## 4 Discussion and Conclusions  
The larvae of these specialized troglobiotic (cave-adapted) carabid are difficult to find, even in the caves where adult individuals are abundant [10; 30] (O.T.M., personal observations). Yet, another difficulty is to determine the presence or absence of sets or pores under an optical microscope for comparison with the classical description [2; 15; 18]. From our observations, the breaking of the setae at the time of collection and preparation can lead to confusion in identifying the pores and determining the number of setae under the optical microscope. Despite their importance, there are a few studies related to the ultrastructural organization of the head and appendages, as well as the sensilla present on these structures [22; 23; 24; 25; 26]. The larval morphology of the _Duvalius_ larvae described in this paper conforms to the diagnosis of the Trechini by the absence of lacinia, presence of one claw, division of the apical palpal segments into apparent segments [7; 13; 18; 31; 32; 33; 34] and chaetotaxy [35]. The _Duvalius_ larvae also have a set of apical and subapical sensilla on the antennae that are characteristic of the tribe [7], and the presence of secondary setae on the frontal part of the cephalic capsule [20]. The main morphological differences between the _Duvalius_ larvae were considered to be the length/width ratio of the cephalic capsule, the shape of the nasale and slight differences in the development of setae [10]. These differences were also observed in the two described larvae, although it is not certain that they are individual variations and do not reflect inter-species variations. Therefore, we analyzed microstructures of _Duvalius_ larvae, frequently overlooked due to the lack of SEM analysis, and that can provide more reliable taxonomic characters. The two larvae described here, _D. subterraneus_ and _D. paroecus_, have a different chaetotaxy of the cephalic capsule (Figures 9 and 11). These fine structures, such as nasale, number and arrangement of setae on the mandible or sensilla complex, represent structural elements of taxonomic importance and show the specialization of an organ such as the mandible, antenna and labium to subterranean microhabitats. The larvae are often found under rocks, in wet conditions, even inside the caves. The quiescence on the head and body, and the densely pubescent labium, shows possible adaptation to life on muddy soil and water film on a periodically flooded cave floor [14] or in \"terrestrial-phreatic habitats\" according to [PERSON] [17]. The role of pubescence is to retain air bubbles in immersion conditions and to ensure floating [36]. The labial brushes observed in the two described larvae have multiple digitiform branches that increase the retention capacity of the organic particles from water [37], as also described in cave Leptodirini [38]. The nasale (2 I-K, 10 G-I) of the two species presents structural differences. The nasale of _D. subterraneus_ is more prominent than of _D. paroecus_. _D. subterraneus_ has seven setae and _D. paroecus_ has eight. The nasale of the two species is tri-lobed (a central lobe and two lateral lobes). Each lobe has several small lobes at a fine structural level. These small lobes differ in number and shape between the two species. The central lobe of the two species is a formation consisting of two layers. The _D. subterraneus_ first layer has four small lobes on each side. In the anterior part, between the two NA7 setae, the nasale has a slightly more prominent small lobe. The small lobes have a rounded apical part. The _D. paroecus_ first layer has three small lobes on each side. The small lobes have a sharp apical part. The anterior small lobe (between the two NA8) is rounded and slightly contoured. TheD. subterraneus second layer is an irregular formation in the anterior part. Laterally, there are three small, slightly contoured lobes on each side. The _D. paroocus_ second layer is well contoured with five small sharp lobes on each side.