Ultrastructure and distribution of sensilla on the maxillary and labial palps ofChlorophorus caragana(Coleoptera: Cerambycidae)

Observations on the ultrastructure of the oral appendages of Glenea cantor Fabricius (Coleoptera: Lamiinae)

Using scanning electron microscopy, we examined the gross and ultrastructure morphology of the mandibles, labial palpi, and mandibular palpi of adult male and female Glenea cantor beetles. The morphology of these parts, both in their gross and ultrastructure, varied significantly between males and females. The lengths of the mandible, labial palpi, and mandibular palpi were clearly noticeably longer in females than in men, which is mostly related to the oviposition mechanism. In terms of the ultrastructural morphology of the mandibles, labial palpi, and mandibular palpi, seven types of sensilla were found on these parts: sensilla twig basiconica (STB I, II, III, and IV), sensilla chaetica (Scheme IV and V), Böhm's bristles (Bb), sensilla placodea (SP), sensilla trichodea (ST II), sensilla plate (SP), sensilla coeloconica (SC), and sensilla campaniformia (SCa). Females have significantly more ST I and Scheme III on their mandibles than males. The mechanical sensors SCh and Bb, olfactory sensor ST II, taste sensor STB IV, and carbon dioxide sensor and temperature and humidity sensors SC, SP, and SCa were much more developed on the labial and maxillary palpi of females compared to those of males, which further clarified the significance of the oral appendages in oviposition behavior. These findings will advance information-based technique design and the creation of information-based pest control strategies by assisting in our understanding of the host preference and oviposition behavior of adult G. cantor. RESEARCH HIGHLIGHTS: The external morphology and distribution of the oral appendages of Glenea cantor between sexes has been researched through scanning electron microscopy (SEM) for the first time. Several significant differences between males and females have been found by analyzing the oral appendages of G. cantor with SEM. The differences in the structure of oral appendages of G. cantor between sexes reflect functional differences in reproductive behaviors.

Functional morphology of the mouthparts of longhorn beetle adult Psacothea hilaris (Coleoptera: Cerambycidae) and sensilla comparisons between the sexes

Psacothea hilaris is an important wood boring beetle that causes significant ecological and economic damage. The mouthparts of P. hilaris contain feeding and sensory structures that play important roles in many behaviors. The study of their functional morphologies provides insight into feeding and sensory mechanisms. The fine structures of the mouthparts and the sensilla of both sexes were observed by scanning electron microscopy, with special attention to quantitative comparisons. The general structures of the mouthparts are similar in males and females. However, the maxillary and labial palps of females are more well-developed than those of males. Six types of sensilla were found in both sexes: sensilla basiconca, sensilla trichodea, sensilla chaetica, sensilla digitiformia, sensilla coeloconica, and sensilla palmata. This was the first attempt to describe the sensilla on the epipharynx and ligula of Cerambycidae. There were differences in the number of sensilla of males and females, especially on the mandibles, maxillary and labial palps. However, not all types of sensilla have a greater number in females compared to males. The results provide basic information on the gustatory sensation mechanism of Cerambycidae.

Morphological comparison of the sensilla on the maxillary and labial palps between male and female adults of Moechotypa diphysis (Coleoptera: Cerambycidae)

Moechotypa diphysis (Pascoe) is one of the most important pests in agriculture and forestry. However, there are few studies focusing on the external morphology of M. diphysis adults. In this study, the mouthparts of M. diphysis adults were observed by the scanning electron microscope to compare the quantity and distribution of the sensilla on the maxillary and labial palps. The results showed that there are four segments on the maxillary palps and three segments on the labial palps. The length of each segment of the maxillary and labial palps is larger in the female than that in the male. Six types of sensilla are found on the maxillary and labial palps of M. diphysis adults: sensilla basiconca (SB1, 2, 3, and 4), sensilla trichodea (ST1, 2 and 3), sensilla chaetica (SC), sensilla placodea (SP), hair plate (HP) and sensilla coeloconica (SCo). There is no significant difference in the number of most types of sensilla between females and males in the same position. However, the number of ST1 on the maxillary and labial palps is significantly higher in the female than in the male. In addition, the number of most types of sensilla (SB2, ST1, SC, SP, HP, and SCo) on the maxillary palps is significantly higher than on the labial palps both for females and males. Maxillary palps may play a more important role in the activities of M. diphysis adults than the labial palps. Based on this study, we discussed the functions of the sensilla on the maxillary and labial palps of M. diphysis adults to provide the theoretical basis and statistical data for further research on the behavior and the electrophysiology of this devastating forest pest.

Mouthpart structure of the adult Bicaubittacus appendiculatus () (Mecoptera: Bittacidae)

The structure and functional morphology of the mouthparts were investigated in adult hangingfly Bicaubittacus appendiculatus (Esben-Petersen, 1927) by scanning electron microscopy and histological serial sections. The mandibulate mouthparts consist of a labrum-epipharynx, paired mandibles and maxillae, and unpaired labium and hypopharynx. The labrum is elongated and tapered toward the apex. The epipharynx is furnished with numerous sensilla. The mandibles are sword-shaped, with an outer sharp tooth curved mesad and an inner blunt corner. The basal region of each mandible processes a conical projection. The maxillae are well-developed, each consisting of a sclerotized cardo, an elongated stipes, which bears an inner lacinia, an outer galea, and laterally a five-segmented maxillary palp. The labium is formed by a postmentum, a prementum and a pair of two-segmented labial palps. The hypopharynx is concave inward on the anterior side, with numerous microtrichia on the posterior surface. Seven types of sensilla were found on the mouthparts: sensilla basiconica on the epipharynx, and maxillary and labial palps; sensilla chaetica on the epipharynx; sensilla palmata, sensilla placoidea and sensilla trichodea on the epipharynx and maxillary palp; sensilla campaniformia and hair plates on the basal joints of palps. The sensillar function and the feeding mechanism of mouthparts in bittacids are briefly discussed.

