Lasius (Lasius) neglectus, Loon & Boomsma & Andrasfalvy, 1990

Loon, A. J. Van, Boomsma, J. J. & Andrasfalvy, A., 1990, A New Polygynous Lasius Species (Hymenoptera; Formicidae) From Central Europe, I. Description and General Biology, Insectes Sociaux 37, No. 4, pp. 348-362 : 350-360

Lasius (Lasius) neglectus spec. nov.

Diagnosis

(comparisons are made with L. alienus from western and central Europe).

WORKER

Similar to L. alienus , but slightly smaller on average and by range ( table I ; fig. 2 ); body colour slightly paler brown. Clypeus not or only slightly keeled ( L. alienus with slight but still rather more clearly defined keel on clypeus). Mandible nearly always with 2 basal teeth ( fig. 5A ), only very exceptionnaly with 3 teeth ( L. alienus has 3 basal teeth, fig. 5E ). Scapes and fore tibiae completely without standing hairs. Standing hairs on alitrunk clearly shorter than in L. alienus (cf. fig. 5B and 5F ).

QUEEN

Much smaller than L. alienus ( table I ; fig. 3 ). Body colour dark brown, legs and scapes paler brown. Body clearly darker and less reddish brown than L. aIienus. Scapes and fore tibiae without standing hairs. Head and alitrunk covered with standing hairs. Wings hyaline, not infuscated.

MALE

Much smaller than L. alienus ( table I ; fig. 4 ). Body colour dark brown, legs paler brown. Body clearly darker and less reddish brown than L. alienus . Scapes and fore tibiae without standing hairs. Head and alitrunk sparsely covered with standing hairs. Wings hyaline, not infuscated. Subgenital plate without protruding lobes (cf. fig. 5C and 5G ). Sagitta with 10-17 teeth (cf. fig. 5D and 5H ). (See also drawings of other Lasius species in BERNARD, 1968 and KUTTER, 1977).

The species is further characterized by the fact that it is polygynous, by its pattern of allozyme variation ( BOOMSMA et al., 1990), and by the huge numbers of workers involved in tending and feeding on aphids and scale insects in trees (much more conspicuous than in other Lasius s. str. species, even L. brunneus ).

Using recent keys (e.g. AGOSTI and COLLINGWOOD, 1987 for workers, KUTTER, 1977, BERNARD, 1968), all castes of L. neglectus would be identified as L. alienus . It should be noted that Lasius- " species 1 " in AGOSTI and COLLING- WOOD (1987) refers to workers of yet another species, collected in eastern Austria by J.J. BOOMSMA; it is a very dark alienus-like species, but again with a distinct allozyme pattern (BOOMSMA et al.. 1990). It was also found in 1988 in Budapest. Awaiting the collecting of sexuals, this species will be further dealt with in a later paper. -

Description

WORKER

Body length 2.5-3.5 mm; further measurements in table I .

Colour: body brown, unicolorous (sometimes head and gaster only slightly darker than alitrunk). Antennal scapes pale brown, funiculus gradually darkening towards tip. Legs: coxae and femora brown (like body), tibiae and tarsi paler brown, contrasting with the rest of the body.

Hairs: head, alitrunk and gaster covered with standing hairs, rising above the general pubescence, but especially on alitrunk short; scapus and fore tibiae without standing hairs, pubescent only; middle and hind tibiae may have an occasional standing hair.

Head: surface as alitrunk; occipital border, when viewed in perfect full face, more or less straight, neither clearly convex nor concave; frontal groove indistinct; ocelli small, indistinct on mounted specimens, but clearly visible on specimens preserved and viewed in alcohol; clypeus not or only very slightly keeled; maxillary palp rather long, three terminal segments equal in length; mandible with two basal teeth ( fig. 5A ; only very rarely three teeth).

Alitrunk: surface rather smooth, only finely reticulate, not very sculptured.

Petiolus: similar to L. alienus , dorsal border in frontal view slightly emarginate, in profile slightly thicker on anterior side than alienus .

QUEEN

Body length c. 6 mm; other measurements see table I.

