A Preliminary Look At The Phenology of Adult Ozyptila praticola (Thomisidae) in Western Washington

Whenever I take a break from collecting, I'm itching the whole time to resume field work as soon as I can.  But breaks do give me time to take an unhurried look at the data I've recently collected to see whether I've learned anything unexpected.  I've been doing this with my Ozyptila praticola project data.

The goal of the O. praticola project has been simply to determine the distribution of this introduced crab spider in Washington state, as found in the fallen conifer cone microhabitat.  But in the process of pursuing that goal, I've collected some interesting life history data on the species.  In this case, adult phenology.

The Spiders of Europe and British Arachnological Society's Spider Recording Scheme ("SRS") web pages for O. praticola both report that mature males and females have been collected every month of the year in their regions of coverage. Similarly, within their local range here in Washington, I have found adult O. praticola present every month that I've searched (February through November) except for February, a woefully under-sampled month represented so far by only one 50-cone sample.

Before graphing the monthly occurrence of females and males in my collection, I standardized numbers of specimens of each sex I collected each month by converting them to a per 100 cones tapped basis.  I did this because sampling effort -- defined here as numbers of cones tapped per month -- varied greatly from month to month (see chart, right).

The resulting chart shows that female O. praticola have been present in my samples in fairly consistent concentrations of about 1 to 2 spiders per 100 cones every month I've sampled (excluding February, as previously discussed).  In contrast, I found males in tapped cones only in spring (April & May) and fall (September & October), and at varying concentrations.

Adapted from British Arachnological Society's
Spider Recording Scheme

Although SRS reported O. praticola males present every month, it also showed a bimodal distribution with more males having been collected in May & June and, to a lesser degree, in September, than any other month (see chart, right).  Unfortunately, it is not possible to know whether this apparent similarity in patterns between my data and data reported by SRS is meaningful since it seems doubtful that the SRS data were standardized for sampling effort, as mine were.  The SRS results could be explained simply by more British spider collectors being active in spring and fall than other seasons.

Note that my phenology chart is based on preliminary data from a study not yet completed.  So far, I've tapped 268 O. praticola from 1,895 conifer cones.  Of those 268 O. praticola, 29 (11%) were female, 14 (5%) were male and 225 (84%) were juvenile.  That's not a lot of specimens to base any conclusions on.  Still, it's more data than we had a year ago, which was almost nil.  I am excited to know whether the patterns in my chart will change with the addition of more data.  And so, as usual, I am itching more than ever to get back out into the field.