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Adaptive change in protective coloration in adultstriated shieldbugs Graphosoma lineatum (Heteroptera:Pentatomidae): test of detectability of two colour formsby avian predators
Stockholm University, Faculty of Science, Department of Zoology.
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2010 (English)In: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 35, no 5, 602-610 p.Article in journal (Refereed) Published
Abstract [en]

1. Protective coloration in insects may be aposematic or cryptic, and some species change defensive strategy between instars. In Sweden, the adult striated shieldbugs Graphosoma lineatum (Heteroptera: Pentatomidae) undergo a seasonal colour change from pale brown and black striation in the pre-hibernating adults, to red and black striation in the same post-hibernating individuals. To the human eye the pre-hibernating adults appear cryptic against the withered late summer vegetation, whereas the red and black post-hibernating adults appear aposematic. This suggests a possibility of a functional colour change. However, what is cryptic to the human eye is not necessarily cryptic to a potential predator.

2. Therefore we tested the effect of coloration in adult G. lineatum on their detectability for avian predators. Great tits (Parus major) were trained to eat sunflower seeds hidden inside the emptied exoskeletons of pale or red G. lineatum. Then the detection time for both colour forms was measured in a dry vegetation environment.

3. The birds required a longer time to find the pale form of G. lineatum than the red one. The pale form appears more cryptic on withered late summer vegetation than the red form, not only to the human eye but also to avian predators. The result supports the idea that the adult individuals of G. lineatum undergo a functional change from a cryptic protective coloration to an aposematic one.

Place, publisher, year, edition, pages
2010. Vol. 35, no 5, 602-610 p.
Keyword [en]
Antipredatory defence, aposematism, background matching, crypsis, great tit, ontogenetic colour change, Parus major, warning coloration
National Category
Behavioral Sciences Biology
Research subject
Ethology
Identifiers
URN: urn:nbn:se:su:diva-47155DOI: 10.1111/j.1365-2311.2010.01219.xOAI: oai:DiVA.org:su-47155DiVA: diva2:373421
Available from: 2010-11-30 Created: 2010-11-30 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Seasonal change in defensive coloration in a shieldbug
Open this publication in new window or tab >>Seasonal change in defensive coloration in a shieldbug
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Protective coloration such as aposematism and crypsis occurs in many insects but only a few species alter their defensive strategy during the same instar. We hypothesize the adult shield bug Graphosoma lineatum with an alternating black and non-melanised longitudinal striation exhibit such a change in defensive coloration. In Sweden, the non-melanised stripes of the pre-hibernation G. lineatum are pale brown and cryptic but they change during hibernation to red and aposematic. We have tested the adaptive functions of coloration of the two G. lineatum forms against bird predators. In Paper I we used great tits as predators and measured detection time of the two forms against a background of dry grass and plants, simulating late-summer conditions. We found that the birds took longer time to find the pale than the red form. Thus, the pale form of G. lineatum is more cryptic in a dry environment than the red form. In Paper II and III we used naïve predators and measured attack rate/latency on red and pale adults and fifth-instar larvae (black and brown) to investigate avoidance and generalisation between the stages. In Paper II domestic chicks initially found the red form most intimidating, but both adult forms are more intimidating than the larva. Moreover, there was a broad generalisation among forms. In Paper III naïve great tits did not find the red form significantly more aversive than the pale adult. Neither the chicks nor the tits showed any difference in the speed of avoidance learning between the two adult colour forms. In Paper IV the shieldbugs themselves were the main focus as we compared activity levels in the different colour forms and found that G. lineatum alters behaviour in accordance to their protective strategy. Thus they were significantly less active during the cryptic phase. Taken together, these experiments suggest that the pale brown adult invests in a cryptic strategy at the cost of reduced protection from aposematism, whereas the red adult benefits from aposematism at the cost of reduced camouflage.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2011. 26 p.
Keyword
Shield bug, colour change, protective coloration, cryptic, aposematic, behavioural change
National Category
Behavioral Sciences Biology
Research subject
Ethology
Identifiers
urn:nbn:se:su:diva-62466 (URN)978-91-7447-373-5 (ISBN)
Public defence
2011-11-02, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
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Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted. Available from: 2011-10-11 Created: 2011-09-20 Last updated: 2011-09-26Bibliographically approved

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Johansen, Aleksandra I.Gamberale-Stille, GabriellaTullberg, Birgitta S.
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