Pinhole Borer Research Articles

The genome sequence of the oak pinhole borer, Platypus cylindrus (Fabricius, 1792)

We present a genome assembly from an individual male Platypus cylindrus (the oak pinhole borer; Arthropoda; Insecta; Coleoptera; Curculionidae). The genome sequence is 147.5 megabases in span. Most of the assembly is scaffolded into 8 chromosomal pseudomolecules, including the X and Y sex chromosomes. The mitochondrial genome has also been assembled and is 19.29 kilobases in length. Gene annotation of this assembly on Ensembl identified 13,468 protein coding genes.

The genome sequence of the oak pinhole borer, Platypus cylindrus (Fabricius, 1792).

We present a genome assembly from an individual male Platypus cylindrus (the oak pinhole borer; Arthropoda; Insecta; Coleoptera; Curculionidae). The genome sequence is 147.5 megabases in span. Most of the assembly is scaffolded into 8 chromosomal pseudomolecules, including the X and Y sex chromosomes. The mitochondrial genome has also been assembled and is 19.29 kilobases in length. Gene annotation of this assembly on Ensembl identified 13,468 protein coding genes.

A new genus and species of Platypodini pinhole borers from South America (Coleoptera, Curculionidae, Platypodinae)

I describe Amplioscapus new genus for Amplioscapus mirabilis new species represented by 164 specimens collected from tropical forests of the Amazon Basin and Guiana Shield. The new genus differs from all other Neotropical Platypodini genera in the antennae being inserted at the upper margin of the eyes in females; in the extraordinarily expanded antennal scape with dense long setae; in the numbers of transverse rugae on the protibiae; and in the numbers of small teeth on the anterior margin of the impression at the distal ends of the metanepisternum and metaventrite. The new pinhole borer genus is most similar to Megaplatypus Wood; in addition to the characters mentioned previously, the new genus differs from all known Megaplatypus in the pair of large mycangia on the female pronotum and the strongly alternating lengths of the elytral interstriae of males. Most individuals were taken from low elevations. Host records for specimens taken from cut trees show the new species to be a host generalist. The vast majority of specimens were captured by flight intercept traps, Malaise traps or canopy fogging, underlining the importance of passive trapping for tropical insect biodiversity surveys.

Identification of the ambrosia beetle Xyleborinus saxesenii (Ratzeburg, 1837) (Coleoptera: Curculionidae: Scolytinae) from frass and adult DNA by TaqMan Probe real‐time‐PCR

AbstractA molecular tool has been set up for the unambiguous molecular identification of the ambrosia beetle, Xyleborinus saxesenii (Ratzeburg, 1837) (Coleoptera Curculionidae Scolytinae), the cosmopolitan fruit‐tree pinhole borer, widely distributed in temperate regions of the five continents, where it infests a wide range of hardwoods and softwoods. The test was based on real‐time PCR with TaqMan probe technology and was developed on whole insect bodies (adults) as well as on frass produced by the beetle. The test was shown to meet the criteria established by EPPO for the harmonization of molecular diagnostic methods. In particular, the test gave good results in terms of analytical specificity (inclusivity and exclusivity) and analytical sensitivity, and was fully repeatable and reproducible. Since X. saxesenii is one of the most commonly intercepted ambrosia beetles during phytosanitary controls worldwide, this practical diagnostic tool will be useful for its rapid identification of the beetle in biological material (frass, body fragments). The test can be useful in countries where X. saxesenii is a quarantine species, as well as in the EPPO region.

Comparing the succession of microbial communities throughout development in field and laboratory nests of the ambrosia beetle Xyleborinus saxesenii.

