Just like humans with their holiday homes, time-sharing is one of
the ways in which arachnids manage to share "living space".
If we take just one type of environment - mixed woodland on an island
in the beautiful Loch Lomond in Scotland - we can see how different species
of opilionids have different patterns of seasonal abundance.
As you can see, our favourite Mitopus morio peaks in early summer and then persists into the autumn and even early winter.
There is then a temporal succession as M. morio is followed in turn by Lacinius ephippiatus, Nemastoma bimaculatum, Oligolophus hansenii, O. agrestis, O. tridens and O. (Odiellus) palpinalis. This brings us into mid-winter, after which there are relatively few harvestmen taken in pitfall traps until spring when they turn up again.
The data used for the graph shown here are derived from two years' pitfall
sampling 1971-1973, with the monthly catches for the two years being pooled.
The species' abundances are then plotted as a percentage of the species'
total.
| The actual abundances of the species are also interesting, as you can see from this listing of the overall catches for these species, as well as the rarer species caught: | |
| Nemastoma bimaculatum | 11241 |
| O. (Odiellus) palpinalis | 1339 |
| Oligolophus tridens | 1123 |
| Oligolophus agrestis | 443 |
| Lacinius ephippiatus | 298 |
| Mitopus morio | 246 |
| Oligolophus hansenii | 160 |
| Mitostoma chrysomelas | 41 |
| Oligolophus meadii | 16 |
| Rilaena triangularis | 15 |
| Opilio saxatilis | 5 |
| Megabunus diadema | 4 |
|
Total
|
14931 |
These numbers also show interesting patterns over different habitats
and are also strongly influenced by the trapping method - but more of that
later...
|
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