Colour: body dark brown to blackish brown, unicolorous or gaster only slightly lighter brown; when viewed in alcohol, the body appears brighter brown. Antennal scapes yellowish brown, funiculus gradually darkening towards tip. Legs: coxae and femora brown, slightly paler than body, tibiae and tarsi yellowish brown.

Hairs: head, alitrunk and gaster covered with standing hairs rising above the general pubescence; scapus and tibiae without standing hairs, pubescent only.

Head: surface as alitrunk; occipital border, when viewed in perfect full face more or less straight, or only slightly concave; head width narrower than maximum width of thorax; clypeus not keeled.

Alitrunk: surface varying from rather smooth, only finely reticulate, to strongly sculptured (this may vary within nests); wings completely hyaline, only veins brown or yellowish brown.

Petiolus: similar to L. alienus ; rather narrow in profile, in frontal view rather broad and dorsal border clearly emarginate.

MALE

Body length 2.5-3.5 ram; other measurements see table L

Colour: body dark brown to blackish brown, unicolorous or gaster slightly duller and paler brown. Antennal scapes dark brown, as head, funiculus yellowish brown (not gradually darkening towards tip). Legs: coxae, femora and tibiae brown, slightly paler than alitrunk, tarsi yellowish brown.

Hairs: head, alitrunk and gaster sparsely covered with standing hairs, rising above the general pubescence; scapus and tibiae without standing hairs, pubescent only.

Head: surface as alitrunk; occipital border convex, sometimes plane of two posterior ocelli just projecting from border, occipital corners curving into sides of head; clypeus not keeled: mandible of "niger-type " (cf. WILSON, 1955).

Alitrunk: surface rather smooth, only finely reticulate, not strongly sculptured; wings completely hyaline, veins hardly coloured.

Petiolus: similar to L. alienus ; rather short and thick in profile, in frontal view dorsal border slightly emarginate.

Gaster: subgenital plate without protruding lobes ( fig. 5C ).

Genitalia: sagitta with 10-17 teeth.

Type designation

HOLOTYPE:

Winged queen (mounted), garden of the Company for the Development of Fruit and Ornamental Production , Park utca , Budatétény (Budapest), Hungary, 24 June 1988, leg. AJ. VAN LOON.

PARATYPES:

(From the same nest as the holotype): 6 queens, 3 males and 4 workers (all mounted); other paratypes: 2 queens (mounted) from nest 5, same locality, 7 July 1988; 4 queens, 23 males, and many workers and pupae (all preserved in alcohol) from nest 3, same locality, 1 July 1988. The holotype and the paratypes are deposited in the collection of the Institute of Taxonomical Zoology (Zoological Museum), Amsterdam (ZMA). Other specimen series are deposited at the Rijksmuseum van Natuurlijke Historie, Leiden, the Netherlands (nest 5), and at the Natural History Museum, Budapest, Hungary (nest 8, 12 and 16). Remaining specimens from the type-nest, both mounted and preserved in alcohol, are in the private collection of A.J. VAN LOON.

Derivation of name

The new species is named after its rather late discovery, apparently being unnoticed for some time. We would like to add the following remarks: T wo Lasius taxa, synonymized with L. alienus by WILSON (1955), have been reported from approximately the same Budapest districts: L. alienus var. pannonica RÖSZLER, 1942 (RÖSZLER, 1942, fide STARCKE, 1944), and L. alienus lasioides ( EMERY, 1869) ( EMERY, 1869; see also WILSON, 1955). Reasons why these names are considered to refer to other ants, and thus not to be available for the present species, are as follows: Judging from the description from RÖSZLER, workers and queens of pannonica are quite distinct from those of L. neglectus , despite their similar size. Type-material of pannonica could not be studied, as the types were lost during World War II (cf STARCKE, 1944, WILSON, 1955). L. alienus lasioicles was described by EMERY from Naples, Italy. Later rather heterogenous material from several European localities was attributed to this name, and descriptions from various authors differ highly (cf. ZIMMERMANN, 1934; STITZ, 1939; STÄRCKE, 1944). The original description of Emery states that the queens have dearly infuscated wings, which are clearly not so in L. neglectus . Material from Budapest, identified as lasioides by STÄRCKE (1944), clearly differs from L. neglectus (Stärcke collection, Rijksmuseum van Natuurlijke Historic, Leiden, The Netherlands); it may be the same taxon as the dark " alienus "-like, allozymatic distinct form mentioned above (species 1 in AGOSTI and COLLINGWOOD, 1987 and BOOMSMA et al., 1990).