Some fungus-farming ambrosia beetles rely on multiple nutritional cultivars (Ascomycota: Ophiostomatales and/or yeasts) that seem to change in relative abundance over time. The succession of these fungi could benefit beetle hosts by optimal consumption of the substrate and extended longevity of the nest. However, abundances of fungal cultivars and other symbionts are poorly known and their culture-independent quantification over development has been studied in only a single species. Here, for the first time, we compared the diversity and succession of both fungal and bacterial communities of fungus gardens in the fruit-tree pinhole borer, Xyleborinus saxesenii, from field and laboratory nests over time. By amplicon sequencing of probed fungus gardens of both nest types at three development phases we showed an extreme reduction of diversity in both bacterial and fungal symbionts in laboratory nests. Furthermore, we observed a general transition from nutritional to non-beneficial fungal symbionts during beetle development. While one known nutritional mutualist, Raffaelea canadensis, was occurring more or less stable over time, the second mutualist R. sulphurea was dominating young nests and decreased in abundance at the expense of other secondary fungi. The quicker the succession proceeded, the slower offspring beetles developed, suggesting a negative role of these secondary symbionts. Finally, we found signs of transgenerational costs of late dispersal for daughters, possibly as early dispersers transmitted and started their own nests with less of the non-beneficial taxa. Future studies should focus on the functional roles of the few bacterial taxa that were present in both field and laboratory nests.

Colonization of oak stumps by the oak pinhole borer in temperate forests and the efficacy of pheromone traps: Implications for pest management

IntroductionThe present changes in climate and land use have led to an increase in pest population densities. The oak pinhole borer, Platypus cylindrus, is one of the ambrosia beetles, which are known to infect wood tissue with fungi from their mycangia. These fungi are responsible for cellulose degradation. This species is now responsible for more frequent timber damage throughout Europe. Therefore, it is assumed that there is a high risk of P. cylindrus outbreaks in the future with possible subsequent oak diebacks. We focused on (1) the influence of stump diameter on P. cylindrus attraction and abundance; (2) the trapping efficacy by a specific pheromone and the impact on nontarget arthropods; and (3) interannual changes in trap catches.MethodsThe research was performed from 2015–2017 with a postharvest survey of stumps. We further analyzed the catches of P. cylindrus and of nontarget arthropods on pheromone traps compared to ethanol-baited traps.Results and discussionIn total, 12,504 adults were trapped during the 3 years of the study. P. cylindrus abundance was positively correlated with stump diameter and interannual changes. The type of compound used for trapping positively affected the trapping efficacy. However, the pheromone type did not have an impact on nontarget beetles. We consider oak stumps to be a reservoir the oak pinhole borer. Therefore, we recommend their debarking or removal, especially in the case of stumps with a larger diameter (over 61 cm).

First experimental evidence for active farming in ambrosia beetles and strong heredity of garden microbiomes.

Fungal cultivation is a defining feature for advanced agriculture in fungus-farming ants and termites. In a third supposedly fungus-farming group, wood-colonizing ambrosia beetles, an experimental proof for the effectiveness of beetle activity for selective promotion of their food fungi over others is lacking and farming has only been assumed based on observations of social and hygienic behaviours. Here, we experimentally removed mothers and their offspring from young nests of the fruit-tree pinhole borer, Xyleborinus saxesenii. By amplicon sequencing of bacterial and fungal communities of nests with and without beetles we could show that beetles are indeed able to actively shift symbiont communities. Although being consumed, the Raffaelea food fungi were more abundant when beetles were present while a weed fungus (Chaetomium sp.) as well as overall bacterial diversity were reduced in comparison to nests without beetles. Core symbiont communities were generally of low diversity and there were strong signs for vertical transmission not only for the cultivars, but also for secondary symbionts. Our findings verify the existence of active farming, even though the exact mechanisms underlying the selective promotion and/or suppression of symbionts need further investigation.

New qPCR protocol to detect Diplodia corticola shows phoretic association with the oak pinhole borer Platypus cylindrus

