Morphological Modification of the Mouthparts of Aphids (Hemiptera: Sternorryncha: Aphididae)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript by Shi et al. on the comparative morphology of the aphid labrum and labium is in excellent shape and a significant contribution to the science

 My most important observation is in the materials and methods. The authors should describe the basic biologies of the nine species, especially their host plants and feeding locations. It is also critical that there be a description of the methods and tools used to identify the specimens. Ideally, they would also to cite actual voucher specimens, presumably taken from the same colonies. Future readers need to know if the identifications can be trusted.

 I only have a few other corrections to suggest.

Line 24. In fact, there are nine species discussed, not eight. Also, it is important to mention that six subfamilies are represented.

Lines 29, 598, 611, etc. Here and throughout the manuscript, the authors refer to “trichodea 2”, “basiconic 2”, etc. This is a combination of a full name and an abbreviation. The authors should choose either to write out the full names of the sensilla, for example “sensilla trichodea type 2” and “sensilla basiconica type 1” or they should use the abbreviation, for example “st2” and “sb1”.

In the abstract, the names should be written out completely.

Lines 68, 903. See Hottes, F.C. (1954) Some observations on the rostrum of Cinara puerca Hottes (Aphidae). The Great Basin Naturalist, 14, 83–86. This article significantly predates Brozek et al.

Lines 76, 917, 919. “Labium” is singular, but the sentence is written as if it were plural. I suggest rephrasing the sentence to refer to the labium in the singular, but either way, the sentence should be reviewed.

Line 157. Extra space.

Line 180. It is only “exclusively” based on your observations. Rephrase this sentence.

Line 248. “sp.” not in italics.

Line 580. Mention that both species belong to the same subfamily (Lachninae).

Line 587. “Concentrated on the ventral, lateral, and dorsal surfaces.” What other surfaces are there? Maybe state that they can be concentrated on “all surfaces” or “any surface”?

Line 885. Extra space.

Line 897. Perhaps cite Chen et al. where they show that the Lachninae ancestral feeding location was on woody parts of the host. Chen, R., Favret, C., Jiang, L., Wang, Z. & Qiao, G. (2015) An aphid lineage maintains a bark-feeding niche while switching to and diversifying on conifers. Cladistics, 32(5), 555–572.

Line 914. The manuscript uses the subfamily classification system. As such, Pemphigidae should be listed as Pemphiginae.

Line 914. Extra space.

Line 923. I think this should be a fusion of III + IV, not IV + V

Line 924. “noted in other aphids” requires a citation.

Lines 936, 939, 990. Italicize generic and species names.

Line 962. Don’t use abbreviation when starting a sentence.

Line 967. “Sternorrhyncha of root-feeding” … [2; 8] ... correct.

Lines 990, 1006, 1010. Add authority names to species names at first mention.

Author Response

Thank you very much for your valuable comments and constructive feedback on our manuscript "Morphological modification of the mouthparts of aphids (Hemiptera: Sternorryncha: Aphididae)." We truly appreciate the time and effort you have dedicated to reviewing our work. We made our best effort to improve the manuscript and implemented changes according to the reviewers' suggestions. All the changes are marked in purple in the revised paper. We have clarified the methods, data presentation, and interpretation, making sure they align with the study’s objectives and findings.

Your thoughtful feedback has been invaluable in strengthening our manuscript, and we are confident that the revised version now meets the high standards required for publication in "Insect".

 

Responses to reviewer 1.

 

1. Comment 1# R1. My most important observation is in the materials and methods. The authors should describe the basic biologies of the nine species, especially their host plants and feeding locations. It is also critical that there be a description of the methods and tools used to identify the specimens. Ideally, they would also to cite actual voucher specimens, presumably taken from the same colonies. Future readers need to know if the identifications can be trusted.

Response 1. We modified the Materials and Methods and introduced two points. 2.2 and 2.3 in this section are connected with the description of the methods and tools used to identify the specimens,  basic biologies of species, and actual voucher specimens and the number of specimens used in this study.

 

2.2. Collection, voucher materials and descriptions of the specimens

In this study, eight morphs of apterous viviparous females were used, and only Panaphis juglandis was an alate viviparous female. All species determinations were performed following the key by Blackman and Eastop [23]. Collection of data of the studied specimens with accession numbers of the voucher material deposited in the entomological collection of the University of Silesia in Katowice (DZUS):

Uroleucon sp. coll. 20.06.2025. on Cichorium intybus, in Krośnice, Poland, leg. Ł. Depa; feeding on stems and bases of inflorescences; not visited by ants; det. Ł. Depa; apterous viviparous females; voucher material – microscopic slide no. DZUS 20.06.25.14-25.