L. niger lasioides vat. barbara SANTSCHI was described from northern Africa (SANTSCHL 1921), and synonimized with L. alienus by WILSON (1955). We have studied the mounted lectotypes and other specimens (workers only) from the Santschi-collection (Naturhistorisches Museum, Basel, Switzerland) and some alcohol-preserved material (all castes, collected by Dr. H. CACNIANT in Algeria, June 1965). Although only few specimens could be examined, we consider barbara distinct from L. neglectus on account of the following characters:

Workers: Slightly but consistently larger than L, neglectus in all measurements. Mandibles and hairs on alitrunk as in L. neglectus (see description).

Queens: Similar in size to L. negtectus . When viewed laterally, the petiolus has a broader basis, thus appearing shorter and thicker than in L. neglectus .

Males: Larger than L. neglectus in all measurements. Same petiolus difference as in queens. Subgenital plate superficially similar to L. neglectus , but posterior edge distinctly more curved (cf. fig. 5C and 5I). Sagitta with 12-18 teeth. Both the mounted dry specimens and the alcohol-specimens of barbara are now clearly lighter and browner than west - and central - European L. alienus (and L. neglectus !), contrary to statements made by SANTSCHI (1921) in the original description (" nearly black "), and contrary to WILSON (1955: " darker than alienus "). Although coloration in preserved specimens may be lost to some degree as time proceeds, this discrepancy is remarkable.

Measurements

Measurements of L. neglectus , and the related L. alienus and L. brunneus , and correlations between body size variables are presented in tables I and II and figures 2 - 4 . The morphological similarity of the workers of L. neglectus to L. atienus is evident from these data. Although L. neglectus is smaller on average, ranges overlap and the principle axes of correlation between HW and PW are very similar ( table II , see also fig. 2A ). More scatter was found in the correlation between SL and HW, but the correlation axes of L. neglectus and L. alienus are still very close ( fig. 2B , the SL/HW ratio in table I and data in table II ), the divergence being caused mainly by two outlying points. L. brunneus is clearly separated by its broader head (cf. SL/HW ratio in table I and fig. 2B ).

The queens and males of all three species are distinctly separated in the correlation diagrams ( fig. 2 and 3 ), as is also obvious from the data in table I .

Distribution and ecology

At present, L. neglectus is only known from Budapest. The boundaries of the 1988 distribution in the surroundings of the type locality are shown in figure 1, and were estimated to cover an area of ± 2 km². It is mainly a suburban habitat of houses with gardens, apartments and office blocks, streets bordered by trees, and small parks, with hardly any natural or seminatural vegetation. Some isolated occurrences just outside this area are indicated on the map as well. These are likely to be the result of human transport of potted plants from the research institute, containing neglectusqueens. Another isolated locality, further away, is situated in the garden of the Budapest Historical Museum, on the southern side of the Várhegy (Castle District), in the centre of Budapest ( fig. 1 ). Workers were found in massive numbers on only one tree and around decorative potted laurel trees; these laurel trees used to be hibernated in the greenhouses of the research institute, and are thus believed to have been the vectors by which L. neglectus reached this new locality, where it is certainly not very abundant yet. A second remote and isolated locality has been found in eastern Budapest (Petervárád utea and surroundings). How L. neglectus reached this locality is at present unknown.

