Corresponding author: Grzegorz K. Wagner (
Academic editor: J. Klimaszewski
The paper describes the external structures of the late larval stages of two Palearctic myrmecophilous staphylinids:
Staniec B, Zagaja M, Pietrykowska-Tudruj E, Wagner GK (2018) Comparative larval ultramorphology of some myrmecophilous Aleocharinae (Coleoptera, Staphylinidae), with a first description of the larvae of
Red wood ants from the
Among the insects associated with ants, beetles (
The genus
The genus
Myrmecophilous
Presumably, the larval structure of these myrmecophiles, among other characteristics, which actively live and forage in the anthill throughout their development, should well reflect the extent and nature of their integration with their hosts. Therefore, detailed morphological data of the larval forms should prove useful for discovering the distinctive adaptations of myrmecophilous species to life in ant nests and also the relations between them and their hosts.
The links of numerous
It is apposite, therefore, to pose the following questions: 1) Does the myrmecophily of
The chief aim of this paper is therefore to describe in detail the morphology, including the chaetotaxies and external ultrastructure, of the larval stages of
Larval stages were obtained by rearing 34 adults of
Larvae of both species were killed in boiling water and preserved in ethanol (75%).
To prepare temporary microscope slides, some larvae were macerated in cold 10% KOH for two to three hours, immersed in lactic acid for subsequent preparation and mounting of antennae, mouthparts, sensory structures, chaetotaxy of the body, legs and urogomphi. They were then traced from photos taken with an Olympus DP72 or Olympus DP21 digital camera mounted on a binocular Olympus SZX16 or Olympus BX63 compound microscope (Figs
Habitus illustrations of larvae, structure of setae, chaetotaxy of head, functional position of mouthparts, structural details of antennae, microstructure, spiracles and various details of their external structure were recorded using SEM, type VEGA3 TESCAN (Figs
Measurements of the larvae of both species, made using an Olympus BX63 compound microscope in cellSens Dimension v1.9 software, are given in millimetres, as explained in detail in
Measurements of larval instars of
Species (larval instars/N) | M | R | A | SV |
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Body length | 1.00–2.55 | 1.99 | 0.45 | |
Thorax length | 0.38–0.69 | 0.55 | 0.09 | |
Head width | 0.16–0.23 | 0.20 | 0.02 | |
Prothorax length | 0.15–0.30 | 0.21 | 0.40 | |
Prothorax width | 0.18–0.27 | 0.23 | 0.03 | |
Body length | 2.46–3.32 | 2.79 | 0.37 | |
Thorax length | 0.40–0.80 | 0.68 | 0.09 | |
Head width | 0.22–0.27 | 0.25 | 0.02 | |
Prothorax length | 0.19–0.33 | 0.27 | 0.03 | |
Prothorax width | 0.23–0.32 | 0.28 | 0.02 |
The combination of characteristics distinguishing mature larvae of
Body narrow, elongate, semi-cylindrical, segments IX and X distinctly narrower than the others;
Pro- (Prs), meso- (Mes) and metasternum (Met) membranous (Figs
Table
This paper gives a detailed description of the external structure of the hitherto unknown larval stage of
Relationships between myrmecophiles and their hosts exhibit varying degrees of advancement (
Similarities and differences in external morphology between known late larval instars of some myrmecophilous and non-myrmecophilous
Ecological preferences | Myrmecophilous species | Non-myrmecophilous species | ||||
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Host |
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Tribe of |
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Species |