Glyphina betulae coll. 20.06.2025. on Betula pendula, in Krośnice, Poland, leg. Ł. Depa; green tips of young branches with young leaves, not attended by ants. det. Ł. Depa; apterous viviparous females; voucher material – microscopic slide no. DZUS 20.06.25.15-25.

Myzus cerasi coll. 20.06.2025. on Prunus avium, in Krośnice, Poland, leg. Ł. Depa; in young, curled leaves, in very abundant colonies; not visited by ants; det. Ł. Depa; apterous viviparous females; voucher material – microscopic slide no. DZUS 20.06.25.16-25. 

Panaphis juglandis coll. 23.06.2025, on Juglans regia, in Krośnice, Poland, leg. Ł. Depa; on upper surface of leaves, along main veins; visited by Lasius niger; det. Ł. Depa; alate viviparous females; voucher material – microscopic slide no. DZUS 23.06.25.25-25.

Chaitophorus sp. coll. 23.06.2025, on Populus tremulae, in Krośnice, Poland, leg. Ł. Depa; on undersides of young leaves; visited by Formica cinerea; apterous viviparous females; voucher material – microscopic slide no. DZUS 23.06.25.31-25. 

Lachnus roboris coll. 26.06.2025, on Quercus robur, in Krośnice, Poland, leg. Ł. Depa; on 2-3 years old, woody branches; visited by Lasius niger; apterous viviparous females; voucher material – microscopic slide no. DZUS 26.06.25.38-25.  

Forda sp. coll. 02.08.2025, on Bromus carinatus, in Piekary Śląskie, Poland, leg. Ł. Depa; on roots; visited by Lasius niger; apterous viviparous females; voucher material – microscopic slide no. DZUS 2.08.25.72-25.     

Paracletus cimiciformis coll. 27.07.2025, on Poa compressa, in Rybnik, Poland, leg. Ł. Depa; few specimens were feeding on roots, but most were loosely walking in ant chambers among ant brood; in colony of Tetramorium cf. caespitum. apterous viviparous females; voucher material – microscopic slide no. DZUS 27.07.25.67-25.     

Trama sp. coll. 24.08.2025. on Artemisia campestris, in Kołobrzeg, Poland, leg. Ł. Depa; on roots and underground rhizomes; visited by Lasius niger; apterous viviparous females; voucher material – microscopic slide no. DZUS 24.08.25.90-25.

 

2. Comment # R1.

Line 24. In fact, there are nine species discussed, not eight. Also, it is important to mention that six subfamilies are represented.

Response 2, it was changed:

Comparative morphological analysis of the labrum and labium among nine aphid species—Uroleucon sp., Glyphina betulae, Myzus cerasi, Panaphis juglandis, Chaitophorus sp., Lachnus roboris, Forda sp., Paracletus cimiciformis, and Trama sp., belonging to six subfamilies—reveals marked interspecific variation in structure, segmentation, and sensilla equipment.

3. Comment # R1. Lines 29, 598, 611, etc. Here and throughout the manuscript, the authors refer to “trichodea 2”, “basiconic 2”, etc. This is a combination of a full name and an abbreviation. The authors should choose either to write out the full names of the sensilla, for example “sensilla trichodea type 2” and “sensilla basiconica type 1” or they should use the abbreviation, for example “st2” and “sb1”.

Response 3: After using the full terminology of the sensilla, in the next sentences, the abbreviation of the name sensilla was used throughout the manuscript.

"Sensilla trichodea (St1-St5) are widespread across taxa, showing the highest densities in Chaitophorus sp St1, Trama sp. and L. roboris St2, Uroleucon sp St3, P. cimiciformis St4, whereas Trama sp. uniquely combines sensilla St2, St3, St5 and sensilla basiconica (Sb2). Sensilla basiconica (Sb1) are consistently positioned at the base of the labrum and the fourth labial segment, except in Trama sp., which presents sensilla St3". 

4. Comment # R1. In the abstract, the names should be written out completely.

Response 4: In the abstract, the complete name was introduced.

Uroleucon sp., Glyphina betulae, Myzus cerasi, Panaphis juglandis, Chaitophorus sp., Lachnus roboris, Forda sp., Paracletus cimiciformis, and Trama sp.

5. Comment # R1. Lines 68, 903. See Hottes, F.C. (1954) Some observations on the rostrum of Cinara puerca Hottes (Aphidae). The Great Basin Naturalist, 14, 83–86. This article significantly predates Brozek et al.