At and around the type locality, nests have been found in various places, mostly under stones, in rocky soils and under and in man-made structures like houses, pavement edges, but also in grassy slopes, among tree-roots, and even in barren solid soil. No clear mounds were found. Colony boundaries appeared to be diffuse or non-existant. The polygyny of L. neglectus was demonstrated by digging in easily accessible nests: in this way several dealated active queens were usually found in the same burrow. On 24 June 1988 two copulas were observed in one nest, showing that intra-nidal mating occurs. Also freshly dropped wings of queens were regularly found within nests, suggesting the immediate re-adoption of intra-nidally inseminated queens. Although the alate sexuals were sometimes present on or just below the soil surface, a clear nuptial flight was never observed, neither in 1988 nor in the previous 15 years. (A. Andrfisfalvy, unpublished records and interviews with inhabitants of the area). From 10 July onwards no winged sexuals were found anymore.

L. neglectus appears to be a very opportunistic species occupying all available nest space and monopolizing virtually all trees for tending and harvesting aphids. Especially in the centre of its distribution, near the type locality, virtually all other ant species have disappeared during the last 15 years.! The former ant-fauna in the garden of the research institute included at least the following species: Messor structor , Tetramorium spec. , Diplorhoptrum fugax , Lasius niger , Formica cinerea , F. rufibarbis and Polyergus rufescens . In 1988 only two small nests of M. structor , two of Tetramorium , two of D. fugax , and one nest of L. umbratus were found, and some foraging workers of F. cinerea and/ or rufibarbis and Camponotus piceus . Near the edges of the distribution, and in older, somewhat more diverse small parks within the main range, other species were found as well: L. niger , L. emarginatus , L. brunneus , F. rufibarbis and/ or cinerea (regularly), and Prenolepis nitens , L. fuliginosus , Plagiolepis pygmaea , Camponotus vagus , C. truncatus and Dolichoderus quadripunctatus (more rarely).

Figures

Fig. 1. - Distribution in 1988 of Lasius neglectus in Budapest. Legend: * isolated locality (3 just outside main range, 2 on the inset in the centre of the city); ----- - estimated border of distribution; T = type locality. Fig. 1. - Distribution en 1988 de Lasius neglectus 5. Budapest. Légende: * localité isolée (3 juste au dehors de la distribution principale, et 2 sur la carte du centre de la ville); --- --- frontière estimée de la distribution; T = localité typique.

Fig. 2. - Correlation of morphological variables in workers: (A) between HW and PW, (B) between SL and HW. Fig. 2. - Corrélation des variables morphologiques chez les ouvrières: (A) entre HW et PW, (B) entre SL et HW.

Fig. 3. - Correlation of morphological variables in queens: (A) between HW and PW, (B) between SL and HW. Fig. 3. - Corrélation des variables morphologiques chez les femelles: (A) entre HW et PW, (B) entre SL et HW.

Fig. 4. - Correlation of morphological variables in males: (A) between HW and PW, (B) between SL and HW. Fig. 4. - Corrélation des variables morphologiques ch~z les mMes: (A) entre HW et PW, (B) entre SL et HW.

Fig. 5. -- Lasius neglectus. (A) mandible of worker; (B) alitrunk of worker; (C) subgenital plate of male; (D) sagitta of male; (E-H) same for L. alienus; (I) subgenital plate of ~barbara~-male. Fig. 5. - Lasius neglectus. (A) mandibule de l'ouvri~re; (B) thorax de l'ouvri6re; (C) plaque sous-g6nitale du mille; (D) sagitta du mille; (E-H) les m6mes pour L. alienus; (I) plaque sous-g6nitale du m~le de,~ barbara ~.

Tables

Table I. -- Measurements of Lasius neglectus, L. alienus and L. brunneus. Maximally 3 - individuals per colony are included. Average (avg), standard deviation (sd), sample size (n), and range (min-max) are given. HW = head width, HL = head length, PW = pronotum width, SL = scapuslength, all in mm. Tableau I. -- Mesures de Lasius neglectus, L. alienus et L. brunneus. On a mesur6 un maximum de 3 individus par colonie. Moyenne (avg), d6viation standard (sd), nombre d'individus (n), et valeur minimale et maximale (min-max) sont donn6s (routes en mm). HW = largeur de la t6te, HL = longueur de la t6te, PW = largeur du pronotum, SL = longueur du scape.