BACKGROUNDBotryosphaeria canker (causal agent: Diplodia corticola) is considered one of the most important diseases of cork oak (Quercus suber) stands since it necrotizes the subero‐phellodermic layer preventing cork regeneration after harvesting. One of the most intriguing etiological issues of this disease is its plausible spreading through trunk borer insects. In this study, we highlight the phoretic relationship between D. corticola and the oak pinhole borer Platypus cylindrus (Coleoptera, Curculionidae) which massively colonizes debarked cork oaks in southern Europe. We extracted DNA from 154 adults of P. cylindrus collected in six cork oak stands in north‐eastern Spain during the summer of 2021. We developed a new nested quantitative PCR‐based protocol for quick detection of D. corticola carried by insects.RESULTSThe use of real time amplification of a highly specific mitochondrial marker allowed us to detect spore loads down to a single conidium within the first 29 cycles of qPCR. The 29.62% of insect pools (corresponding to 31.16% of studied insects) resulted in an estimated spore load higher than one conidium/insect, with a moderate value of mean spore load for the whole dataset (~33 conidia/insect). Estimated spore load was significantly higher in May and August, regardless of insect abundance in the field.CONCLUSIONThis study provides new tools for diagnosis of this emergent pathogen that would be useful for developing monitoring strategies and epidemiological studies. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Pest categorisation of Platypus apicalis.

The EFSA Panel on Plant Health performed a pest categorisation of Platypus apicalis (Coleoptera: Curculionidae: Platypodinae), an ambrosia beetle, also known as a pinhole borer, for the EU territory. P. apicalis is a polyphagous pest native to New Zealand. The majority of its life cycle is spent inside tree wood, but it does not directly feed on plant tissue, instead larvae and adults feed on a symbiotic fungus (Sporothrix nothofagi which is pathogenic to Nothofagus spp.) vectored by adults and introduced when they bore tunnels into the host. P. apicalis feeds within a wide range of live, often stressed trees, in dead or dying hardwood and softwood trees, and fallen or felled trees. Successful reproduction can occur inside a number of living tree species including Castanea sativa, Pinus spp. and Ulmus spp. P. apicalis is not known to have established outside of New Zealand although findings have been reported in Australia. Whilst there are no records of interceptions of this species in the EU, platypodines are intercepted with solid wood packing material (SWPM) and Platypus species, but not P. apicalis, have been intercepted with wooden logs in Japan. Host plants for planting also provide a potential pathway. Hosts are grown widely across the EU in areas with climates comparable to those in New Zealand where the pest occurs suggesting that conditions in the EU are suitable for its establishment. If introduced into the EU, adults could disperse naturally by flight, perhaps tens or hundreds of metres. The movement of infested wood and host plants for planting within the EU could facilitate spread. Economic impacts in forestry and timber industries would result from the galleries created by P. apicalis and from wood staining caused by the symbiotic fungus. Phytosanitary measures are available to inhibit the entry of P. apicalis. P. apicalis satisfies the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Microclimatic conditions drive summer flight phenology of Platypus cylindrus in managed cork oak stands

AbstractThe oak pinhole borer, Platypus cylindrus F., mainly colonizes oaks (Quercus sp.), and it is considered among the most serious pests of cork oak (Quercus suber L.). Despite being traditionally considered as a secondary pest in thermophilic oak woodlands, outbreaks seem to be more frequent throughout the Mediterranean Basin thus becoming a growing forest health concern. In the Iberian Peninsula, this insect mainly attacks cork oaks (Q. suber) causing intense stress to mature trees specially after cork harvesting season. In this study, we investigated the summer flight phenology of P. cylindrus in six stands located in north‐eastern Spain. We recorded the number of insects trapped in pheromone‐baited traps from late April to early September of 2021, and computed sex ratio, average date of flight and season flight curve in each plot. We fitted a GAM model to evaluate how population dynamics are driven by date and climatic factors. A total of 1795 insects were collected during the sampling period. Population peaks occurred from late May to mid‐August. The fitted GAM predicted changes in the number of captures throughout the summer varying with microclimatic conditions. In addition, diversity of trapped non‐target Curculionidae resulted moderate with low evenness including either ambrosia or bark beetles. This study represents the first attempt at modelling P. cylindrus flight, thus providing insights into the association between climate, pests and forestry.

