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Plant Bioregulators in the Metathoracic Glands of Myrmicine Ants.

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[8] This superposition effect is considerably stronger at medium
and high D concentration; the fine structure disappears and the
shifts of the maxima of the lw,ll emission increase with the
donor concentration.
[9] In cases where €\b’i-\g
< EIDA;\ formation of X‘ could
not be detected (e.g. when A = ( I ) , D = tetramethyl-p-phenylenediamine).
[lo] Further details, also regarding complexes with A = ( 2 ) or
(.7j, see G . Briegleb and D . W o l f , to be published.
Plant Bioregulators in the Metathoracic Glands
of Myrmicine Ants[+*]
By Herniunn Schildknecht and Knut Koob [*I
Artu sexdens, t h e leaf-cutting ant, is a highly developed
evolutionary form of the colony-building ants. Its behavior
has been the subject of many investigations,- the chemistry
of its glands, o n the other hand, has been studied in part
only[II, despite the fact that both these topics are closely
interrelated. We were surprised t o learn that the metathoracic
glands contain phenylacetic acid 121 and even more surprised
by the results of a recent analysis of the contents of these
glands that are very sparingly soluble in water.
Pure secretion from 60 glands could be separated by thinlayer chromatography on silica gel G F (Merck) in petroleum
ether/ether/acetic acid (67 : 30 : 3) into two fluorescencequenching zones, that nearer the front (Rf = 0.5) being due
to phenylacetic acid and the other (Rf == 0.3) to a n unknown
substance. Since this unknown substance rapidly decomposed
with discoloration from pink to brown we isolated it from a
metathoracic extract obtained from a 40 g quantity of ants by
column chromatography o n Sephadex (LH20). According t o
its UV spectrum and its reaction with van Urk’s reagent 131
the unknown substance had to be an indole derivative.
Polarity of the molecule suggested the presence of a carboxyl
group; since the acid itself readily decomposed, the methyl
ester was isolated, purified, and identified.
Of the many substances used for comparison with the gelchromatographically isolated unknown component only 3-
indolylacetic acid had the same Rf value and exhibited the
same color reaction and UV absorption. Furthermore, we
were able t o identify the corresponding fraction, obtained by
column Chromatography in the esterified secretion as methyl
3-indolylacetate, mass spectrometrically. Quantitative UV
spectrometry showed that each gland contained
to
5 Y 10-7 g or 5.7 :: 10-10 to 2.8 >~ 10-9 mole of 3-indolylacetic acid; this corresponds t o a 1--6% solution of 3-indolylacetic acid in the glands.
We have also detected 3-indolylacetic acid in the ant
Myrmica luevinodis. This finding is very interesting because
the myrmicine ants gather their food for wintert41 as did
primitive men earlier. The leaf-cutting ants go one step
further - they cultivate fungi (51. The “collectors and growers”, therefore, very probably learned much earlier than man
to breed growing things and then store them as food. The
heteroauxin 3-indolylacetic acid not only influences growth
but also hinders seed germination 161. We now wish to ascertain whether the phenylacetic acid and 3-indolylacetic acid
act synergistically 171.
IZ 140 IE]
German version: Angew. Chem. 82, 181 (1970)
Received: January 15, 1970
[*I Prof. Dr. H. Schildknecht and Dipl.-Chem. K. Koob
Organisch-Chemisches Institut der Universitat
69 Heidelberg, Tiergartenstrasse (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft. We thank Prof. Dr. X. Cosswald, Wiirzburg, for
the supply of leaf-cutting ants.
[l] A . Butennndt, B. Linzen, and M . Lindauer, Arch. Anat.
microsc. Morph. exp. 48, 13 (1959).
[2] U . Masrhwitz, K . Kooh, and H . Schildknecht, Insect Physiol. 16, 387 (1970).
[ 3 ] E . Stnhl and H. Kaldeney, Hoppe-Seylers Z. physiol. Chem.
323. 182 (1961).
[4] Proverbs 6, vv., 6-8.
[ 5 ] H. Mnrkt in: Grzimeks Tierleben, Enzyklopadie des Tierreiches. Kindler Verlag, Zurich 1969, Vol. 11, p. 503.
161 W. Sexton: Chemische Konstitution und biologische Wirkung. Verlag Chemie, Weinheim 1958, p. 364.
[7] Cf. [61, p. 379.
C O N F E R E N C E REPORTS
Structural Chemistry of Refractory Metallic
Compounds
By H . Nowotny[*I
The compounds having the highest melting points known so
far, H f C and TaC, belong t o the structurally simple transition
metal (T) monocarbides. Although many of these compounds
are nonstoichiometric, due t o a carbon deficiency, the
vacancies (and the carbon atoms) nevertheless exhibit some
degree of order[Il. This order is even more pronounced in the
subcarbides TzC, which were previously generally regarded
as hexagonally close-packed metal host lattices having a
random distribution of carbon atoms. In fact a series of
ordered structures is now known, e.g. the anti-Cdlz, C-FezN,
or 5-Nb2C types, which all exhibit an unequal T-C-T
and
T-vacancy-T distance. This emphasizes the significance of the
octahedral structural unit [T&I. It is remarkable that similar
structural principles are encountered in transition metal
carbide hydrides. Thus, ZrzCH can be regarded as an interstitial compound of hydrogen with a Zr2C host lattice (antiCdIz type).
Angew. Chem. internat. Edit.
/ Vol. 9 (1970) 1 No.
2
A large number of carbides, which are formed, e.g., by the
action of a further transition metal or of a meta-metal on T C
or TzC, yield a uniform class, in which the octahedral unit
dominates; inclusion of other small nonmetal atoms and the
trigonal-prismatic structural unit extends this class considerably. This classification naturally also permits inclusion of
long-known complex carbides and related compounds such
as the ?-carbides in high-speed tool steels and the ?-oxide in
ferrotitanium. Linkage of the [T6x1 octahedra via corners
leads t o the perovskite carbides, e.g. TisAIC, or to the filled
U3Si type, e.g. Cr3AsN, or to the filled p-Mn type, e.g.
MO~AI~C
etc.
, Linkage of the [T6X] octahedra via edges
produces the H phase, e.g. CrZAIC, or the Ti3SiC2 type, etc.
Common features become apparent regarding the components and the composition in agreement with the structural
units: e.g. the H phase V2PC can be considered as the sum of
the two kinds of building units [VCI-octahedra
[VPI-trigonal-prisms, which are already present in the binary compounds; similarly, MozBC is built up from the structural
elements occurring in the cubic form MoCl-, and MOB.
+
There are good reasons for assuming that the metallic host
lattice is mainly responsible for the high stability of carbides,
173
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