WORKERS	HW	HL	HW/ HL	PW	SL	SL/HW
L. neglectus
avg	0.75	0.82	0.91	0.50	0.75	1.01
sd	0.03	0.03	0.02	0.02	0.03	0.03
n	63	63	63	63	63	63
min	0.64	0.72	0.89	0.43	0.68	0.96
max	0.81	0.88	0.99	0.56	0.80	1.06
L. alienus
avg	0.81	0.87	0.93	0.55	0.81	1.01
sd	0.06	0.05	0.03	0.04	0.04	0.05
n	36	36	36	36	36	36
min	0.68	0.75	0.88	0.46	0.72	0.88
max	0.92,	0.97	1.02	0.60	0.89	1.12
L. brunneus
avg	0.93	0.95	0.96	0.60	0.80	0.87
sd	0. i0	0.07	0.02	0.07	0.06	0.04
n	31	16	16	31	31	31
min	0.75	0.84	0.93	0.48	0.68	0.80
max	1.18	1.07	1.01	0.76	0.94	0.97
QUEENS	HW	HL	HW/ HL	PW	SL	SL/HW
L. neglectus
avg	1.34	1.20	1.12	1.54	1.03	0.77
sd	0.03	0.03	0.02	0.07	0.02	0.02
n	17	17	17	17	17	17
rain	1.27	1.16	1.08	1.41	0.99	0.72
max	1.39	1.24	1.17	1.68	1.07	0.81
L. alicnus
avg	1.61	1.42	1.13	1.93	1.20	0.75
sd	0.05	0.03	0.03	0.04	0.03	0.03
n	13	13	13	13	13	13
rain	1.56	1.38	1.09	1.84	1.15	0.70
max	1.70	1.46	1.20	1.98	1.23	0.79
L. brunneus
avg	1.64	--	--	1.61	1.11	0.68
sd	0.03	--	--	0.05	0.03	0.02
n	9	--	--	9	9	9
rain	1.58	--	--	1.53	1.08	0.65
max	1.69	--	--	1.68	1.15	0.71
MALES	HW	HL	HW/ HL	PW	SL	SL/ HW
L. negIectus
avg	0.71	0.62	1.15	0.62	0.46	0.65
sd	0.04	0.03	0.02	0.04	0.02	0.03
n	23	23	23	23	23	23
rain	0.68	0.59	1.10	0.59	0.41	0.56
max	0.80	0.68	1.19	0.72	0.51	0.70
L. alienus
avg	0.89	0.72	1.24	0.89	0.59	0.66
sd	0.04	0.03	0.03	0.03	0.03	0.02
n	12	12	12	12	12	12
rain	0.81	0.67	1.19	0.83	0.54	0.61
max	0.95	0.77	1.29	0.94	0.62	0.70
L. brt .tnneus
avg	1.10	m		0.99	0.68	0.62
sd	0.04	M		0.04	0.03	0.02
n	9			9	9	9
min	1.05			0.93	0.65	0.58
max	1.15			1.04	0.73	0.64

Table II. -- Product-moment correlation (SOKALand ROHLF, 1981) between morphological variables in workers of L. neglectus, L. alienus, and L. brunneus. Given are the correlation coefficient (r), the equation of the principe axis, and 95% confidence limits to the slope of the principal axis. Tableau II. -- Correlation (SOKAL et ROttLF, 1981) entre variables chez les ouvri~res de L. neglectus, L. alienus et L. brunneus. Le coefficient de corr61ation (r), l'6quation de la droite de corr61ation, et les limites de confiance /i 95 % de l'inclinaison de l'axe principal sont donn6s.

	principal axis			r	95%	conf. limits
HW against PW L. neglectus L. alienus L. brunneus	HW = 1.52 PW HW = 1.48 PW H-r162= 1.51 PW	-- + +	0.01 0.01 0.02	0.88 0.95 0.%		1.32- 1.76 1.31- 1.67 1.39- 1.64
I.,SL against HW " L. neglectus L. alienus L. brunneus	SL = 0.83 HW SL = 0.66 HW SL = 0.63 HW	+ + +	0.13 0.26 0.22	0.84 0.81 0.93		0.70 - 0.98 0.50 - 0.86 0.55 - 0.73