Response 5: Cinara puerca Hottes, which also belongs to Lachninae was indicated to have long stylets and a long, five-segmented labium that is almost as long as the body. Like Stomaphis, Cinara telescopes the segments during feeding on pine bark [7].  7.  Hottes, F.C. Some observations on the rostrum of Cinara puerca Hottes (Aphidae). The Great Basin Naturalist, 1954, 14, 83–86.

6. Comment # R1. Lines 76, 917, 919. “Labium” is singular, but the sentence is written as if it were plural. I suggest rephrasing the sentence to refer to the labium in the singular, but either way, the sentence should be reviewed.

Response 6: These sentences are changed.

Line 76: By contrast, a leaf- or stem-feeding species such as Aphis fabae Scopoli or Myzus persicae (Sulzer) has a shorter, four-segmented labium that terminates near the hind coxa, but the length of the labium is sufficient for accessing phloem near the epidermal surface [3].

Lines 917-920: A shorter labium reduces the leverage force and facilitates shallow penetration, minimising mechanical stress on the slender stylets [3, 15]. Conversely, an elongated, five-segmented labium, characteristic of Lachnus, Stomaphis, and Trama, is found in a taxon that feeds on lignified or subcortical tissue. In this case, the rostrum must penetrate a substantial mechanical barrier and remain stable during prolonged ingestion.

7. Comment # R1. Line 157. Extra space.

Response 7: deleted

8. Comment # R1.Line 180. It is only “exclusively” based on your observations. Rephrase this sentence.

Response 8: The sentence is changed:

This sensillum type is presently observed in Trama sp.

9. Comment # R1. Line 248. “sp.” not in italics.

Response 9: It was changed.

10. Comment # R1. Line 580. Mention that both species belong to the same subfamily (Lachninae).

Response 10: It was changed.

Some studied species have a labium divided into four segments, although Trama sp. and L. roboris have five segments (both species belong to the Lachninae).

11. Comment # R1. Line 587. “Concentrated on the ventral, lateral, and dorsal surfaces.” What other surfaces are there? Maybe state that they can be concentrated on “all surfaces” or “any surface”?

Response 11: The sentences of lines 587-593 were changed:

Sensilla distribution:

• Across the examined aphid taxa, five types of sensilla trichodea (St1–St5) and five types of sensilla basiconica (Sb1–Sb5) are distinguished,varying in length (Table1). Sensilla trichodea represent the most abundant (Table 3) and widely distributed sensillum type, whereas sensilla basiconica show stronger positional and taxon-specific constraints.
• Sensilla (St1–St4) typically occur on the second to fourth labial segments. Sensilla St5 is restricted to the second segment in Trama, suggesting that this taxon has specific characters.
• Sensilla (Sb1-Sb5) show greater functional differentiation. Sensilla Sb1 is conserved across all examined taxa except for Trama and consistently occurs at the base of the labrum and the ventral base of the terminal labial segment, supporting its interpretation as a conserved proprioceptive/mechanosensory element. In contrast, Sb2–Sb3 exhibit restricted distributions to the apex of labium, but Sb4-Sb5 are associated in Forda sp. with all surfaces of the labium.

12. Comment # R1. Line 885. Extra space.

Response 12: Deleted

13. Comment # R1. Line 897. Perhaps cite Chen et al. where they show that the Lachninae ancestral feeding location was on woody parts of the host. Chen, R., Favret, C., Jiang, L., Wang, Z. & Qiao, G. (2015) An aphid lineage maintains a bark-feeding niche while switching to and diversifying on conifers. Cladistics, 32(5), 555–572.

Response 13: Some information has been added.

Lachninae represent an ancestral lineage that includes numerous woody-tissue phloem feeders. The genus Cinara dominates species diversity, feeding exclusively on woody tissues and comprising the largest extant radiation of aphids on conifer hosts. Lachnini are less species-rich but utilise a broader range of woody angiosperm hosts, whereas Tramini form a distinct lineage that feeds on the roots of herbaceous angiosperms.

[27].    Chen, R., Favret, C., Jiang, L., Wang, Z., Qiao, G. An aphid lineage maintains a bark-feeding niche while switching to and diversifying on conifers. Cladistics, 2016, 32, 555-572. http://dx.doi.org/10.1111/cla.12141.

14. Comment # R1. Line 914. The manuscript uses the subfamily classification system. As such, Pemphigidae should be listed as Pemphiginae.

Response 14: It was changed on Pemphiginae.

15. Comment # R1. Line 914. Extra space.

Response 15: Deleted

16. Comment # R1. Line 923. I think this should be a fusion of III + IV, not IV + V

Response 16:  This part was changed.

