Workers of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), range in size from ≈0.5 to 1.5 mm in headwidth. Such size variation is thought to enable a more efficient division of labor, because some worker sizes may be better suited to performing particular tasks. Here, I focus on the task of nest defense, where efficiency and effectiveness may depend on having appropriately sized workers respond to particular types of threats. Specifically, I tested whether the size of responding workers differs between two magnitudes of nest disturbance (light, insect-like versus heavy, vertebrate-like), and I investigated how both sting length and the amount of venom workers contain, key defensive traits, vary with worker size. Workers responding to heavy, vertebrate-like nest disturbances were larger than those responding to light, insect-like disturbances. Between the light and heavy disturbances, the proportion of minor (small) workers responding dropped, whereas that of major (large) workers increased five-fold. Although the relationship between sting length and worker size is not directly proportional, the average sting length of majors is ≈0.20 mm (or 40%) greater than that of minors, with little overlap in range. The relationship between worker size and the amount of venom they contain is also positive. So, vertebrate-magnitude nest disturbances are met with greater proportions of large S. invicta workers than are insect-magnitude disturbances, and these larger workers bring with them longer stings and larger venom arsenals, which may increase their effectiveness against such relatively large, thicker-skinned threats.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 103 • No. 4