Soldier production and maintenance of soldier proportions in laboratory experimental groups ofCoptotermes formosanus Shiraki
SummaryExperimental groups of 100 percent pseudergates ofCoptotermes formosanus Shiraki were set up in the laboratory and allowed to differentiate for either 4, 8 or 12 weeks. The average percentage of pseudergates differentiating into presoldiers and soldiers at these time intervals was 3.8, 14.2, and 21.9 percent, respectively. Differentiation to the soldier caste was affected both by initial group size and colony origin. Groups initially composed of 100 pseudergates produced a significantly smaller proportion of soldiers than did groups of 300, 500, or 1000. Recently collected field colonies produced soldiers at significantly higher rates than one which had been maintained in the laboratory for 8 years. The number of soldiers produced was highly correlated with the total number of all individuals at 4, 8, and 12 weeks, which indicates a precise physiological mechanism for regulating soldier proportions.Experimental groups were also set up with “normal” (24 percent), “below normal”, and “above normal” initial proportions of soldiers with pseudergates. ‘When soldiers were present in “below normal” proportions they inhibited the presoldier production, approached the norm. This species can tolerate and will maintain an exceptionally high proportion of soldiers (ca. 38 percent) which is far above the assumed “normal” proportion. Many, but not all, of the excess soldiers were probably eliminated by cannibalism. Groups severely overloaded with soldiers succumbed to microbial contamination after the excess soldiers starved to death.From these results I conclude that colonies ofC. formosanus do maintain numerically constant proportions of soldiers within broad limits. Thus, colonies might be controlled by chemically inducing the production of superfluous soldiers. Successful control would require the proportion of soldiers be so great that the pseudergates could not effectively reduce the numbers of soldiers by cannibalizing the excess individuals before their death by starvation resulted in microbial contamination of the entire colony.ResumeDes groupes expérimentaux, entièrement constitués de pseudergates deCoptotermes formosanus Shiraki, se sont différenciés librement au laboratoire pendant 4, 8 ou 12 semaines. Les pourcentages moyens de pseudergates qui se sont différenciés en soldats ou en soldats blancs ont été de 3,8 pour cent au bout de 4 semaines, 14,2 pour cent au bout de 8 semaines et 21,9 pour cent au bout de 12 semaines. La différenciation en soldat a été influencée par la taille initiale du groupe et le lieu d'origine de la colonie. Des groupes composés initialement de 100 pseudergates ont produit significativement une proportion plus faible de soldats que des groupes de 300, 500 ou 1000. Des colonies qui venaient d'être récoltées dans la nature ont fourni des taux significativement plus élevés de soldats qu'une colonie qui était gardée au laboratoire depuis 8 ans. Le nombre de soldats obtenu était en corrélation hautement positive avec le nombre total d'individus au bout de 4, 8 et 12 semaines. Ceci indique qu'il existe un mécanisme physiologique précis dans la régulation des proportions de soldats dans les colonies.Nous avons aussi constitué des groupes expérimentaux qui comprenaient des proportions «normales» (24%), «en dessous de la normale» et «au dessus de la normale» de soldats par rapport aux pseudergates. Lorsque la proportion de soldats était «en dessous de la normale», il y a eu inhibition de la production de présoldats de sorte que le développement en présoldats a progressivement diminué à mesure que la proportion de soldats par rapport aux pseudergates approchait de la «normale».Coptotermes formosanus Shiraki peut tolérer et maintenir une proportion remarquablement élevée de soldats (environ 38%), ce qui est bien au dessus de la proportion considérée comme «normale». Un grand nombre (mais pas tous) des soldats en surnombre ont été probablement éliminés par cannibalisme. Des groupes suchargés en soldats ont succombé à la contamination microbienne après que les soldats en surnombre fussent morts de faim.Je conclus de ces résultats que les colonies deCoptotermes formosanus gardent des soldats en proportion constante.
Juvenile hormone III titers and regulation of soldier caste in coptotermes formosanus (Isoptera: Rhinotermitidae).
Juvenile hormone (JH) is an important growth hormone in insects that has also been implicated in caste determination in termites. Gas chromatography-mass spectrometry was used to establish that the JH in the Formosan subterranean termite, Coptotermes formosanus Shiraki, is JH III. JH III titers were measured in workers, pre-soldiers, and soldiers from samples collected from the field. The average titers of JH III in workers and soldiers were about 13 and 25 pg mg(-1), respectively. However, pre-soldiers contained a significantly higher amount, 596 pg mg(-1). As expected, treatment of workers with a JH-analogue, methoprene, triggered rapid formation of pre-soldiers. However, these pre-soldiers had a very low JH III titer (62 pg mg(-1)). It appears that the application of JHA, while inducing pre-soldier formation, does not increase the endogenous JH III titer. The titer, however, increased as the pre-soldiers aged and before transforming into soldiers.
Aggressive behaviour of the harvester termitesHodotermes mossambicus (Hagen) andTrinervitermes trinervoides (Sjöstedt)
Summary1.Individual males, females and pairs of primary reproductives ofH. mossambicus developed strong aggressive reactions to each other after being isolated for approximately 24 hours. The intensity of the reactions was a function of the isolation period. Temperature had no significant influence on the reaction while digging in the soil intensified the reaction.2.Laboratory colonies ofH. mossambicus were only slightly aggressive but field workers from different colonies were strongly aggressive. Use was made of the aggressive behaviour of field workers to determine the area of the foraging territory of a colony. The mean area of 12 colonies was found to be about 1 000 ft2.3.When four laboratory colonies ofH. mossambicus were allowed to coalesce, the resulting colony retained only one pair of reproductives and destroyed the others.4.T. trinervoides colonies collected in the field fought to the death in the laboratory. Workers attacked workers in the absence of soldiers and vice versa.5.H. mossambicus workers and soldiers were not attacked byT. trinervoides soldiers although the two species fought and many individuals were killed when they were forcibly mixed.Zusammenfassung1.Einzelne männliche und weibliche Tiere und Paare der primären Geschlechtstieren derH. mossambicus entwickelten stark agressive Reaktionen gegen einander, nachdem sie etwa 24 Stunden isoliert gewesen waren. Der Grad der Reaktion richtete sich nach der Dauer der Isolierung. Die Temperatur hatte keinen nennenswetten Einfluss auf die Reaktion, während die Tätigkeit des Grabens im Erdboden die Reaktion verstärkte.2.Kolonien derH. mossambicus im Labor waren nur leicht aggressiv, während die Feldarbeiter von unterschiedlichen Kolonien stark agressiv waren. Das agressive Verhalten der Feldarbeiter gab die Handhabe, um den Flächeninhalt des Gebietes, worauf sich die Ernährung der Kolonie stützt, zu bestimmen. Man fand, dass der Flächeninhalt der Gebiet von 12 Kolonien durchschnittlich etwa 1,000 Quadratfuss- 93 Quadratmeterbetrug.3.Beim Vermengen von 4 Laborkolonien derH. mossambicus behielt die daraus entstehende Kolonie nur 1 Paar Geshlechtstieren und vernichtete die andern.4.Kolonien derT. trinervoides, die auf dem Feld gesammelt wurden, kämpften bis zum Tode im Labor. Arbeiter griffen Arbeiter an in Ermangelung von Soldaten und umgekehrt.5.Arbeiter und Soldaten derH. mossambicus wurden nicht von den Soldaten derT. trinervoides angegriffen, obwohl beide Gattungen kämpften und viele Einzeltiere getötet wurden, wenn sie zwangsweise vermengt wurden.