First report of the pinhole borer (Euplatypus sp.) to cause stem bleeding of rubber trees in the Philippines

First report of the pinhole borer (Euplatypus sp.) to cause stem bleeding of rubber trees in the Philippines

Rare European Beetle Treptoplatypus oxyurus (Coleoptera: Platypodidae) in Managed Uneven-Aged Forests of Croatia

Bark beetle outbreak sites were analysed before sanitary logging in Gorski Kotar County during spring, summer and autumn 2021. Downed European silver fir trees were inspected for red-listed saproxylic entomofauna. Among other species, the fir pinhole borer (Treptoplatypus oxyurus, Dufour, 1843) (Coleoptera: Platypodidae) was observed and studied on-site and in the laboratory. Symptoms of T. oxyurus presence were recognised as white filamentous bites of sawdust on the bark of the fir trees and the surrounding soil. Every tree infested infested with T. oxyurus was measured (diameter at breast height, height/length), and its position was recorded. Segments were collected for laboratory analysis to evaluate the layout and position of T. oxyurus gallery system. The results showed that individual corridors of T. oxyurus, as a rule, never intersect, cross or connect. Each family of beetles (male, female and their offspring) lives separately in its corridor system. There were examples of corridors that were very close to each other but did not touch. T. oxyurus is still completely unknown to forest operatives in Croatia, who do not recognise symptoms of its occurrence.

Bacterial community associated with the ambrosia beetle Platypus cylindrus on declining Quercus suber trees in the Alentejo region of Portugal

AbstractIn Portugal, the oak pinhole borer Platypus cylindrus and its mycobiota have been associated with cork oak (Quercus suber) death, but no knowledge exists regarding the associated bacterial community. However, it is known that some bacteria are important for ambrosia beetle symbiosis and play a role in oak tree health. To explore the bacteria associated with this beetle and its host, with the ultimate goal of highlighting potential roles in oak decline, this study used a culture‐dependent approach for strain isolation and phylogenetic identification using 16S rRNA gene sequencing and multilocus sequence analysis (MLSA). The bored galleries of different cork oak trees from a cork stand in Alentejo, together with the body and mycangia of adult beetles, were investigated. The samples revealed a diverse community comprising 500 isolates with 64 distinct types of bacterial colonies. Sixty‐eight strains were selected for sequencing and used for phylogenetic analysis, 40 from wood galleries and 28 from beetles. Thirty‐two genera of bacteria were identified, 18 of which were described for the first time within oak–beetle interactions. Major taxonomic groups were Actinobacteria in beetles and Enterobacterales in wood galleries. Although specific oak bacterial pathogens were not detected, a group of distinct strains detected in wood galleries, potentially belonging to a new Pectobacteriaceae species, were able to produce mild symptoms on cork oak plantlets. This study reports for the first time the biodiversity of culturable bacteria associated with the Q. suber–P. cylindrus interaction, their relevance to both organisms and the possible contribution to oak decline.

Raffaelea quercina sp. nov. Associated with Cork Oak (Quercus suber L.) Decline in Portugal

Research Highlights: Raffaelea quercina sp. nov. is an ophiostomatoid fungus isolated from the ambrosia beetle Platypus cylindrus. The species occurs in symptomatic Portuguese cork oak trees, (Quercus suber L.), exhibiting vegetative decline. Background and Objectives: Quercus suber L. is a species restricted to the Mediterranean basin, of special economic importance as it constitutes the crucial raw material for the cork production industry, in particular for Portugal, the world’s leading producer. Over the last three decades a progressive and alarming decline of cork oak trees has been observed across its distribution area, including Portugal. The ambrosia beetle Platypus cylindrus, commonly known as the oak pinhole borer, establishes symbiotic relationships with fungi from which it depends for survival and for oak colonization. Some of these fungi are ophiostomatoid species of the Raffaelea genus, known as ambrosia fungi associated with ambrosia beetles. Some Raffaelea species exhibit phytopathogenic activity causing wilting and/or death of trees. The objective of the present study is to identify the association between P. cylindrus and Raffaelea species in Portuguese cork oak stands showing symptoms of disease and decline. Materials and Methods: A total of 300 adult insects were collected as they emerged from cork oak logs, sampled from symptomatic trees. Axenic isolates of Raffaelea species were obtained from the beetles and their galleries in the trunks and identified based on morphological features and molecular analysis of the SSU and LSU rDNA regions. Results: Two Raffaelea species were identified, i.e., R. montetyi and a novel Raffaelea species closely related to R. canadensis. The novel species is morphologically and genetically characterized in this study, and erected as Raffaelea quercina M.L. Inácio, E. Sousa & F. Nóbrega, sp. nov. Raffaelea quercina constitutes a new phytopathogenic fungal species associated with P. cylindrus and cork oak trees exhibiting symptoms of vegetative decline. Conclusions: Raffaelea species appear to have a significant role in cork oak decline. Future research on the association between P. cylindrus and Raffaelea species, encompassing the trans-European and North African wide-range of cork oak stands, would further clarify the relationships between ambrosia beetles, associated fungi and cork oak decline, contributing to a better understanding of the phenomena and for strategies aiming to halt the continuous decline of the unique cork oak stands enclosed in the Mediterranean basin.

