In the life of the fire ant, Solenopsis invicta, venom plays several important roles, including p... more In the life of the fire ant, Solenopsis invicta, venom plays several important roles, including prey capture, defense, and antimicrobial action. Although this venom's chemistry, pharmacology, and effects on humans have been extensively studied, its patterns of synthesis and use have not. We determined the ability of different-aged workers to synthesize venom, and measured the amount of venom workers delivered per sting. Newly eclosed workers contained little or no venom in their reservoirs. The rate of synthesis was highest in workers aged 1 day after adult eclosion (1.17 mg venom/day for workers with headwidths of 1 mm), declined by 75% in workers aged 15 days (0.30 mg venom/day), and was negligible thereafter. Inducing ants to sting dummies as surrogates for humans, workers were found to deliver an average of 0.66 nl per sting, amounting to 3.1% of the average individual venom supply. Older workers (foragers) delivered less venom per sting than mid-age workers (reserves) and venom dose from nest-defenders was 55% higher in the spring than in the rest of the year. Thus, fire ant venom synthesis is limited to early life, and injected venom dose appears to be modulated. Economic explanations for the observed venom-use patterns are discussed.
<p>(a) Labrum with densely spaced pore plates (GPpl). (b) Close-up of cuticle of the 8<s... more <p>(a) Labrum with densely spaced pore plates (GPpl). (b) Close-up of cuticle of the 8<sup>th</sup> abdominal tergite. Many of the pore plates and pores (GP) are less than 10 μm apart. (c) Close-up of a glandular pore plate. Its diameter is less than 2 μm.</p
<p>(a) Post-pleural gland with glandular cells (GC) and duct cells (GD) opening through the... more <p>(a) Post-pleural gland with glandular cells (GC) and duct cells (GD) opening through the pleural intersegmental membrane between the abdominal segment VIII and IX. (b, c). large glandular cells (GC) in the posterior part of the abdomen with large intra-cellular reservoirs (GR).</p
<p>(a) A lobe with trichomes and many glandular cells (GC), the ducts (GD) of which open th... more <p>(a) A lobe with trichomes and many glandular cells (GC), the ducts (GD) of which open through cuticle channels between the trichome setae. (b) Some areas of the lobes which have no trichomes, have glandular epithelia (GE) the cells of which open through cuticle channels (CuC). (c) The second cluster of gland cells on the bases of the trichome lobes the ducts of which open through the cuticle near a major tracheal tract.</p
<p>(above) Crop (Cr) and proventriculus (PrV). The crop is lined with layers of longitudina... more <p>(above) Crop (Cr) and proventriculus (PrV). The crop is lined with layers of longitudinal and transversal muscles, and in the lumen the sclerotized spines are visible. (below) The transition from crop via proventriculus to midgut (MG). The midgut is endowed with many diverticula (DiV) along its entire length.</p
<p>The interconnected nest chambers are set in gypsum plaster and covered by a glass plate.... more <p>The interconnected nest chambers are set in gypsum plaster and covered by a glass plate. The internal nest opens into an arena where food for the ants is provided and where beetles are placed for adoption experiments.</p
<p>Above: <i>Lomechusoides strumosus</i>; Below: <i>Lomechusa pubicollis&... more <p>Above: <i>Lomechusoides strumosus</i>; Below: <i>Lomechusa pubicollis</i>. AG indicates the lobes of the paratergites with the dense endowment with trichome hairs. This area is richly endowed with exocrine gland which are called “adoption glands”.</p
<p>(above) Scanning electron microscopic image of the ventral side of the femur. Box indica... more <p>(above) Scanning electron microscopic image of the ventral side of the femur. Box indicates the location of the histological preparation shown in bottom panel. (below) Glandular cells (GC) inside the femur.</p
<p>(a) Overview of part of the head. Br: brain; M: muscle; GC: glandular cells near the bas... more <p>(a) Overview of part of the head. Br: brain; M: muscle; GC: glandular cells near the base of the mandibles. (b) Close-up of these gland cells that open through the cuticle channels (CuC). (c) Longitudinal section through the mouth parts. Lbr: labrum; M: mandible, with an epithelium consisting of sensory and glandular cells (GC/SC) in the posterior. Ga: galea. (d) Glandular cells (GC) in the labium (Lab).</p
<p>(above) Often the beetle exudes an opaque, white droplet from its abdominal top, which i... more <p>(above) Often the beetle exudes an opaque, white droplet from its abdominal top, which is taken up by the ant. Presumably it originates from the hindgut/rectum. (below) Occasionally a whitish, clear secretion appears at the lateral sides of the abdomen where the post-pleural gland opens. This secretion is also licked by the ants.</p
