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  • 1
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The morphology of sternal glands and associated cuticular specializations are described for female polistine social wasps. Their distribution among 25 of the 28 genera of the subfamily is examined in light of what is known of the functions of these glands. Species in which queens found colonies independently of workers (four genera plus part of Ropalidia) have clusters of ducted gland cells on the sixth (terminal) gastral sternite. In all species examined the gland cells open into a tuft of long setae which probably functions as a reservoir/applicator brush. There is at least circumstantial evidence for all five genera that this gland produces an ant repellent substance that is smeared onto the nest petiole, where it serves as a defensive barrier against ants. The remaining genera (20 plus part of Ropalidia) consist of species in which queens are accompanied by a swarm of workers in the initiation of a new colony. In 12 of these genera females have a gland of ducted cells on sternite 5 (penultimate), associated with cuticular sculpturing of various types. Experimental or circumstantial evidence for several of these genera indicates that the product of this gland is used to lay an odor trail that guides the swarm from the parent nest to a new nest site. One genus has a similar gland on the sixth sternite, another has glands on both the fifth and the sixth, and the remaining six genera lack any evidence of sternal glands. The independent-founding species of Ropalidia have a sixth sternal gland associated with a tuft of setae, while the swarm-founding species have the tuft but lack the gland. Our interpretation of this is that the gland produces an ant repellent substance in the independent-founding species, but in the swarm-founding Ropalidia such a substance is of little value and so the gland has been lost.
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  • 2
    ISSN: 1420-9071
    Keywords: Divison of labor ; Polybia occidentalis ; Hymenoptera ; Vespidae ; age polyethism ; lipid content ; colony efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Recent models of energetically efficient division of labor in eusocial insects predict that risky tasks will be performed by workers with low nutrient content. We measured changes in workers' nutrient stores (chloroform: methanol extractable lipids) in relation to age-based division of labor in the eusocial waspPolybia occidentalis to test this prediction. Distributions of age of first performance differed among task sets; tasks at increasing distance from the nest interior were performed later in life. However, individuals varied in the rate of passage through the task sequence. Weight of extractable lipids, corrected for differences in body weight, decreased with time elapsed since first performance of tasks outside the nest. Lipid content had a weaker negative relationship with adult age. Therefore, patterns of lipid decrease reflected individual differences in age polyethism. Age-based division of labor, with performance of risky tasks delayed until late in life by workers with depleted nutrient stores, may have evolved as an energy saving mechanism for insect colonies.
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  • 3
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Qualitative Unterschiede im Nestbau von 12Polistes-Arten werden beschrieben. Die Waben vonFuscopolistes spp.,P. Palisotius major undP. Epicnemius pacificus waren horizontal angelegt, sie hatten entweder eine ovale oder runde Form mit einem zentralen Pedicellus; dagegen waren die Waben vonP. Aphanilopterus spp. tropfenförmig mit einem azentralen oder seitlichen Pedicellus. Der Winkel zwischen Pedicellus und Substrat betrug bei allen Arten ungefähr 90°. Die vierFuscopolistes-Arten bauten die erste Zelle in der Regel vertikal ungeachtet der jeweiligen Neigung des Substrats, wodurch der Winkel zwischen Nest und Substrat verkleinert wurde. Im Gegensatz dazu wurde bei den sechs untersuchtenAphanilopterus-Arten der Winkel zwischen Nest und Substrat durch die Anlage der ersten Zelle vergrößert. Der mittlere Zellendurchmesser war mit der Kopfbreite signifikant korreliert. Alle Arten hörten mit der Verlängerung der Zellen auf, sobald die darin befindlichen Larven sich verpuppt hatten.P. Aphanilopterus canadensis (Brasilien) besaß den größten mittleren Divergenzwinkel der Zellen, sie war auch die einzige der untersuchten Arten, die ihre Nester regelmäßig in Form kleiner, eng benachbarter Waben baute. Bei vielen Arten änderte sich der Winkel zwischen der Wabe und dem Pedicellus im Verlauf des Nestbaus. Arten der gemäßigten Klimazonen tendierten dazu, den Pedicellus zu verstärken, sie bauten sekundäre Pedicellen und fügten auch Baumaterial dem Substrat an. Ob Baumaterial auf den Puppendeckel und auf die Rückseite der Wabe angebracht wurde, war bei den Arten ebenso variabel wie die Festigkeit und die Farbe der Nester und die Form der Rückseite der Zellen.
