The globe thistle habitat and attachment of Macrolophus pygmaeus on leaves of three Echinops species

Echinops plants, a genus of globe thistles, have proven to be highly attractive to various arthropods in the field. They offer a complex, three-dimensional, and pubescent terrain that is conducive to omnivorous predatory mirid bugs, such as Macrolophus pygmaeus, and related species within the subfamily Bryocorinae (Heteroptera, Miridae), where many other entomophagous insects may struggle. A microscopic examination of the leaf surfaces of 20 Echinops accessions across five species and one subspecies revealed differences in their microstructural features. Echinops bannaticus, Echinops exaltatus, and Echinops sphaerocephalus were selected for detailed evaluation and included in traction force measurements with female M. pygmaeus to compare the bug's attachment on different plant surfaces. These insects demonstrated significantly stronger attachment to the leaves compared to glass, generating forces that were 47 to 12 times their body weight, respectively. The abaxial leaf surfaces, which are covered by a dense layer of tomentous trichomes, provided superior footholds compared to the adaxial glabrous or pruinose leaves. The larger the area covered with tomentous trichomes, the higher the safety factor (attachment force normalised by the bug's body weight) for the insects. In addition, the number of pulling movements decreased on glandular trichomes, likely to avoid being trapped by glandular secretion. This study provides further evidence of the essential role of the interaction between plant surfaces and insect integuments in insect–plant relationships. Insect settlement on plants depends on having proper footholds, which are influenced by surface properties. Consequently, these factors warrant more attention in future research on insect evolution, ecology, and pest management.