First description and comparison of the morphological and ultramicro characteristics of the antennal sensilla of two fir longhorn beetles

Abstract

Allotraeus asiaticus Schwarzer and Callidiellum villosulum Fairmaire are repeatedly intercepted in wood and wood products all over the world. As two common stem borers of Cunninghamia lanceolata (Lambert) Hooker, to further understanding of the differences in their living habits, behaviors and the mechanism of insect-host chemical communication, we observed the external morphology, number and distribution of antennal sensilla of A . asiaticus and C . villosulum with scanning electron microscopy (SEM), respectively. The results showed that 1st-5th subsegments of the flagellum are spined endoapically in A . asiaticus which is different from the previous report (1st-3rd of the flagellomere). Meanwhile, there were five subsegments on the flagellum of C . villosulum that were clearly specialized as serrated shapes on the 4th-8th flagellomeres. Four types (ten subtypes) of sensilla were both found on the antennae of these two fir longhorn beetles, named Böhm bristle (Bb), sensilla trichodea (ST I and II), sensilla basiconica (SB I, II and III), sensilla chaetica (SCh I, II, III and IV). There is one additional kind of morphological type of sensilla found on the antennae of C . villosulum compared to A . asiaticus which was related to their habit of laying eggs only on dry and injured fir branches, named sensilla campaniformia (SCa). These differences may vary according to their own biological habits. For research purposes, the observed difference in the sensillum distribution and function between the two fir longhorn beetles will greatly facilitate the design of better semiochemical control methods of these insect pests.

The Cellulolytic Bacteria Associated with Gut of Longhorn Beetle, Prionomma bigibbosum (Coleoptera: Cerambycidae): an Electron Microscopic Study

“…The beetle being a non-feeding adult, it is apparent that the bacterial units in the electron micrograph constitute autochthonous microbiota, confirming our hypothesis [36]. In other studies, the autochthonous microbiota of the coleopteran gut was found to assist in the production of various hormones such as semiochemicals [37] and sex pheromone in Dendroctonus terebrans hindgut [38]. The number, distribution, and position of antennal sensilla are very crucial for semiochemicals and chemo-receptions in longhorn beetles.…”

Revisiting trends in morphology of antennal sensilla in scarabaeoid beetles

“…We expect that chemical communication is rather more complex than it would become apparent from the simple examination of sensilla morphology. Sensilla trichodea prevail also in all hyperdiverse phytophagous beetle lineages of Phytophaga with no increased antennal surface (e.g., Ritcey and McIver 1990;Ranger et al 2017;Vera and Bergmann 2018;Di Palma et al 2019;Dong et al 2020), thus high performance in chemical sensing is not necessarily linked with complicated or highly modified sensilla structure (e.g., Symonds et al 2011). For instance, Rutelinae and Melolonthinae, although having in many lineages quite similar placoid sensilla, differ completely in their pheromone compounds (Melolonthinae: amino acid derivatives and terpenoids; Rutelinae: fatty acid derivatives; Leal 1998).…”

Scanning electron microscopy of sensilla on the labial and maxillary palps of adult Callidiellum villosulum Fairmaire (Coleoptera: Cerambycidae)

“…Previous studies have also shown that the density of sensors is closely related to sensing function (Dong, Dou, et al, 2020; Hu et al, 2020). The Sh II was present at a greater density on the last segment of the labial palps in of females than that of males because female adults need frequent vibrations to acquire feedback from bark when they lay eggs, which was similar to their description on the antennae (Dong, Dou, et al, 2020).…”

“…Larval emergence peaks from late March to early April (Nakamura & Kojima, 1981), and adults usually appear from March to May (Cocquempot & Mifsud, 2013). The morphological characteristics of adult C. villosulum have been described in detail (Dong et al, 2020). Callidiellum villosulum beetles are approximately 7–11 mm in length (Cocquempot & Mifsud, 2013).…”

“…Their elytra are entirely testaceous to slightly bronze, and they possess brown‐yellow spots on their wings and dark brown long hairs on their backs and tails (Cocquempot & Mifsud, 2013). In recent years, some studies have not only described the behavior of C. villosulum (Wickham et al, 2016) but also combined the sensilla and behavioral characteristics of this beetle from a micro perspective (Dong, Dou, et al, 2020). A previous study, by performing a scanning electron microscopy (SEM) observation of the antennae of adult C. villosulum , found that the antennae of this species have obvious sexual dimorphism and explained the difference in behavior between sexes on the basis of antennae (Dong, Dou, et al, 2020).…”