    Notes: Summary Measurements were taken from the nests of 12 species ofPolistes wasps and qualitative differences described. The combs of theFuscopolistes spp.,P. Palisotius major andP. Epicnemius pacificus were horizontal and either oval or round with a central petiole, while those of theP. Aphanilopterus spp. were tear-shaped with eccentric or lateral petioles. For all species the angle of the petiole to the substrate was close to 90°. The fourFuscopolistes species usually built the first cell vertically, regardless of the substrate angle, and thus reduced the angle of the nest. In contrast, the angle of the first cell increased the nest angle of the 6Aphanilopterus species studied. A regression of average cell diameter on headwith was significant. All species stopped lengthening cells after larvae pupated in them.P. (A.) canadensis (Brazil) exhibited the greatest average angle of cell divergence and was also the only wasp investigated that regularly built its nest a several small combs in close proximity. In many species the comb angle with respect to the petiole changed during construction. Temperate species tended do add more pulp to the petiole of the nest than did tropical species, built secondary petioles, and added pulp to the substrate. Whether or not pulp is added to pupal caps and comb back, paper strength and color, and the shape of cell backs were also variable among species.
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  • 4
    ISSN: 1420-9098
    Keywords: Foraging ; reliability ; task performance ; wasps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Foragers of the neotropical swarm-founding waspPolybia occidentalis showed improved task performance, as indicated by foraging success rate, with foraging age. Foragers also spent significantly more time in the field on foraging trips as they aged, while foraging rate did not change with age. These patterns were not explained by directional changes in resource availability or colony need over time. We compare these results to earlier findings on changes in task performance with experience in social insect foragers, and suggest that increases in forager persistence in the field explain improved foraging success with experience.
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  • 5
    ISSN: 1420-9098
    Keywords: Alarm ; venom ; interspecific communication ; nesting association ; Vespidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We studied interspecific alarm communication between two species of social wasps in a nesting association in northwestern Costa Rica by testing the alarm responses ofPolybia occidentalis andMischocyttarus immarginatus to venom of both species. This is the first investigation of alarm pheromone in the genusMischocyttarus. M. immarginatus did not respond with alarm behavior to the venom of either species.P. occidentalis, which responds to its own venom with alarm behavior (Jeanne, 1981), also responded with alarm behavior to the venom ofM. immarginatus, but with much less intensity. Since heterospecific venoms did not release species-typical levels of alarm behavior, we conclude that interspecific alarm signalling plays no role in the nesting association.
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  • 6
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung O.W. Richards hat in letzter Zeit eine exocrine Drüse entdeckt, deren Offnung sich am fünften (Penultimal) Sterniten von Weibchen befindet. Diese Insekten gehören zu einer ganzen Zahl von Polybiine Wespen Arten. Wir beschreiben hier die Morphologie einer Drüse, bestimmt durch Licht-Microscopie, in vier Arten vonPolybia. Die Drüsenzellen haben individuelle Offnungen an der Oberfläche des Sterniten, wo ihre Absonderung in einem von der intersegmentalen Membrane Behälter aufgehoben wird. Die Anderungen in der sternalen Cuticula, wo sich die Drüsenöffnung befindet, wurden in 12Polybia Arten mit dem Elektronen-mikroskop untersucht. Wir fanden 2 Typen von Anderungen: bei 5 Arten öffnet sich die Drüse in eine transverse Rinne, und bei 7 Arten bildet die Cuticula aufrechte Schuppen. Es hat den Anschein daß Drüsen dort grösser sind wo Rinnen vorkommen, obwohl das Insekt an sich nicht grösser ist.
    Notes: Summary O.W. Richards recently discovered an exocrine gland that opens on the fifth (penultimate) sternite of females of many species of polybiine wasps. Recent experimental evidence indicates that this gland produces the trail pheromone used to guide the swarm during emigration to a new nest site. In the present paper we describe the morphology of the gland in four species ofPolybia as seen using light microscopy. The gland cells open via individual ducts onto the surface near the anterior margin of the sternite, where their secretion is evidently stored in a reservoir formed by the intersegmental membrane. The modifications of the sternal cuticle associated with the gland opening, which we examined in 12Polybia species using scanning electron microscopy, are of two types: in five species the gland opens into a transverse groove, while in the other seven the cuticle is raised into erect scales. There is some evidence that the groove type is correlated with larger gland size; there is only a poor correlation with larger body size.
