Morphological and Behavioral Adaptations of Silk-Lovers (Plokiophilidae: Embiophila) for Their Lifestyle in the Silk Domiciles of Webspinners (Embioptera)

Abstract

The diversity of true bugs gave rise to various lifestyles, including gaining advantage from other organisms. Plokiophilidae are cimicomorphan bugs that live in the silk constructions of other arthropods. One group, Embiophila, exclusively settles in the silk colonies of webspinners (Embioptera). We investigated the lifestyle of Embiophila using microscopy to study the micromorphology and material composition of the leg cuticle, choice assays and retention time measurements based on different characteristics of the embiopteran galleries and tilting experiments with different substrates to quantify the attachment performance of the bugs. Embiophila neither explicitly preferred embiopteran presence, nor required silk for locomotion, but the bugs preferred fibrous substrates during the choice experiments. The hairy attachment pad on the tibia showed the best attachment performance on substrates, with an asperity size of 1 µm. Additionally, very rough substrates enabled strong attachment, likely due to the use of claws. Our findings suggest that Embiophila settle in galleries of webspinners to benefit from the shelter against weather and predators and to feed on mites and other intruders. The combination of behavioral and functional morphological experiments enables insights into the life history of these silk-associated bugs, which would be highly challenging in the field due to the minute size and specialized lifestyle of Embiophila.

Kinematics and coordination of moth flies walking on smooth and rough surfaces

“…For instance, the different sandpapers may be fabricated using different materials that might vary in terms of micro‐asperities in the abrasive grains that could provide footholds. These differing materials might also vary in terms of their material properties, which could interact with the attachment mechanisms of the feet in different ways 46–52 . These factors are likely important contributing factors to variation in locomotion across treatments but are beyond the scope of the present investigation.…”

“…These differing materials might also vary in terms of their material properties, which could interact with the attachment mechanisms of the feet in different ways. [46][47][48][49][50][51][52] These factors are likely important contributing factors to variation in locomotion across treatments but are beyond the scope of the present investigation. However, we note that we most often observed fly feet sliding off abrasive grains in each treatment rather than engaging with them.…”