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June 1 - 3 , 1978 - University of Hawaii at Manoa

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VARIABILITY IN DORSAL PATTERNING AMONG POPULATIONS OF<br />

HAWAIIAN "HAPPY-FACE" SPIDERS (THERIDION SP. OR SPP.)<br />

ON THE BIG ISLAND*<br />

William P. Mull<br />

Department <strong>of</strong> Entomology<br />

Bernice Pauahi Bishop Museum<br />

Honolulu, <strong>Hawaii</strong> 96818<br />

Since the December 1972 discovery on O'ahu <strong>of</strong> an apparently<br />

undescribed comb-footed spider (Theridiidae) with a striking<br />

"happy-face" design on its back, close rel<strong>at</strong>ives have been found<br />

on Maui and the Big Island. Preliminary surveys <strong>of</strong> Big Island<br />

forests have produced over 100 specimens and revealed a remark-<br />

able spectrum <strong>of</strong> dorsal p<strong>at</strong>terning vari<strong>at</strong>ion among popul<strong>at</strong>ions <strong>of</strong><br />

these tiny (3-4 mm body length) <strong>Hawaii</strong>an leaf-dwelling spiders.<br />

Pending study by a specialist, it is unclear whether these popu-<br />

l<strong>at</strong>ions represent a single very variable species or several<br />

species. They are tent<strong>at</strong>ively assignable to the widespread genus<br />

Theridion, which includes 10 described species (plus one sub-<br />

species) endemic to Hawai'i, only one <strong>of</strong> which bears resemblance<br />

to the "happy-face" group. These previously unknown <strong>Hawaii</strong>an<br />

spiders seem to be another example <strong>of</strong> the extremes <strong>of</strong> "genetic<br />

plasticity" and "evolutionary flux" expressed among other<br />

closely-rel<strong>at</strong>ed groups <strong>of</strong> <strong>Hawaii</strong>an organisms (e.g., Anomalochrysa<br />

lacewings, Ach<strong>at</strong>inella tree snails, Metrosideros trees) in<br />

response to qenerous ecological opportunities and minimized<br />

inhibiting pressures presented to thbse groups by the unique<br />

<strong>Hawaii</strong>an environment.<br />

* Abstract

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