Cuticular hydrocarbons of pupae in the ant Formica exsecta

Chemical communication is common across all organisms. Insects in particular use predominantly chemical stimuli in assessing their environment and recognizing their social counterparts. One of the chemical stimuli used for recognition in social insects, such as ants, are long-chain hydrocarbons. Next to providing waterproofing, these surface hydrocarbons serve as a signature mixture, which ants can perceive, and use to distinguish between strangers and colony mates, and to determine caste, sex, or reproductive status of another individual. They can be both environmentally and endogenously acquired. The surface chemistry of adult workers has been studied extensively in ants, yet the pupal stage has rarely been considered. Here we characterized the surface chemistry of Formica exsecta pupae, and examine differences among sexes, castes (reproductive vs. worker), and types of sample (developing individual vs. cocoon envelope). We found quantitative and qualitative differences among both castes and types of sample, but male and female reproductives did not differ in their surface chemistry. We also found that the pupal surface chemistry was more complex than that of adult workers in this species. These results improve our understanding of the information on which ants base recognition, and highlights the diversity of surface chemistry in social insects across developmental stages.

Methods
Date of data collection: 1.6-31.7 2012

Geographic location of data collection: SW Finland, Tvärminne zoological station

1. Methods used for collection/generation of data:

Field collection of ant pupae from 35 colonies, 3-5 individuals per colony
Standard GCMS-analysis on adult workers, pupal cases and corresponding developing individuals inside the pupae. All castes, workers, new queens, and males included

2. Methods for processing the data:

Surface chemicals were extracted by washing each individual (cocoon, and developing individual separately) in HPLC grade pentane, and analysed with an Agilent 7890A GC coupled with an Agilent 5975c MS (described in Pulliainen et al. see above)
Both raw, proportional, and transformed (Aitchison) data are included

3. Instrument- or software-specific information needed to interpret the data:

Excel or other spreadsheet

6. Quality-assurance procedures performed on the data:

Chemical analyses were performed by an experienced technician with a Master in Chemistry; the GC-MS was tuned every day and a cleaning procedure applied every morning. The samples did not contain any contaminations.

7. People involved with sample collection, processing, analysis and/or submission:

Unni Pulliainen, Nick Bos, Patrizia d’Ettorre, Liselotte Sundström