Ava Joa- Year 3
Abstract
Due to many of the lasting effects of modern pesticides, there has been a growing push to develop more ecologically friendly alternatives. This paper examines the possible applications of necropheremones and discusses their potential effects of creating avoidance in insects after its administration to organic compounds. Over a course of 10 tests, it was examined whether the presence of oleic acid in provided food would reduce its consumption when introduced to Madagascar Hissing Cockroaches. Analysed results demonstrated a negative correlation between the presence of the acid and the percent mass of food consumed, affirming the repulsive properties of the acid in comparison to the foraging instinct. This experiment aims to serve as a microcosm of greater applications for the use of replicant pheromones in agriculture.
Introduction
Many insects such as bees, ants, cockroaches, and collembola have been known to demonstrate ‘necromone’ driven behaviours, actions driven as a response to pheremones released during the decomposition of other insects. (Yao et al., 2009) For social insects, this manifests as the sanitary practice of removing dead members of the colony away from the communal living areas to prevent the spread of disease and parasitic transmission. (IBID) For solitary insects, this becomes an extreme avoidance—necrophobic behaviour—theorised to be an attempt to reduce the risk of predation by avoiding potentially dangerous territory. (IBID) An early study on necrophoric behaviour in harvester and fire ants determined that these sanitary behaviours could be triggered solely by the presence of just the oleic acid itself rather than the physical corpse, as well as living ants being regarded as corpses by their nestmates after being coated with a thin layer of the acid (Wilson et al., 1958). In addition, research conducted with cockroaches displayed that they would avoid potential shelters lined with pheremonally treated filter paper. During these tests, the paper was soaked in a hexane solution containing the bodies of several freshly killed cockroaches, and left for a period of 3 days. Following a bioassay, it was determined that oleic and linoleic acid were the most prominent of the four fatty acids present in the infused solution. Similar reactions to oleic acid have been found in both ants and bees, and could serve as a universal signal for death-recognition in insects (Rollo et al., 1994). Standard pesticides and insecticides, both those used domestically and in agriculture can lead to the unintended pollution of the air, water, and soil, leading to lasting harm to both non-target organisms, and the greater surrounding environment (BCMAFF, 2017). Insect pheromones have been proposed as ecologically friendly alternatives to chemical pesticides, due to their lack of toxicity and benign environmental effects (Rizvi et al., 2021). Studies conducted with insect sex pheromones found potential applications into communication disruption, mass trapping and luring insects to designated areas (Kirsch, 1998).
Materials and Methods
In a series of 10 tests, an approximately 40 litre terrarium of Madagascar Hissing Cockroaches (Gromphadorhina portentosa) was introduced to two petri dishes of approximately 30 grams of mashed banana mixture between the hours of 8:00 and 9:00 pm. One petri dish was left unaltered to serve as a control, and was weighed and recorded in a data chart as ‘initial control mass.’ It was then placed on the lower left corner of the terrarium. The other dish was treated with 2ul of Oleic Acid (Merlan Scientific), which was lightly mixed into the mashed banana via a small stirring rod. The test dish was then weighed and recorded in the data table as ‘initial test mass’ before being placed in the upper right hand corner of the terrarium. Following the introduction of the dishes, the lights were turned off to best mimic the cockroaches nocturnal feeding habits. The cockroaches were then re-visited at 7:30 am the following morning, and both dishes were re-weighed. These new weights were recorded in the data table as ‘final control mass’ and ‘final test mass.’ This trial was then repeated a total of 10 times to attain more statistically relevant results. Once all experimental data was collected, percent mass loss was calculated for the control and active test of each trial and presented in a scatter plot graph. In order to minimise confounding variables, a desiccation test was conducted following the active tests involving the cockroaches. The desiccation test measured the mass change of a mashed banana sample outside of the terrarium, to determine the natural desiccation due to moisture loss. This data was converted into percent mass change and factored into the previous results for greater accuracy.
