Dorylus (Anomma) wilverthi Emery
Type locality Zaïre (Emery, 1899e: 459, illustrated,
worker; also in Emery, 1901c; Forel, 1909b: 51, male) from
Kinshasa [Leopoldville], collected by Wilwerth; junior synonyms
nigritarsis (Strand, 1911: 118, queen) from Cameroun,
nomadas (Santschi, 1935a: 254, queen, illustrated,
synonymy by Raignier & van Boven, 1955) from Zaïre;
and sjostedtiwilverthi (Anomma sjostedti var sjostedtiwilverthi,
Wasmann, 1916: 136; 1917: 305, worker; new synonymy, see below)
from Cameroun; all forms known (see Bolton, 1995)
.
Emery's (1899e) description is at
;
Emery's (1901c) illustrated description is at
;
A set of illustrations of the queen and workers by Forel (1912j)
is at ;
Santschi's (1935a) illustrated description of nomadas
(queen) is at
.
Emery's description was quoted in full by Raignier & van
Boven, 1955). My summary translation is - "Head, vis-a-vis
arcens, less elongated, sides less arcuate and the
posterior angles each prolonged into a raised point, slightly
recurved outwards; these points are present in all morphs but are
strongest in the media. Posterior of head deeply scalloped in an
arc. The elongation of the head is especially remarkable in the
small examples which have the same modifications of the clypeus
and pubescence of all the Anomma".
Forel (1909b) describing a male collected by M. Luja in company
with "A. wilwerthi" workers, had - TL 26-30 mm,
more red and larger than that of nigricans, with longer
and narrower mandibles; the vertex also is a little more "bombé"
- bulging or convex. |
I
have to say that I am baffled by the notes and illustration in
Emery (1901c) of what he reported as minima morphs with TL 3 mm
and 9 antennal segments and TL 2.5 mm and 8 antennal segments
respectively. Among the various species I have seen and
photographed, there does not appear to be any minima with less
than 11 segments to the antenna. Emery gave no collection details
and it seems possible that the single specimen of each morph are "contaminants",
perhaps being Dorylus
(Alaopone) antinorii - as shown by Emery himself (1881a)
but transferred by me to Alaopone.
Wheeler (1922) had full-face illustrations of the head of the
soldier and a minor worker, showing the characteristic elongated
and divergent posterior corners of the head (right, drawing
apparently somewhat exaggerated). |
Also
from Ivory Coast, at Ouossou (Talbot, in Wheeler, 1922).
Forel (1909b) reported workers from Kinshasa [Leopoldville] by
Lamarche, and Iringui by Lindemans. He also noted a male, TL
26-30; from Mobeka, by Lothaire, being redder and larger than that
of nigricans, with the mandibles slightly longer and
straighter, also the vertex slightly more convex, bulging, the
specimen was found with workers of "wilwerthi".
Bolton (1995) notes that the name is frequently misspelt as wilwerthi
but the real error seems to lie in a misspelling, by Emery
(1899)?, of the name of the collector who seems definitely to have
been Wilwerth; although later in his paper, Forel (1909b)
writes of "Plagiolepis fallax" as collected by
E. Wilverth. Towards the end of the same paper, Forel,
notes how, in August 1907, Luja collected the male with workers on
the same army, providing confirmation that his (Forel) description
of the male was correct.
It appears to be a forest species, commonest or even restricted
to areas of relatively low insolation, which gives for great
geographical scope in the Congo Basin, etc.Raignier & van
Boven (1955) found it to be by far the most common Anomma
species at Yangambi in Zaïre; making 26 collections,
from 19 nests, with a total of 568 individuals. Their photographs
of the head of the major morph are shown below right.
Although they also reported two collections of sjostedtiwilverthi,
I suspect from the notes they give of the colonies being mixed,
with predominantly normal wilverthi specimens but a
relatively small number with reduced or absent teeth on the
posterior corners of the head, that what happens is that their
findings, and the single finding reported by Wasmann (from Grand
Batanga, Cameroon), represent no more than aberrant individuals of
a standard wilverthi colony.
Wasmann himself (1916: 136) simply noted - "Ein exemplar
lag vor, von Geo Schwab bie Groß-Batang in Kamerun 11.7.1912
in einem Zuge von Anomma sjöstedti Em. var. Sjöstedti-Wilverthi
(einer Übergangsform zwischen diesen beiden Rassen) gefangen.
Ich bennene die Art zu Ehren des Entdeckers".
Of course, one cannot rule out the occurrence of a hybrid "species".
Bolton (1995) has - "Subspecies of nigricans: current
status" without giving any authority. |
A series of worker sizes is illustrated in Schneirla (1971, page
25), as ranging from TL 11.2 mm down to 3 mm. The queen may be TL
52 mm, and lay some 1-2,000,000 eggs in her lifetime. The same
author (largely extracting from Raignier & van Boven, 1955)
described the colony size as 10-20 million, with a single queen.
