橋本 佳明

The genus Utivarachna Kishida, 1940 currently comprises 23 species, with eight described from Borneo. We examined the type materials of the Bornean species, except for U. fukasawana Kishida, 1940, as well as newly collected specimens. As a result, we describe a new species, Utivarachna itiokai sp. nov., which belongs to the dusun-group. We also provide the first description of the female of Utivarachna ichneumon and redescribe the known Utivarachna species of Borneo.

Abstract Solenopsis invicta Buren (Hymenoptera: Formicidae; red imported fire ant) is an invasive species in several parts of the world. A major contributor to the spread of S. invicta is infested shipping containers. The vapor of allyl isothiocyanate (AITC), a naturally occurring organosulfur compound, is highly toxic to S. invicta; however, AITC is highly volatile. Microencapsulation of AITC in polyethylene (PE) resin slows the release of AITC, making it a potentially useful material for preventing S. invicta infestations. Here, we examined the efficacy of AITC microencapsulated in PE (mAITC) as a repellent against S. invicta infestation of cardboard boxes, a common containerized cargo. Using baited cardboard boxes, we found that the number of S. invicta individuals entering boxes containing an mAITC sheet was significantly less than that entering boxes without an mAITC sheet. When a PE cover, which is often used to protect carboard boxes during shipping, was used, vapor concentrations of AITC inside the boxes were increased and the number of S. invicta individuals entering the boxes was reduced almost to zero. These findings indicate that mAITC sheeting, especially in combination with a PE cover, is a promising material for the protection of containerized cardboard-box cargo against S. invicta infestation.