Figure 1. Set up of the testing tank
Data
Table 1. Raw Data
| Trial # | Test Initial(g) | Test Final(g) | Mass Change (g) | Control Initial(g) | Control Final(g) | Mass Change(g) |
| 1 | 36.46 | 35.54 | -0.92 | 28.00 | 24.27 | -3.75 |
| 2 | 28.7 | 27.35 | -1.35 | 21.41 | 11.91 | -9.50 |
| 3 | 35.71 | 33.76 | -1.95 | 35.28 | 30.9 | -4.38 |
| 4 | 25.22 | 22.43 | -2.79 | 26.44 | 20.78 | -5.66 |
| 5 | 29.6 | 23.26 | -6.34 | 29.07 | 19.03 | -10.04 |
| 6 | 28.21 | 23.47 | -4.74 | 25.44 | 20.42 | -5.02 |
| 7 | 31.84 | 30.84 | -1.00 | 30.94 | 28.05 | -2.89 |
| 8 | 30.21 | 29.29 | -0.92 | 29.72 | 26.58 | -3.14 |
| 9 | 35.81 | 32.94 | -2.87 | 35.4 | 29.19 | -6.21 |
| 10 | 26.22 | 25.24 | -0.98 | 21.81 | 14.35 | -7.46 |
| Average | 30.79 | 28.41 | -2.39 | 28.35 | 22.55 | -5.81 |
Calculations
Table 2. Calculated Percent Mass Change
| Trial # | Test Percent Mass Loss (%) | Control Percent Mass Loss (%) |
| 1 | 0.025 | 0.133 |
| 2 | 0.047 | 0.444 |
| 3 | 0.055 | 0.124 |
| 4 | 0.111 | 0.214 |
| 5 | 0.214 | 0.345 |
| 6 | 0.168 | 0.197 |
| 7 | 0.031 | 0.093 |
| 8 | 0.030 | 0.106 |
| 9 | 0.080 | 0.175 |
| 10 | 0.037 | 0.342 |
| Average | 0.080 | 0.217 |
Figure 2. Percent Mass
Figure 3. Box Plot of Percent Mass
Results
After the raw data obtained from the experiment was converted into percent mass loss to produce the values displayed in the graph above. The untreated (control) dish displayed higher mass reduction over each conducted test, meaning that more of the bait mixture was consumed over the 8 hour period over which the test was conducted. Following the conduction of the desiccation tests, it was determined solely approximately 0.028% of the banana’s mass reduction was due to moisture loss.
Discussion
Following the conversion of raw collected data to percent mass change, it can be seen that the inclusion of oleic acid to the provided food mixture led to a overall lessened mass change, and increased avoidance of the treated dish. This corroborates previous research, and the initial hypothesis—demonstrating the repulsive effects of oleic acid for insects—and asserting that the sanitary instinct surpasses that of foraging. Further research could refine the understanding of this relationship, and it’s potential applications to agricultural contexts. As it has been shown that the presence of oleic acid results in a lessened attraction to provided food sources, oleic acid presents itself as a viable potential biopesticide due to its benign effects on the surrounding environment. In addition, this experiment demonstrated the pre-eminent nature of the sanitary instinct, providing further support for future research regarding pheremonal replacements for pesticides. Further experimentation could explore the acid’s effect on necessary insects such as pollinators, as well as the timeline of its efficacy. Unfortunately the timeframe during which this experiment was conducted limited the amount of possible trials, leading to a reduced number of conductions, which may have limited the potential legitimacy of results. In addition, the testing tank used was of a limited size, leading to potential saturation of the pheremonal residue throughout the tank. Future experiments would seek to increase both the size of the terrarium and number of trials conducted in order to receive the most accurate results. Inconsistencies in the data above, such as in trials #2 and #10 are likely due to changing levels in appetite, however further testing would be needed to determine this.
Works Cited
Environmental Protection and Pesticides. BC Ministry of Agriculture, Apr. 2017, https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/agriculture-and-seafood/animal-and-crops/plant-health/environmental-protection-and-pesticides.pdf.
Kirsch, P. (1988). Pheromones: Their potential role in control of agricultural insect pests. American Journal of Alternative Agriculture, 3(2-3), 83.doi:10.1017/s0889189300002241
Rizvi, S. A. H., George, J., Reddy, G. V. P., Zeng, X., & Guerrero, A. (2021). Latest Developments in Insect Sex Pheromone Research and Its Application in Agricultural Pest Management. Insects, 12(6), 484. https://doi.org/10.3390/insects12060484
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Wilson, E. & Durlach, N. & Roth, L.. (1958). Chemical Releaser of Necrophoric Behavior in Ants. Psyche, Camb.. 65. 10.1155/1958/69391.
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