Short Communication |
Corresponding author: Wojciech Czechowski ( w.czechowski3@upcpoczta.pl ) Academic editor: Petr Klimeš
© 2019 Wojciech Czechowski, Gema Trigos-Peral, István Maák, Kari Vepsäläinen.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Czechowski W, Trigos-Peral G, Maák I, Vepsäläinen K (2019) Alate gyne of the ant Dolichoderus quadripunctatus (L.) follows foraging trail to aphids (Hymenoptera, Formicidae). Journal of Hymenoptera Research 71: 241-248. https://doi.org/10.3897/jhr.71.36286
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The first observation of alate gyne of Dolichoderus quadripunctatus (L.) visiting aphids is described. A gyne walked along a foraging trail to the aphid Panaphis juglandis Goeze colony where it imbibed honeydew excreted on the leaf by the aphids, after which it returned to the trail. This recurred during two more days, always a single alate gyne at a time; hence the total number of gynes, one or more, remained open. The phenomenon, hitherto practically unknown in ants, is presented against the background of the biology of the species and discussed in the context of specific environmental circumstances and the colony dynamics.
Ants, aphids, behavioural plasticity, colony dynamics, gyne foraging, life history, Panaphis juglandis
In ants and other social insects, the basic division of tasks is such that workers take care of the colony tasks, whereas queens reproduce (
Here, we report our observations on this previously practically unknown behaviour, foraging of one or more alate ant gynes [though see Discussion on the microgynes of Manica rubida (Latr.)], and discuss it in a wider context of the biology and life history of the species in question, Dolichoderus quadripunctatus (L.).
Observations were made in the area with sparse single-family housing in Brwinów (52°08'N, 20°43'E) near Warsaw, Poland. The site of observation was in a garden growing, among others, a few common walnut trees (Juglans regia L.) next to a detached house with old wooden elements (elevation, pillars, balustrades) (Fig.
At the beginning of July 2017, a colony of nymphs of the large walnut aphid Panaphis juglandis Goeze appeared on a leaf of a young walnut tree, on its upper surface, at a height of 1.1 m above the ground. On July 7, the aphids were discovered by D. quadripunctatus foragers from a nest in a wooden terrace pillar at a height of c. 4.5 m above the ground (Fig.
On July 16, an alate D. quadripunctatus gyne appeared at the aphids (Fig.
At the end of July, a ladybird (Adalia bipunctata L.) appeared at the aphid colony. Within three days, without being counteracted by the ants, it ate all the aphids. In the following days also the other two colonies of P. juglandis were consumed, which put an end to the observations. The lack of defense of the food resources by D. quadripunctatus was also revealed by multiple observations of the syrphid fly which, not disturbed by ants, licked the honeydew in the immediate vicinity of them. Concurrently, elsewhere in the garden, D. quadripunctatus foragers used experimentally placed baits with diluted honey, but withdrew on the appearance of Lasius niger (L.) workers.
The foraging trail along which the alate gynes walked to the aphid colony on the young walnut, led, inter alia, through the trunk and twigs of a black elder (Sambucus nigra L.) shrub. The critical point of the route was the passage from the elder leaf to the handrail of the stairs (Fig.
Foraging of inseminated dealate young gynes is not uncommon in ants. It is the norm in a lot of species which found new colonies semi-claustrally (e.g.
In Dolichoderinae, foraging of queens is scarcely documented. It was only recently documented within the genus Technomyrmex Mayr which includes many tramp species; ergatoid (worker-like) queens of T. vitiensis Mann were foraging outside the nest with workers (
In the following, we will discuss this new finding in D. quadripunctatus in the light of the biology and life history of the species. It is a Euro-West-Siberian xerothermophilic oligotope of warm bright forests, also found in old orchards, gardens and parks. It is a dendrobiontic species which forages almost exclusively on trees (mainly in canopies) and is well adapted to move around the leaves (
The species avoids encounters with heterospecific ants (
It is noteworthy that
An evident first reason for the alate gyne(s) to leave the nest and follow worker trails to aphid colonies is an acute shortage of food in the nest. Indeed, in Poland the spring of 2017 was late and cool, and the summer generally rainy and unfavourable for insects, when alate gynes of D. quadripunctatus were observed at the aphids. The supposition that hunger drives alate gynes to forage is justified in light of the observation of
The impact of evident food shortage on the behaviour of ants, probably caused by an exceptionally dry summer, was reported by
To see how the foraging of alate gynes could contribute to the colony dynamics, an introduction to the social structure of a D. quadripunctatus colony is at place. Typically, it is monogynous polydomy with one main queenright nest and a few branch nests inhabited by workers with possible offspring. This structure is caused by the small size of individual nest spaces which most often can harbour maximally several tens of individuals; the entire colony usually consists of several hundred, rarely over 1000 adults (
Direct observations on how a gyne is able to find a queenless workforce and start a colony are lacking. It has been suggested that a group of workers may take the gyne to a queenless outpost nest (
If our above suggestion has any value in the colony dynamics of D. quadripunctatus, the question remains, why alate gynes seem to be only very occasional visitors at aphid colonies. One evident reason is that the yearly number of gynes produced by a colony is low (
We thank the editor Petr Klimeš and two reviewers, whose comments helped to improve the article.