Occasional reductions to three apparent segments, as reported for Aphis citricola van der Goot (Aphidinae: Aphidini) [33], probably result from the fusion of some segments. A phenomenon of three-segmented labium was also indicated in another aphid, e.g. Euthoracaphis umbellulariae (Essig) (Hormaphidinae: Nipponaphidini), which lives and feeds on the leaf undersides of plants of the Lauraceae [34].

17. Comment # R1. Line 924. “noted in other aphids” requires a citation.

Response 17: The citation is added, and the sentences are modified.

Occasional reductions to three apparent segments, as reported for Aphis citricola van der Goot (Aphidinae: Aphidini) [33], probably result from the fusion of some segments. A phenomenon of three three-segmented labium was also indicated in another aphid, e.g. Euthoracaphis umbellulariae (Essig) (Hormaphidinae: Nipponaphidini), which lives and feeds on the leaf undersides of plants of the Lauraceae [34].

18. Comment # R1. Lines 936, 939, 990. Italicize generic and species names.

Response 18: corrected to italics

19. Comment # R1. Line 962. Don’t use abbreviation when starting a sentence.

Response 19: It was changed:

Feeding on grass roots, P. cimiciformis also exhibits a polygonal, granular surface pattern, possibly linked to enhanced tensile resilience, particularly during subterranean interactions or ant-associated life stages.

20. Comment # R1. Line 967. “Sternorrhyncha of root-feeding” … [2; 8] ... correct.

Response 20: The sentence was deleted because the cuticular processes (Cup) were not sufficiently described by the cited authors; we inferred these structures only from the image.

21. Comment # R1. Lines 990, 1006, 1010. Add authority names to species names at first mention.

Response 21: Authority names were added.

Oncopeltus fasciatus (Dallas), Bemisia tabaci Gennadius, Cacopsylla chinensis 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

“Morphological modification of the mouthparts of aphids (Hemiptera: Sternorryncha: Aphididae)”

 

This manuscript documents the morphology of the highly modified mouthparts in eight species of aphids / Aphididae. The authors use scanning electron microscopy and measurement of structural dimensions to compare the rostrum (labium) and labrum for their proportions, as well as identification of cuticular sensilla structures to identify anatomical and sensory adaptations to different host plants.

While the stylet and rostrum of aphids has been studied for the sucking gain of phloem sap from host plants, the specific adaptations to different host plants are further investigated here, including the sensory elements involved in this use of plants. The approach is very important for ecological adaptations, evolutionary diversity, and sensory ecology of insects. The results are documented in detail and the figures are of the very good quality. The authors discuss their results for different aspects of functional morphology, sensilla diversity, mechanosensory functions, and the ecological and evolutionary context. The results contribute important insights from a comparative and ecological framework to the functional morphology of aphids. While the manuscript is very dense in information, the authors present the details resulting from sem and measurements in the text for individual species, and for comparison in tables and figures. The manuscript requires some editing in the presentation of certain aspects:

 

For general orientation, consider to include a further sem image or a schematic of the entire aphid head and mouthparts – this would help the orientation for details and axes from specific mouthparts shown in the following figures. 

 

            The authors compile in their study their current data and published data (l. 126) and review available data (l. 863). This is not fully clear if the work present original data, or if the data have been published previously? The presentation of results appears to be a novel study. Further, instead of addressing “preliminary morphological diversity” (l. 128), the introduction could present a hypothesis on diversity and its adaptive relevance in aphids for (a) rostrum structure and (b) related differences in sensilla. This would also aid the discussion for the ecological context.

 

            Was the sample size one individual from each species (see l. 135 / 137)? What was the sex of these individuals? Did you find possible indications for sexual dimorphism, as it was shown in some cases for apical labial sensilla in Acyrthosiphon pisum (Kanturski et al. 2020 Europ Zool J)?

 

            For length measurements, how were the specimen or sensilla aligned for micrographs to present identical axes of different hairs?

 

l. 91 "mechanical properties" – do you mean morphological properties, since not much is known about the mechanical properties of individual hairs ?

l. 94 Listing of references: delete “and”?

l. 99 The references cited here validating the comparison address only two species (rather than “most aphids”)

l. 249, 254 Reading of the morphological shapes and values of length and width together with the different anatomical details and sensilla is quite dense. Since all of the measurements are summarised and compared in Tables 2 and 3, they should be at least referred to in the text.

l. 213 is there a reference for the sensilla schematics?

l. 260 specify: Figures 1C and 7A

l. 366 …ventrally, two pairs…

l. 531 … though two species, Trama sp. and Forda sp., have a conical labrum.

l. 536 The remaining species / The other species…

l. 574 The lower section of Fig. 6 is not included

l. 615 instead of naming some examples for the most common sensilla pattern at the tip, name the two species here that differ by having 7 pairs of sensilla basiconica 2 in Lachnus roboris and Trama.

