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Abstract

Workers of the polymorphic fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) show modest changes of shape with increases in body size. These shape changes (allometries) have been described only for workers taken from mature colonies of the monogyne social form. For the study reported here, workers were collected from small and large monogyne and large polygyne colonies for tests of the effects of colony size and social form on allometry. The differential growth of body parts in relation to total body growth was determined by measurement of all major body parts and regression of the logs of these measurements, or their ratios, on the log of the body size. The slopes of these regressions defined the allometric relationships, and the slopes for these three types of colonies were compared for determination of the influence of colony size and social form on allometric rules. Most allometric constants did not differ with colony size or social form, but head shape, relative antennal size, and alinotum shape did. For a given worker size, heads of workers from small monogyne colonies or from polygyne colonies were narrower above the eyes. Antennae of workers from large monogyne colonies were relatively shorter than those from small monogyne or polygyne colonies (which did not differ). Alinotum heights of small workers from small monogyne colonies were greater than those from large monogyne or polygyne colonies (which were isometric and did not differ). These observed differences in allometric constants suggest that the relative growth rules are not completely determined by worker body size but are affected by colony size and social form. These differences are discussed in light of the growth of imaginal discs under conditions of fixed resources.

Keywords: imaginal discs, isometry, growth rate, nutrition, polymorphism, size and shape
Abbreviations: AL, alinotum length; AH, alinotum height; HL, head length; HW1, head width across the eyes; HW2, head width above the eyes, ca. 75% of the distance from the clypeus to the apex of the head; HW3, head width below the eyes, ca. 25% of the distance from the clypeus to the head apex; FL, flagellum length; SC, scape length; AN, antennal length (FL + SC); GL, length of first gaster segment; GW, width of first gaster segment; FE(1,2,3), femur length; OLS, ordinary least squares regression; RMA, reduced major axis regression; TB(1,2,3), tibia length; TA(1,2,3), tarsus length; LG(1,2,3), total leg length (FE +TB + TA); PL(1,2), petiole length; PH(1,2), petiole height; WT, weight (mg); BL, total body length (HL + AL +PL1 + PL2 + GL)

Correspondence: ^amba04@fsu.edu, ^b*tschinkel@bio.fsu.edu, *Corresponding author

Received: 12 November 2008 | Accepted: 11 May 2009 | Published: 6 July 2010

Copyright: This is an open access paper. We use the Creative Commons Attribution 3.0 license that permits unrestricted use, provided that the paper is properly attributed.  

ISSN: 1536-2442 | Volume 10, Number 94

Araujo MB, Tschinkel WR. 2010. Worker allometry in relation to colony size and social form in the fire ant Solenopsis invicta. Journal of Insect Science 10:94, available online: insectscience.org/10.94