Posted by Mark Conboy
Eastern Ontario has its fair share of interesting and charismatic spiders. There are the argiopes (Argiope spp.), whose webs are decorated with an ultraviolet-reflective stabilimentum, presumably to attract insect prey; there are the enormous and parentally-minded pisaurids (Dolomedes and Pisaurina spp.) which carry their eggs with them in a bundle of silk to keep them safe from predators and parasitoids; there are also the beautifully marked jumping spiders (Salticidae) whose leaps propel them many times their own body length, and for safety sake always tether themselves with a string of silk. But among the most exciting spiders in our region is the highly venous and exceeding beautiful northern widow (Latrodectus variolus). I’ve found not one, but two northern widows at Queen’s University Biological Station this year; perhaps the first year this species has ever been documented there.
The northern widow is a close relative of the better known and often maligned black widow (L. mactans). Black widows are typically confined to the southern United States and their distribution does not normally include Canada. Occasionally black widows (and other charismatic subtropical invertebrates) arrive in Canada on shipments of produce from the southern states but probably do not survive long outside of buildings. Northern widows however are native, though they seem to be fairly rare throughout most of Eastern Ontario. In southwestern Ontario they are a little more common, with several large localized populations. Throughout much of their range though they are patchily distributed and not often encountered. Many people are not even aware of their existence in the province.
The first of the two females at QUBS was found below a black light at Ironwood Cottage on QUBS Point. She had constructed a nest and egg sac under a cinder block. She preyed on a mixture of insects attracted to the black light including June beetles (Phyllophaga spp.) and medium-sized moths. The second female was underneath a flat rock on a rock barren at the Elbow Lake Environmental Education Centre. The only prey item found in this female’s web were parts of a Pennsylvania woodroach (Parcoblatta pennsylvanica). This female also had an egg sac.
According to most sources northern widows can produce painful and potentially dangerous bites, but apparently no fatalities have been reported from the bite of this species, at least in Ontario. Widows in general are retiring spiders that typically only bite humans during accidental interactions. Their neurotoxic venom can cause pain and breathing difficulties and in the case of the black widow, can be fatal to young children or the infirmed. Northern widow bites should be taken seriously and a physician should be seen if you are unlucky enough to be bitten by one.
Next summer year I’ll be on the lookout for more northern widows across the rock barrens and inside the various abandoned buildings at QUBS. It’s impossible to say if we’ve always had a small and cryptic population of this species that’s just gone unnoticed, or if northern widows have only recently arrived here. The presence of eggs sacs clearly shows that whatever the history of widows at QUBS was, there is currently a reproductive population.