l. 620 Sensilla trichodea 5 are notably found only in Trama sp. and L. roboris, with more sensilla present in Trama sp.

l. 623 …with only few to none of the other types of sensilla present in the second segment. – Additionally, name the species here regarding the specific distributions (little – none)?

l. 628 …have a notably larger labium with more complex sensory structures?

l. 630 P. juglandis also shows dense sensilla on segment II of the labium?

l. 657 Scales refer to Figures E – I, but these elements are not present in the panel

l. 950 The apical field is certainly conserved while the number and types of sensilla basiconica differ in Lachnus and Trama with a unique arrangement of 7 pairs of sb2. This pattern of 7 pairs of sensilla basiconica was also documented in Pseudessigella brachychaeta (Kanturski et al. 2017, Zool Anz 266: 1), could you include this for some more general statement on the adaptations of s. basiconica at the labial tip?

l. 996 Wensler 1977 also identifies the tubular body in the sensilla in Brevicoryne brassicae

l. 1002 add: …a tubular body, which is indicating a mechanosensory role…

l. 1017 Are these sensilla also s. trichodea?

l. 1022 Can you make a short relation to the role of chemosensation, are chemosensilla located on the stylet?

Author Response

Thank you very much for your valuable comments and constructive feedback on our manuscript "Morphological modification of the mouthparts of aphids (Hemiptera: Sternorryncha: Aphididae)." We truly appreciate the time and effort you have dedicated to reviewing our work. We made our best effort to improve the manuscript and implemented changes according to the reviewers' suggestions. All the changes are marked in purple in the revised paper. We have clarified the methods, data presentation, and interpretation, making sure they align with the study’s objectives and findings.

Your thoughtful feedback has been invaluable in strengthening our manuscript, and we are confident that the revised version now meets the high standards required for publication in "Insect".

 

Responses to reviewer 2.

1. Comment # R2. For general orientation, consider to include a further sem image or a schematic of the entire aphid head and mouthparts – this would help the orientation for details and axes from specific mouthparts shown in the following figures.

Response1. The aphid with the head and rostrum is added.

Figure 2. Ventral view of Chaitophorus sp. showing the mouthparts extended from between the forecoxae (Fc). Abbreviations: Ⅱ–Ⅳ, different labium segments; Ac, ante-clypeus; Lm, laburm; Lb, Labium; Sf, stylet fascicle. Bars = 200μm.

2. Comment # R2

            The authors compile in their study their current data and published data (l. 126) and review available data (l. 863). This is not fully clear if the work present original data, or if the data have been published previously? The presentation of results appears to be a novel study. Further, instead of addressing “preliminary morphological diversity” (l. 128), the introduction could present a hypothesis on diversity and its adaptive relevance in aphids for (a) rostrum structure and (b) related differences in sensilla. This would also aid the discussion for the ecological context.

Response 2. The aim of the study is modified.

This study presents our original quantitative and qualitative data on rostrum structure, sensilla morphology and distribution in representative Aphididae taxa. We test the hypothesis that the diversification of rostrum and sensilla traits in aphids is associated with host-plant niche differentiation (leaf, stem, trunk or root feeding), and we discuss the evolutionary trends underlying these adaptations.

3. Comment # R2 Was the sample size one individual from each species (see l. 135 / 137)? What was the sex of these individuals? Did you find possible indications for sexual dimorphism, as it was shown in some cases for apical labial sensilla in Acyrthosiphon pisum (Kanturski et al. 2020 Europ Zool J)?

Response 3. The additional information is added to the Materials and Methods, in point 2.2. 2.3.

Five specimens of each species were selected for the recognition of particular types of sensilla. Sample size: Eight sensilla were measured from each specimen for sensilla types St1-4 and Sb2–3. Five sensilla were measured for sensilla of particular types, St5, Sb1, and Sb4–5; in Trama sp., five sensilla were measured for sensilla type St3.

 In this study, eight morphs of apterous viviparous females were used, and only Panaphis juglandis was an alate viviparous female. All species determinations were performed following key by Blackman and Eastop [23]. Collection of data of the studied specimens with accession numbers of the voucher material deposited in the entomological collection of the University of Silesia in Katowice (DZUS):

In this study, we had only females.

4. Comment # R2

            For length measurements, how were the specimen or sensilla aligned for micrographs to present identical axes of different hairs?

Response 4.