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level of integration with host | preadaptation to integration | peak of integration (symphile) | preadaptation to integration | non-integrated? (synoics) | – | |
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Body length | 4.30–4.80 | 4.99–6.70 | 2.72–4.40 | 2.46–3.32* | 1.00–2.55* | 3.01–3.78 |
Body shape | moderately elongate | dumpy | elongate | elongate | elongate | elongate |
Cuticle | mod. sclerotized | membranous | mod. sclerotized | poor. sclerotized | poor. sclerotized | mod. sclerotized |
Setae: structure | setose | blunt, jagged distally | setose | setose | setose | setose |
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Width | 0.57–0.63 | 0.87–0.97 | 0.41–0.48 | 0.22–0.27* | 0.16–0.23* | 0.42–0.45 |
LWr | 1:1 | 1:1.4 | 1:1 | 1.1:1 | 1:1.2 | 1:1 |
Ocelli | present | absent | present | present | present | present |
Ns: dorsal side | 40 | 70 | 42 | 40 | 40 | 40 |
Sides | distinctly rounded | distinctly rounded | distinctly rounded | weakly rounded | distinctly rounded | distinctly rounded |
Wr of head and Pnt | 1:1.3 | 1:1.5 | 1:1.3 | 1:1.1 | 1.1:1 | 1:1.1 |
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Lr of AI-III | 1.4:2.3:1 | 1.2:1.7:1 | 1.5:1.9:1 | 1.3 : 1.6 : 1 | 1.3:1.9:1 | 1:1.7:1 |
LWr of AI, AII, AIII | 1.2:1/2.4:1/2.2:1 | 1:2.8/1:1.1/1:1.6 | 1.2:1/1.4:1/2:1 | 1:1.2/1.5:1/1.6:1 | 1:1/1.5:1/1.5:1 | 1:1/1.8:1/1.4:1 |
LWr of Sa | 1.5:1 | 1.4:1 | 2.1:1 | 1.9:1 | 1.6:1 | 1.8:1 |
Lr Sa and AIII | 1:1.6 | 1.1:1 | 1:1.1 | 1:1.3 | 1.1:1 | 1:1 |
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Shape | trapeziform | trapeziform | semi-circular | semi-circular | rectangular | trapeziform |
Anterior margin | almost straight | slightly rounded | distinctly rounded | distinctly rounded | excised in the centre | cent. reg. protruding, crenate |
Seta Ld2: structure | mic. setose | macro, setose | macro, peg shaped | mic. verrucous | mic. spiniform | mic. spiniform |
Labium and clypeus | separated | fused | separated | separated | separated | separated |
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Cuticular processes: No. | well above 200 | well above 200 | 150–200 | 100–150 | about 20 | 50–80 |
Cut. proc.: length | short | short | short | short | long | short |
Cut. proc. in central area | absent | present | absent | absent | absent | present |
No. of pores of a/c/p | 2/8 (in 1 row)/ 4 | ? | 1–2/9/4 | 2/6 (in 2 rows)/2 | 0/2/0 | 2/4/4 |
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Shape | slender, bent weakly | slender, strong, bent | slender, weak, bent | slender, strong, bent | stocky, mod., bent | slender, weak, bent |
Interior edge ap. tooth | slightly undulating | smooth | smooth | serrate | smooth | smooth |
Edge below preap. tooth | slightly undulating | smooth | smooth | serrate | smooth | serrate |
No. of preap. teeth | 1-R and 1-L | 0 | 1-R and1-L | R-1 and L-1 | R-2 and L-2 | 4-R, 5-L |
Number/length of setae | 2/almost equal | 3/almost equal | 2/almost equal | 2/different | 2/almost equal | 2/equal |
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Mala: ant. marg. with: | 27–31 equal teeth | 8 equal setae | 20 teeth (11 small) | 11 teeth (1 big) | 12 teeth (4 small) | 23 teeth (15 small) |
Mala: shape | wide, equilateral, sclerotized | lobar, membranous | slender, slightly dilated anteriorly | slender, slightly narrowed anteriorly | wide, distinctly dilated anteriorly | slender, distinctly dilated anteriorly |
Ma: No. cut. proc./arrg. | about 80/singly | numerous/in rows | 55–60/singly | 15/singly | 25/ singly | 40/singly |
