Unique Fine Morphology of Mouthparts in Haematoloecha nigrorufa (Stål) (Hemiptera: Reduviidae) Adapted to Millipede Feeding

Abstract

Millipede assassin bugs are a diverse group of specialized millipede predators. However, the feeding behavior of Ectrichodiinae remains poorly known, especially how the mouthpart structures relate to various functions in feeding. In this study, fine morphology of the mouthparts and feeding performance of Haematoloecha nigrorufa (Stål, 1867) was observed and described in detail for the first time. The triangular labrum is divided by a conspicuous transverse membrane into a strongly sclerotized basilabrum and a less sclerotized distilabrum. Fifteen types of sensilla are distributed on the mouthparts. Each mandibular stylet has an expanded spatulate apex and about 150 approximately transverse ridges on the external middle side; these help in penetrating the ventral trunk area and the intersegmental membranes of millipede prey. The right maxilla is tapered. On the internal surface are a row dorsal short bristles near the apex and a row of ventral bristles preapically. A longitudinal row of long lamellate structures extend proximate for a considerable distance, lie entirely within the food canal, and bear several short spines and short bristles. There is no obvious difference between males and females in the distribution, number, and types of sensilla on mouthparts. The adult feeding process involves several steps, including searching and capturing prey, paralyzing prey, a resting phase, and a feeding phase. The evolution of the mouthpart morphology and the putative functional significance of their sensilla are discussed, providing insight into the structure and function of the mouthparts adapted for millipede feeding.

Ultrastructural Variations of Antennae and Labia Are Associated with Feeding Habit Shifts in Stink Bugs (Heteroptera: Pentatomidae)

“…In Asopinae, the shape of stylet bundle was modified into the carnivore type, characterized as mandibles with sharp or even hook-like teeth and maxillae with sharp barbs, which might be an adaptation to their carnivorous feeding habit evolved independently ( Figure 9 and Figure S1 ). The mandibles of true bugs are often apically ornamented with various shaped teeth to facilitate penetration and anchoring of food [ 4 , 60 ]. It has been observed that the predatory stink bugs are capable of holding intensively struggling preys during predation [ 61 ] (e.g., personal observations of Eo .…”

Microstructural Adaptation for Prey Manipulation in the Millipede Assassin Bugs (Hemiptera: Reduviidae: Ectrichodiinae)

“…Another group of specialized predators of millipedes that paralyze the preys by injecting toxin are the millipede assassin bugs (Hemiptera: Reduviidae: Ectrichodiinae). Ectrichodiinae is a diverse clade with more than 700 known species, and at least 14 species in 13 genera of this group have been observed to feed on millipedes [5,6].…”

“…First, detecting prey-derived chemical cues to locate prey from a long distance requires the assistance of olfactory sensory organs [7][8][9]. Second, millipedes are usually armed with chemical defenses and hard, smooth body walls, and are often much larger than these assassin bugs, which makes them difficult to be manipulated [5,6,9,10]. Previous studies have demonstrated several behavioral adaptation and morphological innovations which help millipede assassin bugs to cope with the challenges of prey localization and manipulation.…”

Labial Sensory Organs of Two Leptoglossus Species (Hemiptera: Coreidae): Their Morphology and Supposed Function

“…Thus far, the morphology and ultrastructure of the labial receptors of true bugs have been studied in several species within families: Nepomorpha [ 18 , 25 , 26 ] Gerromorpha [ 18 , 27 ], Cimicomorpha [ 24 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ], and Pentatomomorpha [ 32 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ]. Within the Coreoidea superfamily, labial sensilla have been studied on a single species of Rhopalidae, Rhopalus maculatus (Fieber, 1837) [ 32 ], and two species of Alydidae: Neomegalotomus parvus (Westwood, 1842) [ 48 ] and Riptortus pedestris (Fabricius, 1775) [ 42 ].…”