The position for measuring the sensilla on the surface labrum and labium, and apex of the labium was selected in the same way for all specimens, with the sensilla visible laterally to the surface (see Figure 1). The labium was positioned as parallel as possible to the field of view, and sensilla were found in a natural position, not destabilised by being electron in a scanning electron microscope. The lateral position of the sensilla shows their true length from the socket to the distal end. Also, we added a new Figure 1. The positions for measuring the sensilla on the surface of the labium. (A) Example of the selection and measurement of the length of sensilla trichodea St1. (B) An example of the selection and measurement of the length of sensilla trichodea St3. Bars = 30 µm. Abbreviation: lg, labial groove.

5. Comment # R2. l. 91 "mechanical properties" – do you mean morphological properties, since not much is known about the mechanical properties of individual hairs ?

Response 5. The sentence is changed to:

Many insects have diverse sensilla on their labrum and labium that have evolved to have highly specialised morphology (stiff wall of hair and flexible socket), pointing to touch mechanical properties in accordance with their ecological requirements [9].

6. Comment # R2 l. 94 Listing of references: delete “and”?

Response 6. deleted

7. Comment # R2 l. 99 The references cited here validating the comparison address only two species (rather than “most aphids”)

Response 7. It has been shown in aphids that mechano-trichoid sensilla are primarily concentrated on the final labial segment, where they are likely to monitor stylet insertion, position, and tissue resistance [16, 17]

8. Comment # R2 l. 249, 254 Reading of the morphological shapes and values of length and width together with the different anatomical details and sensilla is quite dense. Since all of the measurements are summarised and compared in Tables 2 and 3, they should be at least referred to in the text.

Response 8. Reference to tabular data is more often cited, especially when analysing traits in individual species.

9. Comment # R2. l. 213, is there a reference for the sensilla schematics?

Response 9. The sensilla schematic was prepared based on our current SEM images. After the correction, the schema is numbered as Figure 3, and cited in the text, section 3.1.1.

10. Comment # R2. l. 260 specify: Figures 1C and 7A

Response 10. This sentence now sounds:

This segment has numerous sensilla (St3), at least a dozen pairs, primarily distributed along both sides of the labial groove and the lateral surfaces (Figures 9A, 11A).

11. Comment # R2. l. 366 …ventrally, two pairs…

Response 11. The verse is modified in detail.

The fourth segment is approximately 196.7 μm long and conical in shape, without distinct constriction or tapering at the tip. It has seven to eight pairs of sensilla St1, distributed as follows: four pairs along both sides of the labial groove (nos.. 1-4) (Figure 10A), one pair laterally (no 2), and three pairs dorsally (nos.. 1-3) (Figure 12B).

12. Comment # R2. l. 531 … though two species, Trama sp. and Forda sp., have a conical labrum.

Response 12. The sentence is modified.

The labrum is triangular and plane-like in most species, except for Trama sp. and Forda sp., which have a labrum more convex on the dorsal side, "conical-shaped".

13. Comment # R2. l. 536 The remaining species / The other species…

Response 13. We changed on: The other species Uroleucon sp., G. betulae, M. cerasi, P. juglandis, Chaitophorus sp., L. roboris, P. cimiciformis) show no sensilla on the labrum surface, although all have a pair of sensilla basiconica (Sb1) at the base of the labrum, closely adjoined to the lateral sides.

14. Comment # R2. l. 574 The lower section of Fig. 6 is not included

Response 14. Sorry, during the creation of the PDF, this figure has been shortened.

15. Comment # R2. l. 615 instead of naming some examples for the most common sensilla pattern at the tip, name the two species here that differ by having 7 pairs of sensilla basiconica 2 in Lachnus roboris and Trama.
16. Comment # R2. l. 620 Sensilla trichodea 5 are notably found only in Trama sp. and L. roboris, with more sensilla present in Trama sp.
17. Comment # R2. l. 623 …with only few to none of the other types of sensilla present in the second segment. – Additionally, name the species here regarding the specific distributions (little – none)?
18. Comment # R2. l. 628 …have a notably larger labium with more complex sensory structures?
19. Comment # R2 l. 630 P. juglandis also shows dense sensilla on segment II of the labium?

Response 15-19 to the comments together.

To avoid repetition when listing species and their characteristics, the section 3.2.2. Labium comparison has been improved (Sensilla distribution, Special features, Conical and tapering segments; Sensilla types and distribution patterns, Overall summary of comparison). Below improvement part.

