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.
Preliminary studies on the control of caste formation in the harvester termiteHodotermes mossambicus (Hagen)
The control of caste formation in the harvester termiteHodotermes mossambicus (Hagen) was investigated.Normal laboratory colonies contained a primary reproductive pair, between 6.59 and 24.98% workers, 0.39 and 3.45% soldiers and 74.64 and 92.06% larvae. Supplementary reproductives did not develop in colonies deprived of their king and queen. Continuous removal of soldiers stimulated soldier production. We have suggested that a pheromone produced by the soldiers plays a major role in controlling the soldier population of a colony. A similar phermone system appreared to control the production of workers.Evidence was also obtained that the primary reproductive pair influenced the production of workers and soldiers.
Application of resource allocation optimisation to provide profitable options for dairy production systems
A linear program (LP) model analysed resource use on a 100 ha dairy farm. A single optimum-profit combination was established for resources which were either optimised or constrained. It was found that, with a fixed herd of 320 milking cows, when production increased from 305 kg milksolids per cow (kg MS/cow) to 415 kg MS/cow, cash profit increased by 65%. This required additional supplements. If, however, feed demand and supply were optimised at 415 kg MS/cow, the LP reduced milking cow number rather than buy in feed to meet the increased feed demand from higher production per cow. At all production levels chosen between 305 and 415 kgMS/cow, it was most economic to dry off and cull cows early in dry summers to optimise feed demand vs. feed grown; use nitrogen (N) fertiliser to avoid a feed deficit only when response rates of better than 10 kgDM to 1 kg N could be expected; not use N for growing supplements to harvest. Pasture cover, within defined constraint levels, provided a buffer for feed demand and supply fluctuations. The study highlights the importance of assessing production, income and cost in an integrated framework to identify the point at which individual resources become limiting.