy-longlegs (either pholcids or Opiliones) are "the most poisonous spiders in existence, but their fangs are too small to pierce human skin". I have come across this story many times, and have even been assured of it by people who really should know better. This story is absolute bunkum. The University of California, Riverside site has more info.

Finally, the third group accused of being 'daddy-longlegs' are crane flies of the family Tipulidae (picture from Wikipedia). Crane flies look a bit like giant mosquitoes, but they are not blood-suckers. They are a large family - the adults are nectarivores or do not feed, while the larvae, commonly called leatherjackets, feed on vegetation. Crane flies are easily distinguished from the other 'daddy-longlegs' - the wings are a bit of a give-away.