3.2.2. Labium comparison

Segment Number and Length: Some studied species have a labium divided into four segments, although Trama sp. and L. roboris have five segments (both species belong to the Lachninae). The second segment is generally the longest across species, though its length varies significantly. For example: Uroleucon sp. 441.0 μm, L. roboris: 883.9 μm, Trama sp.: 572.1 μm (Table 3). The first segment is a membranous, sleeve-like structure in all species, with no sensilla, serving to partially envelop the second segment. Leaf- and shoot-feeding species (Uroleucon sp., M. cerasi, P. juglandis, Chaitophorus sp.) possess relatively short labium (≈500–900 µm). These labia show moderate sensilla densities, reflecting reduced mechanical demands when accessing superficial phloem. In turn twig- and bark-feeding species (L. roboris) exhibit extremely elongated labia (>1400 µm), including a highly extensible first segment and densely sensillated second and third segments. This morphology facilitates penetration through lignified tissues and prolonged feeding. However, root feeder species (Forda sp., P. cimiciformis, Trama sp.) display intermediate to long labia (700-1300 µm) with pronounced sensilla specialisation (Sb4, Sb5, St5).

Sensilla distribution:

• Across the examined aphid taxa, five types of sensilla trichodea (St1–St5) and five types of sensilla basiconica (Sb1–Sb5) are distinguished,varying in length (Table1). Sensilla trichodea represent the most abundant (Table 3) and widely distributed sensillum type, whereas sensilla basiconica show stronger positional and taxon-specific constraints.
• Sensilla (St1–St4) typically occur on the second to fourth labial segments. Sensilla St5 is restricted to the second segment in Trama, suggesting that this taxon has specific characters.
• Sensilla (Sb1-Sb5) show greater functional differentiation. Sensilla Sb1 is conserved across all examined taxa except for Trama and consistently occurs at the base of the labrum and the ventral base of the terminal labial segment, supporting its interpretation as a conserved proprioceptive/mechanosensory element. In contrast, Sb2–Sb3 exhibit restricted distributions to the apex of labium, but Sb4-Sb5 are associated in Forda sp. with all surfaces of the labium.
• Special features: Trama sp. features cuticular processes (Cup) at the apex of the labium, which are also seen in L. roboris. Morover, the last has distinct granular cuticular protrusions on the lateral and dorsal surfaces of the second segment, forming honeycomb-like patterns that are absent in other species.
• Conical and tapering segments: The fourth segment tends to taper toward the apex and is often conical in shape for most species. This is especially true for M. cerasi, P. juglandis, Trama sp., Forda sp., P. cimiciformis and L. roboris, while Uroleucon sp. and G. betulae show more smooth or less distinct tapering.

 

Sensilla types and distribution patterns (Table 3)

• Sensilla basiconica: A pair of sensilla (Sb1) is located at the ventral base of the fourth segment of the labium in most species. Eight pairs of sensilla (Sb3) are found at the tip of the labium in the studied species except Trama and L. roboris, which possess seven pairs of sensilla (Sb2). In Forda sp. –labial surface is covered by the sensilla basiconica Sb4 and Sb5and only a few sensilla St3 are observed on the last segment. .
• Sensilla trichodea: Sensilla (St1), (St2) and (St3) are common in certain species, but St1 is generally found in higher numbers than St3, particularly on the ventral and lateral surfaces of juglandis and Chaitophorus sp. The common type of St2 sensillum was found in L. roboris and Trama sp., whereas Uroleucon sp., G. betulae and M. cerasi mainly exhibit St3 sensilla from the second to fourth segments. Trichodea sensilla St4 are notably found in P. cimiiformis, whereas St5 are restricted to Trama sp.

Special variations: In Uroleucon sp., M. cerasi and G. betulae, sensilla St3 are highly concentrated in specific regions such as the ventral labial groove and lateral surfaces, with no other types of sensilla trichodea in the segments. L. roboris and Trama sp. stand out for the sheer number of sensilla trichodea 2 found on the segments, distributed symmetrically on all surfaces. Sensilla trichoidea St3 have been observed at the ventral base of the fourth segment in the Trama sp.

Overall summary of comparison:

• Size Variations: Five-segmented labia occur in roboris, and Trama sp., while the remaining species possess four-segmented labium.
• Sensilla Patterns: Trama sp. is unique for its combination of sensilla (St2, St3 and St5) and sensilla (Sb2), along with the highest concentration of sensilla (St2) on its second and third segments.
• Unique Features: Only Trama sp. and roboris contains a combination of cuticular processes and distinct granular protrusions, which sets it apart from the other aphids that mostly share basic sensory structures on the labium, particularly on the second segment.

20. Comment # R2. l. 657 Scales refer to Figures E – I, but these elements are not present in the panel.

Response 20. Sorry, the mistake has been moved from the work version. Correctly is: Bars in Figure A = 200 μm, B-D = 100 μm.

