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MANFRED D . ENGELMANN
how energetics data could be useful in practical application. Some of the
figures given by Petrides and Swank may be questioned because only a
few observations were represented, but allowing for the paucity of
observations, this remains a stimulating and valuable study.
There are not enough trophic efficiency studies as yet to give a clear
picture of either the structure of communities or the validity of the
Lindeman model. Yet, the data thus far gathered suggest several interesting trends or hypotheses at the population level which could guide
future research. The values determined for several population parameters in various energetics studies have been listed in Table VIII. If
net production and maintenance metabolism are analyzed by using
Spearman rank correlation, there is indicated a relationship, significant
at the 5% level. Yet, when all the data are plotted on a graph (Fig. 2),
only a slight indication of a regression is shown. If, however, the points
are separated with respect to the degree of temperature regulation, data
for poikilotherms reflect a rather clear-cut trend. One point on the graph,
representing information on the harvest ant, P . badius, is far removed
from those of other poikilotherms, the rest falling along a line described
by the following formula: Log R = 62 + 0.86 Log p . (“R” represents
the number of k calories respired by the population found per m2/year
and “p” represents the net productivity in kcal/m2/year.) Slobodkin
(1960) pointed out that in Duphniu after the maintenance requirement was met, the remaining calories went into reproduction, a fact
borne out by this graph. If the data on P. badius are included in the
regression, 0.62 becomes one and the slope changes to 0.55. There is,
however, at least one good biological reason for considering the ant to
be an exception to the usual pattern of energetics found in most animals; namely, the workers, and soldiers are sterile. Although there were
4 000 to 6 000 individuals in a colony, only two were capable of reproducing. One would expect that, when compared with respiratory metabolism, productivity in ants would be low. From the point of view of
energetics, the ant colony is inefficient, burning a disproportionate
amount of energy to produce so little; yet, ants seem to be very successful in the world today. It is of interest to note that the point on Fig. 2
representing data for the ant falls among the group of points representing the data for homiotherms.
The homiotherms, too, apparently burn a disproportionate amount
of energy for what is produced in the way of new protoplasm, a t least by
standards of poikilotherm production. Yet, the homiotherms are also
very successful today. The five points representing the birds and mammals fall along a regression line described by the following formula:
Log R = 2-59 + 1-75 Log p ; “R” and “p” having been previously defined. The regressions for homiotherms and poikilotherms converge, but
MANFRED D . ENGELMANN
how energetics data could be useful in practical application. Some of the
figures given by Petrides and Swank may be questioned because only a
few observations were represented, but allowing for the paucity of
observations, this remains a stimulating and valuable study.
There are not enough trophic efficiency studies as yet to give a clear
picture of either the structure of communities or the validity of the
Lindeman model. Yet, the data thus far gathered suggest several interesting trends or hypotheses at the population level which could guide
future research. The values determined for several population parameters in various energetics studies have been listed in Table VIII. If
net production and maintenance metabolism are analyzed by using
Spearman rank correlation, there is indicated a relationship, significant
at the 5% level. Yet, when all the data are plotted on a graph (Fig. 2),
only a slight indication of a regression is shown. If, however, the points
are separated with respect to the degree of temperature regulation, data
for poikilotherms reflect a rather clear-cut trend. One point on the graph,
representing information on the harvest ant, P . badius, is far removed
from those of other poikilotherms, the rest falling along a line described
by the following formula: Log R = 62 + 0.86 Log p . (“R” represents
the number of k calories respired by the population found per m2/year
and “p” represents the net productivity in kcal/m2/year.) Slobodkin
(1960) pointed out that in Duphniu after the maintenance requirement was met, the remaining calories went into reproduction, a fact
borne out by this graph. If the data on P. badius are included in the
regression, 0.62 becomes one and the slope changes to 0.55. There is,
however, at least one good biological reason for considering the ant to
be an exception to the usual pattern of energetics found in most animals; namely, the workers, and soldiers are sterile. Although there were
4 000 to 6 000 individuals in a colony, only two were capable of reproducing. One would expect that, when compared with respiratory metabolism, productivity in ants would be low. From the point of view of
energetics, the ant colony is inefficient, burning a disproportionate
amount of energy to produce so little; yet, ants seem to be very successful in the world today. It is of interest to note that the point on Fig. 2
representing data for the ant falls among the group of points representing the data for homiotherms.
The homiotherms, too, apparently burn a disproportionate amount
of energy for what is produced in the way of new protoplasm, a t least by
standards of poikilotherm production. Yet, the homiotherms are also
very successful today. The five points representing the birds and mammals fall along a regression line described by the following formula:
Log R = 2-59 + 1-75 Log p ; “R” and “p” having been previously defined. The regressions for homiotherms and poikilotherms converge, but