Morphology and distribution of antennal sensilla in the gall midge Gephyraulus lycantha (Diptera: Cecidomyiidae)

The gall midge Gephyraulus lycantha (Diptera: Cecidomyiidae) is a serious gall-forming pest that causes devastating damage in the wolfberry, Lycium barbarum (Solanaceae) in Northwest China. In the present study, the external morphology and ultrastructure of the antennae and the antennal sensilla of G. lycantha were examined by scanning electron microscopy. The results show that the moniliform antenna of G. lycantha consisted of a scape, pedicel, and flagellum, and exhibited obvious sexual dimorphism. The male antennae were significantly longer than those of females. Moreover, male flagellomeres were spheroidal nodes separated by slender internodes, whereas those of females were cylindrical with no obvious internodes. There were sex and individual differences in antennal segment number. Male antennae had 10 - 16 flagellomeres, most of which had 15, while female antennae consisted of 8 - 14 flagellomeres, most of which had 12. Moreover, a pair of antennae in the same individual had different numbers of flagellomeres. Four types of sensilla were observed along the surface of the antennae, including sensilla chaetica, sensilla trichodea, sensilla coeloconica, and sensilla circumfila. Among the types of sensilla, sensilla chaetica were the longest and most prominent sensilla discovered on the antennal flagellum in both sexes. Sensilla trichodea were widely distributed over the antennal surface, including the scape, pedicel, and flagellum. Sensilla coeloconica were categorized into four subtypes: sensilla coeloconica Ⅰ, sensilla coeloconica Ⅱ, sensilla coeloconica Ⅲ, and sensilla coeloconica IV; however, sensilla coeloconica IV was absent in females. Sensilla circumfila were found only on cecidomyiidae insect antennae and were attached to the surface by a series of stalks, forming loops around each flagellomere. The numbers of all four types of sensilla on the male antennal windward side were significantly higher than those on the leeward side. The probable biological functions of these sensilla were discussed herein based on their morphology and ultrastructure. These results provide an important basis for further research on chemical communication and strategies for the control of G. lycantha, and it will be able to serve future group Taxonomy studies (species of cecidomyiidae), providing new taxonomic characters (general ultrastructural morphology, number of sensilla and antennal segments, distribution of different types of setae, types and subtypes sensilla), which varies between species and subspecies.

Morphology and distribution of sensilla on the antennae and ovipositor of the Hymenopteran parasitoid Pseudotorymus jaapiellae Yang et Chen

Pseudotorymus jaapiellae is an important ectoparasitoid of the larvae of Gephyraulus lycantha, a serious gall-forming pest that devastates wolfberry, Lycium barbarum, in Northwest China. To provide requisite background for our ongoing research on the mechanisms of P. jaapiellae's host location and subsequent oviposition, we used scanning electron microscopy to describe the external morphologies and distributions of sensilla on their antennae and ovipositors. The geniculate antennae of both male and female P. jaapiellae were each composed of a scape with a basal radiculum, a pedicel, an anellum and a flagellum. We identified nine morphological sensilla types on the antennae of both sexes, including three sensilla trichodea (ST), one sensillum basiconicum (SB), two sensilla chaetica (SCh), one sensillum placodeum (SP), one sensillum coeloconicum (SCo), and one sensillum campaniformia (SCa). Females had significantly more ST I and SP than males had, but males had more ST III than did females. We observed six types of sensilla on the ovipositor, including three ST, one SB, and two SCa. ST II, ST IV and SB II were on the sheath, whereas ST V and the SCa were on the stylus. Finally, the possible biological functions of these sensilla were discussed according to their morphology and ultrastructure. These results provide an important basis for further study on chemical communication between P. jaapiellae and their host, and contribute to the development of a biological control program for G. lycantha, using the parasitoid, P. jaapiellae.

Ultrastructural Analysis of Mouthparts of Adult Horn Fly (Diptera: Muscidae) From the Brazilian Midwest Region

The ultrastructure of the mouthparts of Haematobia irritans (L.) was investigated by scanning electron microscopy. The morphological characteristics of the maxillary palps, labium (prementum and postmentum), labrum, hypopharynx, haustellum, and labellar lobes are described, as well as of the sensilla evidenced on all the surface of the mouthparts, and the set of different positions assumed by the mouth apparatus of this fly. Based on their morphology, 12 well-differentiated sensilla were identified, among three types of cuticular sensilla: trichoidea, coeloconica, and campaniformia. A slight sexual dimorphism in the sensilla patterns found in the mouthparts of H. irritans was evidenced. These observations are discussed with reference to the current literature on the functional morphology of sense organs of Insecta. These results could facilitate the recognition of the chemosensory sensilla by electrophysiological techniques, and foment future taxonomic and phylogenetic studies to better elucidate the evolution of Diptera, Muscomorpha.