Stipes and mala | fused | separated | separated | fused | fused | separated |
Pm: Lr A I-III | 1.7:1:2.3 | 1.4:1:2.0 | 1.6:1:2 | 1.5:1.0:2.0 | 1.1:1.0:2.0 | 1.6:1:2.2 |
Pm: LWr of AI-III | 2.2:1/1.4:1/5.2:1 | 1:1.8/1:1.9/2.4:1 | 1.5:1/1.3:1/4.7:1 | 1.4:1/1.3:1/3.8:1 | 1.3:1/1.5:1/5.2:1 | 1.8:1/1.5:1/6.8:1 |
Lr: Pm and Ma | 1.5:1 | 1:1.2 | 1.1:1 | 1.1:1 | 1.2:1 | 1.2:1 |
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Lg: shape | transverse, short, | transverse, very short | finger-like, 1.8 × as long as wide | finger-like, 1.9 × as long as wide | domelike, as long as wide | finger-like, 2.5 × as long as wide |
Lg/anterior margin | sinuate | rounded | truncated | truncated | truncated | truncated |
Lr: Lg and Lp | 1:2.2 | 1:3.9 | 1:1.9 | 1:2 | 1:1.5 | 1:1 |
Lg and Pmnt | fused | fused | separated | fused | separated | separated |
Pl: Lr A I and II | 1:1.3 | 1:1 | 1:1.6 | 1:2.1 | 1:2.4 | 1:2.1 |
Pl: LWr of AI/AII | 1.1:1/2.4:1 | 1:1/1.6:1 | 2:1/3.2:1 | 1:1/3.1:1 | 1:1.4/2.9:1 | 1.1:1/3.5:1 |
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Ns: Pnt, Msn | 52, 40 | 110, 80 | 52, 38 | 50. 36 | 50, 36 | 50, 38 |
Lr: |
2.3:2.2:1 | 2.2:1.9:1 | 2.1:2.2:1 | 2.4:2.0:1.0 | 1.8:1.7:1.0 | 1.9:2.2:1 |
LWr: |
4.4:1/4.5:1/5.2:1 | 2.2:1/2.3:1/3.0:1 | 3.6:1/5.2:1/5.2:1 | 2.9:1/ 3.0:1/3.5:1 | 2..6:1/4.3:1/5.6:1 | 3.0:1/5.3:1/7.1:1 |
Ns: |
8, 9, 2 | 30–34, 22–25, 2 | 8, 9, 2 | 8, 9, 2 | 8, 9, 2 | 7, 9,2 |
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Ns: Tergite I, II-VII | 30, 30 each | 70, 80 each | 30, 32 each | 28, 32 | 28, 32 | 32 each |
Ns: St. I, each II-VIII | 16, 20 | 100, 110 | 14, 20 each | 16, 20 | 16, 20 | 16, 20 each |
Urogomphi | present | absent | present | present | present | present |
Ug: Lr AI, AII, Sap | 1:1.1:1.2 | – | 1:2.2:2.6 | 2.4:1.0:4.8 | 1.4:1.0:3.1 | 1:1.5:1.7 |
LWr AII | 2.7:1 | – | 3.7:1 | 2.5:1 | 2.8:1 | 4.1:1 |
Lr Ug (w. As) to S X | 1:1.7 | – | 1:1 | 1:1.4 | 1:1.5 | 1:1.5 |
By far the largest number of characteristic features of the external structure, compared with other myrmecophilous and non-myrmecophilous aleocharines, were found in the larva of the symphilous genus
The classification of the degree of integration of the other four myrmecophilous species of
In view of the above it cannot be surprising that, with the exception of
Therefore, as studies to date have shown, the characteristic morphology of the aleocharine larvae examined to date is not due to their myrmecophily alone. Likewise, the larval stages of myrmecophiles, which exhibit behavioural pre-adaptations to integration with host ants (
This analysis of the comparative morphology of known myrmecophilous aleocharine larvae in the context of the type of interaction with hosts is merely a preamble to far more extensive research on this subject. Unfortunately, as knowledge of the larval stage, not only of myrmecophilous but of other members of this very numerous staphylinid subfamily, remains fragmentary, the formulation of more comprehensive generalizations is as yet not possible. Moreover, there is still no information whatsoever on the detailed external larval structure of a number of other interesting, symbiotic European aleocharines. This situation can be illustrated by the genus
The authors gratefully acknowledge the State Forests National Forest Holding, Poland, for funding the research and the Management of the Polesie National Park for its cooperation. The project was carried out with the cooperation of the Polesie National Park and the Maria Curie-Skłodowska University in Lublin; the numbers of the relevant agreements are: EZ.0290.1.28.2017 (between PNP and SFNFH); 6, NB 520-3/2017 (between PNP and MCSU).