<p>(a) Longitudinal section through the hindgut (HG) and rectum (R). (b) and (c) Transversa... more <p>(a) Longitudinal section through the hindgut (HG) and rectum (R). (b) and (c) Transversal sections showing the large gland cell nuclei (GCNu) in the hindgut epithelial cells (HGE). (M) Muscle tissue surrounding hindgut layer. (d) Transversal section of hindgut showing the microvilli structure (MiVi) of the hindgut cells.</p
<p>Beetles fed with labeled honey water were placed with familiar or unfamiliar beetles. Be... more <p>Beetles fed with labeled honey water were placed with familiar or unfamiliar beetles. Beetles from both groups successfully obtained food from their host ants, but familiar beetles obtained significantly more food than unfamiliar beetles (bars are means with standard errors).</p
<p>Glandular epithelium (GE) in antennal segments of <i>Lomechusoides strumosus</i... more <p>Glandular epithelium (GE) in antennal segments of <i>Lomechusoides strumosus</i>.</p
<p><i>Lomechusoides strumosus</i> (a) and <i>Lomechusa pubicollis</i&g... more <p><i>Lomechusoides strumosus</i> (a) and <i>Lomechusa pubicollis</i> (b) both have a large protheca (PT) in contrast to <i>Pella sp</i>. (c) where the protheca is much smaller.</p
<p>The green area of abdominal segments II to V is the adoption gland complex (AG). Between... more <p>The green area of abdominal segments II to V is the adoption gland complex (AG). Between abdominal segments VI and VII is the defense tergal gland or repellent gland, the reservoir (Re) of which opens between these two segments. The repellent secretion is a mixture of the secretions of the glandular epithelium (RGE) and the glandular cells (RGC). PlG indicates the location of the post-pleural gland. HG: hindgut; R: rectum. The blue area indicates the appeasement gland complex.</p
<p>(a) and (c) Longitudinal sections through the femur showing the densely packed glandular... more <p>(a) and (c) Longitudinal sections through the femur showing the densely packed glandular cells (GC) with the cuticle channels (CuC). (b) and (d) Longitudinal sections through tibia proximate to the femur, showing the dense layer of gland cells with ducts through the cuticle.</p
<p>The host ant <i>Formica sanguinea</i> regurgitates food to the beetle (above... more <p>The host ant <i>Formica sanguinea</i> regurgitates food to the beetle (above). The ant’s mandibles are opened, the labium is extended. This resembles the feeding behavior among adult ants. (below) Occasionally two beetles have mouth to mouth contact, however we could not find evidence that they exchange food.</p
<p>Often the ant approaches the beetle and licks its head (a). The beetle seeks contact wit... more <p>Often the ant approaches the beetle and licks its head (a). The beetle seeks contact with the ant’s labium (b, c). This usually leads to regurgitation of food by the ant. During the trophallactic act shown in (d), the ant’s mandibles are closed, but the labium is extended. This somewhat resembles the feeding behavior which ants exhibit during larval feeding.</p
<p>(a,b,c,d,) Different views and magnifications of the typical hair tufts (AT) the beetle ... more <p>(a,b,c,d,) Different views and magnifications of the typical hair tufts (AT) the beetle males display on their third and fourth antennal segments.</p
In the life of the fire ant, Solenopsis invicta, venom plays several important roles, including p... more In the life of the fire ant, Solenopsis invicta, venom plays several important roles, including prey capture, defense, and antimicrobial action. Although this venom's chemistry, pharmacology, and effects on humans have been extensively studied, its patterns of synthesis and use have not. We determined the ability of different-aged workers to synthesize venom, and measured the amount of venom workers delivered per sting. Newly eclosed workers contained little or no venom in their reservoirs. The rate of synthesis was highest in workers aged 1 day after adult eclosion (1.17 mg venom/day for workers with headwidths of 1 mm), declined by 75% in workers aged 15 days (0.30 mg venom/day), and was negligible thereafter. Inducing ants to sting dummies as surrogates for humans, workers were found to deliver an average of 0.66 nl per sting, amounting to 3.1% of the average individual venom supply. Older workers (foragers) delivered less venom per sting than mid-age workers (reserves) and venom dose from nest-defenders was 55% higher in the spring than in the rest of the year. Thus, fire ant venom synthesis is limited to early life, and injected venom dose appears to be modulated. Economic explanations for the observed venom-use patterns are discussed.
