Floral and Bird Excreta Semiochemicals Attract Western Carpenter Ants

Abstract

Ant colonies have vast and diverse nutritional needs but forager ants have limited mobility to meet these needs. Forager ants would accrue significant energy savings if they were able to sense and orient toward odor plumes of both carbohydrate and protein food sources. Moreover, if worker ants, like other flightless insects, had reduced olfactory acuity, they would not recognize the specific odor signatures of diverse carbohydrate and protein sources, but they may be able to orient toward those odorants that are shared between (macronutrient) food sources. Using the Western carpenter ant, Camponotus modoc, as a model species, we tested the hypotheses that (1) food sources rich in carbohydrates (aphid honeydew, floral nectar) and rich in proteins (bird excreta, house mouse carrion, cow liver infested or not with fly maggots) all prompt long-distance, anemotactic attraction of worker ants, and (2) attraction of ants to plant inflorescences (fireweed, Chamaenerion angustifolium; thimbleberry, Rubus parviflorus; and hardhack, Spiraea douglasii) is mediated by shared floral odorants. In moving-air Y-tube olfactometer bioassays, ants were attracted to two of four carbohydrate sources (thimbleberry and fireweed), and one of four protein sources (bird excreta). Headspace volatiles of these three attractive sources were analyzed by gas chromatography-mass spectrometry, and synthetic odor blends of thimbleberry (7 components), fireweed (23 components), and bird excreta (38 components) were prepared. In Y-tube olfactometer bioassays, synthetic blends of thimbleberry and fireweed but not of bird excreta attracted ants, indicating that only the two floral blends contained all essential attractants. A blend of components shared between thimbleberry and fireweed was not attractive to ants. Our data support the conclusion that C. modoc worker ants can sense and orient toward both carbohydrate and protein food sources. As ants were selective in their responses to carbohydrate and protein resources, it seems that they can discern between specific food odor profiles and that they have good, rather than poor, olfactory acuity.

Effects of macro- and micro-nutrients on momentary and season-long feeding responses by select species of ants

“…Based on mean feeding responses, field colonies of L. niger consumed sucrose and EEAs equally. However, feeding preferences of individual colonies observably differed, with some colonies favoring sucrose and others EAAs 75 . These data indicate that the colonies' preferred macro-nutrient may shift over time in accordance with the colonies' demographics and/or resource availability or competition in their habitat.…”

“…4b; Table S7). Sucrose consumption declined over time, whereas the consumption of sucrose in a binary blend with EAAs increased during the last three sampling dates 75 (Fig. 4b).…”

“…We evaluated the significance of predictors, using likelihood ratio tests and made Tukey adjusted pairwise comparisons between mean proportional consumption values between treatments. Data 75 were analysed and graphed using R (v. 4.2.2) and R studio (v. 2022.07.1 + 554) 76 . Data were processed using functions from the tidyverse 77 and the plyr package 78 .…”

Bait, not reward: CO2-enrichedNepenthespitchers secrete toxic nectar

“…In our field study, ants are the most common prey type in the pitchers of N. khasiana . This observation is in agreement with the previous studies in other native habitats, and the number of ants captured was positively correlated to EFN production (Moran, 1996; Merbach et al ., 2001; Blüthgen and Fiedler, 2004; Di Giusto et al ., 2008; Bauer et al ., 2008; Gaume et al ., 2016; Renyard et al ., 2022). EFN is easily accessible and relatively consistent food source for flightless ants.…”