Interactions betweenAlloxysta brevis (Hymenoptera, Cynipoidea, Alloxystidae) and honeydew-collecting ants: How an aphid hyperparasitoid overcomes ant aggression by chemical defense

AbstractIn April of 1915, the German-Jewish chemist Fritz Haber supervised the first deployment of industrialized chemical weapons against French colonial troops. The uncertain nature of the attack, both in its execution and outcome, led many German military men to question the controllability of poison gas. Over the next three decades, Germans would continue this line of inquiry, as aero-chemical attacks appeared increasingly imminent. This article narrates the German search for control over chemical weapons between the world wars, revealing the ways in which interwar techno-nationalists tied the mastery of poison gas to ethno-racial definitions of Germanness. Under the Nazis, leaders in civilian aero-chemical defense picked up this interwar thread and promoted a dangerous embrace of gas that would supposedly cull the technically superior Germans from other lesser races. Although this vision of a chemically saturated world did not suffuse German society, such logic did play out in the gas chambers of the Holocaust.

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Interactions of ants with native and invasive lady beetles and the role of chemical cues in intraguild interference

Chemoecology ◽

10.1007/s00049-021-00354-4 ◽

2021 ◽

Author(s):

Roman Bucher ◽

Laura M. Japke ◽

Ayse Gül Ünlü ◽

Florian Menzel

Keyword(s):

Chemical Cues ◽

Harmonia Axyridis ◽

Species Recognition ◽

Lady Beetle ◽

Lasius Niger ◽

Beetle Species ◽

Beetle Elytra ◽

Lady Beetles ◽

Ant Aggression

AbstractThe predator-predator naïveté hypothesis suggests that non-native predators benefit from being unknown to native predators, resulting in reduced intraguild interference with native predators. This novelty advantage should depend on the ability of native predators to recognize cues of non-native predators. Here, we compared ant aggression and lady beetle reaction in four native and the invasive lady beetle species Harmonia axyridis. In addition, we tested whether lady beetle cuticular hydrocarbons (CHCs) are involved in species recognition, which might explain naïveté if the invasive species has a specific CHC profile. To this end, we conducted behavioral assays confronting two native ant species with both living lady beetles and lady beetle elytra bearing or lacking CHCs of different lady beetle species. Finally, we characterized CHC profiles of the lady beetles using GC–MS. In general, the aggression of Lasius niger was more frequent than that of Myrmica rubra and L. niger aggression was more frequent towards most native lady beetle species compared to H. axyridis. The removal of CHCs from lady beetle elytra reduced aggression of both ant species. If CHCs of respective lady beetle species were added on cue-free elytra, natural strength of L. niger aggression could be restored. CHC analyses revealed a distinct cue composition for each lady beetle species. Our experiments demonstrate that the presence of chemical cues on the surface of lady beetles contribute to the strength of ant aggression against lady beetles. Reduced aggression of L. niger towards H. axyridis and reduced avoidance behavior in H. axyridis compared to the equally voracious C. septempunctata might improve the invasive lady beetle’s access to ant-tended aphids.

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