<p>(a) Labrum with densely spaced pore plates (GPpl). (b) Close-up of cuticle of the 8<s... more <p>(a) Labrum with densely spaced pore plates (GPpl). (b) Close-up of cuticle of the 8<sup>th</sup> abdominal tergite. Many of the pore plates and pores (GP) are less than 10 μm apart. (c) Close-up of a glandular pore plate. Its diameter is less than 2 μm.</p
<p>(a) Post-pleural gland with glandular cells (GC) and duct cells (GD) opening through the... more <p>(a) Post-pleural gland with glandular cells (GC) and duct cells (GD) opening through the pleural intersegmental membrane between the abdominal segment VIII and IX. (b, c). large glandular cells (GC) in the posterior part of the abdomen with large intra-cellular reservoirs (GR).</p
<p>(a) A lobe with trichomes and many glandular cells (GC), the ducts (GD) of which open th... more <p>(a) A lobe with trichomes and many glandular cells (GC), the ducts (GD) of which open through cuticle channels between the trichome setae. (b) Some areas of the lobes which have no trichomes, have glandular epithelia (GE) the cells of which open through cuticle channels (CuC). (c) The second cluster of gland cells on the bases of the trichome lobes the ducts of which open through the cuticle near a major tracheal tract.</p
<p>(above) Crop (Cr) and proventriculus (PrV). The crop is lined with layers of longitudina... more <p>(above) Crop (Cr) and proventriculus (PrV). The crop is lined with layers of longitudinal and transversal muscles, and in the lumen the sclerotized spines are visible. (below) The transition from crop via proventriculus to midgut (MG). The midgut is endowed with many diverticula (DiV) along its entire length.</p
<p>The interconnected nest chambers are set in gypsum plaster and covered by a glass plate.... more <p>The interconnected nest chambers are set in gypsum plaster and covered by a glass plate. The internal nest opens into an arena where food for the ants is provided and where beetles are placed for adoption experiments.</p
<p>Above: <i>Lomechusoides strumosus</i>; Below: <i>Lomechusa pubicollis&... more <p>Above: <i>Lomechusoides strumosus</i>; Below: <i>Lomechusa pubicollis</i>. AG indicates the lobes of the paratergites with the dense endowment with trichome hairs. This area is richly endowed with exocrine gland which are called “adoption glands”.</p
<p>(above) Scanning electron microscopic image of the ventral side of the femur. Box indica... more <p>(above) Scanning electron microscopic image of the ventral side of the femur. Box indicates the location of the histological preparation shown in bottom panel. (below) Glandular cells (GC) inside the femur.</p
<p>(a) Overview of part of the head. Br: brain; M: muscle; GC: glandular cells near the bas... more <p>(a) Overview of part of the head. Br: brain; M: muscle; GC: glandular cells near the base of the mandibles. (b) Close-up of these gland cells that open through the cuticle channels (CuC). (c) Longitudinal section through the mouth parts. Lbr: labrum; M: mandible, with an epithelium consisting of sensory and glandular cells (GC/SC) in the posterior. Ga: galea. (d) Glandular cells (GC) in the labium (Lab).</p
<p>(above) Often the beetle exudes an opaque, white droplet from its abdominal top, which i... more <p>(above) Often the beetle exudes an opaque, white droplet from its abdominal top, which is taken up by the ant. Presumably it originates from the hindgut/rectum. (below) Occasionally a whitish, clear secretion appears at the lateral sides of the abdomen where the post-pleural gland opens. This secretion is also licked by the ants.</p