The nest was said to be within 1-2 m below ground, often under the
roots of trees with a central mass. (see illustrations from
Wheeler, 1992, "click" left"). Raiding takes place
at dusk, less often at dawn and never at midday. Emigration took
place most frequently every 25 days or so, although a stay could
be as long as fifty days. The average of 26 migrating columns
showed a travel of 226 m, said to be the longest of all dorylines,
with the movement time averaging 34-38 hours, up to 57 hours in
duration. The effect of the movement results in a trench of
notable depth, effectively keeping the column below ground.
Raignier & van Boven (1955) have full descriptions of the
worker major, male and queen; with specimens of all from within
one nest and so definitively associated, unique (at least when
they wrote) for all known species of Anomma. They included
photographs (monochrome) of the male and female and these are
reproduced here. |
Full
description of major worker (translated from Raignier & van
Boven, 1955)
Overall - head brown-black; mandibles, antennae and clypeus
red-brown; thorax, petiole and gaster red to red-brown;
subpetiolar process dark brown-black; gaster with black areas.
TL 12.38 HL 3.72 HW 3.64 HD 2.60 CI 98 SL 2.04 SI 55 AL 4.11 PW?
PetL 1.13 PetW 0.92 GL? MFL ?
Head - widest at anterior; posterior border scalloped, posterior
angles extended and with a small lateral turned tooth
(characteristic of the species); median line a somber suture on
the occiput, becoming a small groove on the vertex; occiput,
vertex and front shiny, @ 50 X light reticulation is visible with
very sparse puncturation; clypeal margin recurved, with several
long hairs, central hairs five times longer than others; mandible
slender and with apical tooth;basal tooth set just behind the
midpoint, no subapical teeth but internal border crenulated and
with hairs, external border glabrous and very finely reticulate;
central notch small but visible between frontal carinae and
vertex; scape slender (width about 1/8 of length) and slightly
curved, finely spiculated (recouvert de réticules
chitineux) and with fine pilosity, apex enlarged with several
erect hairs; funiculus punctuate all over and with tiny erect
hairs, segment 2 slightly shorter than 1; 3-5 equisized, slightly
longer than 6-9, 10 a club more than twice length of 9; in profile
height 70% of length.
Alitrunk - from above much narrower than the head; finely
puncturate; metanotal groove distinct but mesonotum barely
distinguishable from the propodeum; towards outer edge of
propodeum there is a feeble depression giving rise to divergent
edges of the declivity; in profile metanotal groove sharp,
pronotum slightly above mesonotum; spiracle large; metanotal gland
with prominent upper flange terminating in a tooth.
Petiole - from above narrowed anteriorly, longer than wide,
puncturate and with several hairs, posteroventral processes small
(but not a consistent feature among colonies); laterally height
about 60% of length, spiracle well developed and raised;
subpetiolar process "scyphiforme" (variable in form and
not a reliable diagnostic character) with long hairs.
Gaster - five segmented, overall shape oval; terminal borders
with long hairs; basal half of first segment glabrous and shiny;
sternites with long hairs.
Legs - coxae finely puncturate; femora glabrous but with golden
pubescence; same on tibiae; tarsi with oblique erect hairs; total
length of hind legs 13.86 mm. |
Polymorphism
In October 2003, Professor Shigeo Uehara sent me three samples of
wilverthi from the Kalinzu Forest, Uganda, these
were - III-85, of 19.xi.2002, W. of 519, in forest; III-89, of
19.xi.2002, W. of 430 (T4), in forest; III-137, of 23.xi.2002,
Sawmill, in forest. From those I was able to create this
polymorphism montage and the other photomontages. What is unusual
is that the all the morphs, even the very smallest, have the
posteriorly narrowed head, with distinct dorsolateral points.
The various morphs are shown in detail on
Dorylus (Anomma)
wilverthi page. |
|
|
Photomontage
(right) of worker media, possibly 3, from -
http://www.antweb.org/specimen.do?name=casent0401751
Collection details - Central African Republic: Prefecture
Sangha-Mbaéré; Parc National Dzanga-Ndoki, Mabéa
Bai, 21.4 km 53° NE Bayanga; 03°02'00"N 016°24'36"E,
510m. Collection Information: Collection codes: BLF4000. Date: 1-7
May 2001. Collected by: B.L.Fisher. Method: EC19 sifted litter.
Habitat: rainforest. Transect Type: MW 50 sample transect, 5m
Transect Sample No.: 29. |
Sexual
stages -
Forel (1909b) describing a male collected by M. Luja in company
with "A. wilwerthi" workers, had - TL 26-30 mm,
more red and larger than that of nigricans, with longer
and narrower mandibles; the vertex also is a little more "bombé"
- bulging or convex. |
|