21. Comment # R2 l. 950 The apical field is certainly conserved while the number and types of sensilla basiconica differ in Lachnus and Trama with a unique arrangement of 7 pairs of sb2. This pattern of 7 pairs of sensilla basiconica was also documented in Pseudessigella brachychaeta (Kanturski et al. 2017, Zool Anz 266: 1), could you include this for some more general statement on the adaptations of s. basiconica at the labial tip?

Response 21. The part is modified.

The apical sensory field, formed by concentric rings of eight pairs of sensilla (Sb3) of varying length from 3,5-6,8 μm, was observed across seven studied species. Another pattern was observed, with seven pairs of Sb2. Their lengths range from 11.1 μm in Trama sp. to 16.5 μm in L. roboris. Similar to Cinara pilicornis (Hartig), the apical end of the last rostral segment has seven pairs of (5.50–6.50 μm) in length, smooth sensilla basiconica (type III) [37]. Although Trama sp., L. roboris, and C. pilicornis represent a common subfamily (Lachninae), the last species was found to have other types of sensilla, but in the same number. The pattern of seven pairs of sensilla basiconica (Sb3) has also been documented in Pseudessigella brachychaeta Hille Ris Lambers (Lachninae) [38], and this feature has also been seen in Eriosoma lanigerum (Eriosomatinae) (Hausmann) [32]. The pattern with the seven Sb3 is shared by species from different subfamilies, including Lachninae and Eriosomatinae, indicating that this trait is not strictly subfamily-specific. Although variation exists in sensillum length and type among species such as Trama sp., L. roboris, and C. pilicornis, the conserved number and arrangement suggest a common functional role.

22. Comment # R2l. 996 Wensler 1977 also identifies the tubular body in the sensilla in Brevicoryne brassicae

Response 22. This information in this sentence is added: Each peg is innervated by a single sensory neuron that is anchored eccentrically to a basal cuticular tube and terminates in an electron-dense material dendritic sheath with densely grouped microtubules that form a tubular body at the base of the peg.

23. Comment # R2l. 1002 add: …a tubular body, which is indicating a mechanosensory role…

Response 23: The sentence is changed:

Similar findings were reported by Tjallingii [16], who confirmed that in B. brassicae, both the tip sensilla and the sensilla (larger labial hairs) located in more proximal regions are innervated by a single dendrite with a tubular body, which indicates a mechanosensory role.

24. Comment # R2l. 1017 Are these sensilla also s. trichodea?

Response 24. This information in this sentence is added:

The present study showed a high density of sensilla (St2) on the second and third segments in Trama sp. and L. roboris. These sensilla probably facilitate fine-scale control of labial curvature and penetration depth, similar to the other type of sensilla (St1- St5) in other species. Moreover, proprioceptive sensilla (St3- in Trama, and in other species Sb1) are also present on the borders of the segments. These structures are likely homologous to the proprioceptive basiconic sensilla (Sb) or trichoid (St) observed in other hemipterans, which detect segmental deformation or curvatures [15,16].

25. Comment # R2l. 1022 Can you make a short relation to the role of chemosensation, are chemosensilla located on the stylet?

Response 25.

The rostrum of aphids is complemented by a second, sensory system associated with the mandibular stylets. Classic morphological studies have demonstrated that only the mandibular stylets are innervated, whereas the maxillary stylets lack neural elements. Forbes[17,49] reported nerve elements in the mandibular stylets of Myzus persicae and later provided a detailed account of stylet morphology and penetration mechanisms. These studies showed that only mandibular stylets contain paired dendrites with microtubule bundles. Similar observations were subsequently reported in Rhopalosiphum maidis (Fitch) (two axons and sensory dendrites within the central canal of each mandibular stylet), supporting the generality of innervation [50].

The innervation of mandibular stylets is consistent with a mechanosensory function. The paired dendrites likely detect mechanical resistance, tissue density, and stylet position during penetration and pathway selection through plant tissues. Mandibular receptors, as described in ultrastructural studies, are interpreted as mechanoreceptors involved in monitoring stylet movement and deformation at the labial tip. The presence of rigid receptor components, such as scolopales, further supports a role in detecting strain rather than chemical cues [17, 47]. Although two dendrites per mandibular stylet appear to be the most common condition, variation exists. Forbes and Mullick [51] reported three dendrites in the mandibular canal of Adelges piceae (Ratzeburg) (Adelgidae), suggesting evolutionary plasticity in sensory capacity that may reflect differences in feeding substrate or penetration depth.

Together, these studies support a dual sensory system in aphids, integrating external mechanosensory input from distal labial sensilla with internal feedback from innervated mandibular stylets. This system is crucial for various types of penetrating feeding in aphids, where precise control of labial and mandibular movement is essential for successful feeding and mechanical integrity during movement of the maxillae.

Author Response File: Author Response.pdf