<p>(a) Longitudinal section through the hindgut (HG) and rectum (R). (b) and (c) Transversa... more <p>(a) Longitudinal section through the hindgut (HG) and rectum (R). (b) and (c) Transversal sections showing the large gland cell nuclei (GCNu) in the hindgut epithelial cells (HGE). (M) Muscle tissue surrounding hindgut layer. (d) Transversal section of hindgut showing the microvilli structure (MiVi) of the hindgut cells.</p
<p>Beetles fed with labeled honey water were placed with familiar or unfamiliar beetles. Be... more <p>Beetles fed with labeled honey water were placed with familiar or unfamiliar beetles. Beetles from both groups successfully obtained food from their host ants, but familiar beetles obtained significantly more food than unfamiliar beetles (bars are means with standard errors).</p
<p>Glandular epithelium (GE) in antennal segments of <i>Lomechusoides strumosus</i... more <p>Glandular epithelium (GE) in antennal segments of <i>Lomechusoides strumosus</i>.</p
<p><i>Lomechusoides strumosus</i> (a) and <i>Lomechusa pubicollis</i&g... more <p><i>Lomechusoides strumosus</i> (a) and <i>Lomechusa pubicollis</i> (b) both have a large protheca (PT) in contrast to <i>Pella sp</i>. (c) where the protheca is much smaller.</p
<p>The green area of abdominal segments II to V is the adoption gland complex (AG). Between... more <p>The green area of abdominal segments II to V is the adoption gland complex (AG). Between abdominal segments VI and VII is the defense tergal gland or repellent gland, the reservoir (Re) of which opens between these two segments. The repellent secretion is a mixture of the secretions of the glandular epithelium (RGE) and the glandular cells (RGC). PlG indicates the location of the post-pleural gland. HG: hindgut; R: rectum. The blue area indicates the appeasement gland complex.</p
<p>(a) and (c) Longitudinal sections through the femur showing the densely packed glandular... more <p>(a) and (c) Longitudinal sections through the femur showing the densely packed glandular cells (GC) with the cuticle channels (CuC). (b) and (d) Longitudinal sections through tibia proximate to the femur, showing the dense layer of gland cells with ducts through the cuticle.</p
<p>The host ant <i>Formica sanguinea</i> regurgitates food to the beetle (above... more <p>The host ant <i>Formica sanguinea</i> regurgitates food to the beetle (above). The ant’s mandibles are opened, the labium is extended. This resembles the feeding behavior among adult ants. (below) Occasionally two beetles have mouth to mouth contact, however we could not find evidence that they exchange food.</p
<p>Often the ant approaches the beetle and licks its head (a). The beetle seeks contact wit... more <p>Often the ant approaches the beetle and licks its head (a). The beetle seeks contact with the ant’s labium (b, c). This usually leads to regurgitation of food by the ant. During the trophallactic act shown in (d), the ant’s mandibles are closed, but the labium is extended. This somewhat resembles the feeding behavior which ants exhibit during larval feeding.</p
<p>(a,b,c,d,) Different views and magnifications of the typical hair tufts (AT) the beetle ... more <p>(a,b,c,d,) Different views and magnifications of the typical hair tufts (AT) the beetle males display on their third and fourth antennal segments.</p
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