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  • 7
    ISSN: 1420-9098
    Keywords: Behavioral control ; behavioral development ; contingency ; life span
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We studied the effects of intrinsic colony characteristics and an imposed contingency on the life span and behavior of foragers in the swarm-founding social waspPolybia occidentalis. Data were collected on marked, known-age workers introduced into four observation colonies. To test the hypothesis that colony demographic features affect worker life span, we examined the relationships of colony age and size with worker life span using survivorship analysis. Colony age and size had positive relationships with life span; marked workers from two larger, older colonies had longer life spans (¯X = 24.7 days) than those from two smaller, younger colonies (¯X = 20.1 days). We quantified the effects of experimentally imposed nest damage on forager behavior, to determine which of three predicted behavioral responses by foragers to this contingency (increased probability of foraging for building material, increased rate of foraging, or decrease in age of onset of foraging) would be employed. Increasing the colony level of need for materials used in nest construction (wood pulp and water) by damaging the nests of two colonies did not cause an increase in either the proportion of marked workers that gathered nest materials or in foraging rates of marked individuals, when compared with introduced workers in two simultaneously observed control colonies. Instead, nest damage caused a decrease in the age at which marked workers first foraged for pulp and water. The response to an increase in the need for building materials was an acceleration of behavioral development in some workers.
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  • 8
    ISSN: 1420-9098
    Keywords: Apoica ; social wasps ; Hymenoptera ; Vespidae ; Polistinae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Colonies and nests ofApoica pallens in the llanos region of Venezuela range from small foundress nests to large mature colonies. Nests are sited on small diameter, near-horizontal branches in a variety of shrub and tree species. During the day, adult wasps cluster on the face of the nest in an array that seems to be determined by orientation to gravity; defense of the colony against parasitoids and ants by the resting wasps may be more a passive than an active behavior. Wasps fan their wings to cool the colony during the day, but no foraging for water accompanies the fanning behavior. Nightly foraging activity begins with the explosive departure from the nest of hundreds of wasps, most of which rapidly return. Moderate foraging levels early at night give way to very low foraging levels in pre-dawn hours. The period of moderate foraging may be extended for longer hours during increased moonlight. Foraging wasps collect arthropod provisions for larvae. Larvae produce a trophallactic saliva; adults engage in inter-adult trophallaxis; brood are cannibalized. During cluster formation prior to swarm emigration, adult wasps do not appear to scent-mark substrates such as leaves. Instead,A. pallens exhibits a calling behavior, unique among polistine wasps studied to date, in which the gaster is held rigidly away from the thorax and metasomal sternal glands are exposed. Swarms can emigrate during the day.A. pallens may incorporate absconding and colony relocation as features of its colony cycle in the highly seasonal llanos.
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  • 9
    ISSN: 1420-9098
    Keywords: Hymenoptera ; social wasps ; Polybia ; prey capture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Polybia sericea (Hymenoptera: Vespidae) prey foraging was studied by following individual foragers as they hunted in the field, by observing how wasps handled prey once they had captured it, and by observing wasps as they returned to the nest with prey. Wasps were most likely to forage for prey between 0700 and 1300 hours and between 1600 and 1700 hours. The prey foraging sequence consisted of the behaviours high flight, search, touch, land, groom, walk, bite and malaxate. Captured small prey were malaxated and carried to the nest. Wasps removed the gut from large prey and dragged the meat up a twig or grass stem. A load of the meat was then bitten off and malaxated; the remainder was cached while the wasp made an orientation flight and returned to the nest. The forager returned within minutes for the remainder of the prey. Experiments demonstrated that caching the prey remains above the ground rather than close to the ground, where the prey are generally captured, reduces the chance that the prey will be found and expropriated by ants.
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  • 10
    ISSN: 1420-9098
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Weibchen jeden Alters, Kasten als wohl als solche mit früherer Kopulationserfahrung verursachten geschlechtliches Verhalten bei Männchen der sozialen WespePolistes fuscatus (F.). Gifte der Arbeiter, Königinnen, unbefruchteten Weibchen 〉 24 Stunden alt und befruchtete Weibchen 〉 14 Tage alt waren wirksam und riefen männliches sexual Verhalten hervor. Aus diesem Grunde enthalten diese Gifte Geschlechtspheromone. Gift von Weibchen 〈 15 h alt riefen kein heufigeres Geschlechtsverhalten hervor als Kontrol-Weibchen.
    Notes: Summary Females of all ages, castes, and prior mating experiences elicited sexual behavior in males of the social waspPolistes fuscatus (F.). The venoms of workers, queens, uninseminated gynes more than 24 hours old, and inseminated gynes more than 14 days old were effective in stimulating male sexual behavior, and thus contained sex pheromone. The venom of gynes less than 15 hours old did not stimulate a significantly greater frequency of male sexual behavior than did the control.
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