Differential flight responses of two ambrosia beetles to ethanol as indicators of invasion biology: the case with Kuroshio shot hole borer (Euwallacea kuroshio) and fruit‐tree pinhole borer (Xyleborinus saxesenii)

1. Host selection and utilization by ambrosia beetles ranges from healthy trees to weakened, dying, or dead trees. Compared to weakened trees, healthy trees emit little to no ethanol, which is stress‐induced and a by‐product of anaerobic respiration. The current study tested the attraction of two invasive ambrosia beetles, Kuroshio shot hole borer (KSHB), one member of the species complex, Euwallacea nr. fornicatus, and fruit‐tree pinhole borer, Xyleborinus saxesenii, to four treatments with or without ethanol.2. GC–MS analyses confirmed the release of ethanol from the ethanol lure and boxelder log filled with ethanol and not from the other two treatments. Kuroshio shot hole borer was not preferentially attracted to any ethanol treatment, whereas X. saxesenii responded positively to the ethanol treatments. The boxelder bolt infused with ethanol was the most attractive treatment to X. saxesenii.3. We propose that the differential behavioural responses of these two ambrosia beetles to ethanol correspond to their differential aggressiveness for attacking healthy trees: KSHB attacks healthy trees, whereas X. saxesenii attacks weakened trees. The proposal is further substantiated by a literature survey on bark and ambrosia beetles from Scolytinae. The survey also indicates that the majority of bark and ambrosia beetles from Scolytinae respond positively to ethanol.4. Although ethanol is widely used and is an effective lure for attraction of many bark and ambrosia beetles, findings from this current study and many others necessitate research and development of alternative lures for more aggressive species which are ecologically and economically more devastating.

On the horns of a dilemma: toward a better understanding of the Monacon species (Hymenoptera: Perilampidae) of Borneo

ABSTRACT A new species of Monacon is described from Borneo based on digital images, COI sequences and X-ray microtomography. The natural history of this primary parasitoid is documented and its host, a pinhole borer or ambrosia beetle, is documented with digital images and a COI sequence. The X-ray microtomography revealed that the frontal horn that is characteristic of the genus Monacon is not simply a cuticular process, but is associated with tissues, and may have a sensory function.

Host selection behavior mediated by differential landing rates of the walnut twig beetle, Pityophthorus juglandis, and associated subcortical insect species, on two western North American walnut species, Juglans californica and J. major

AbstractThe walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), vectors a phytopathogenic fungus, Geosmithia morbida Kolařík et al. (Hypocreales), which causes thousand cankers disease (TCD) in walnut (Juglans sp.) and wingnut (Pterocarya sp., both Juglandaceae) trees. We investigated an early point in disease inception in two walnut species – Juglans californica S. Wats. and Juglans major (Torr. ex Sitsgr.) Heller – native to riparian forests of the western USA by comparing P. juglandis flight and landing responses to small‐diameter branch sections. Twenty unbaited branch sections (10 each of J. californica and J. major) were presented in a completely randomized design to populations of P. juglandis at the USDA Agricultural Research Service, National Clonal Germplasm Repository (NCGR) Juglans collection located at Wolfskill Experimental Orchards (Winters, CA, USA) and at the California State University, Chico, Agricultural Teaching and Research Center (ATRC, Chico, CA). These assays were carried out within a 4‐ to 6‐year period when weekly flight surveys with aggregation pheromone‐baited multiple funnel traps revealed that P. juglandis flight activity–abundance was higher at the NCGR than at the ATRC. For the landing rate assays, adhesive‐coated acetate sheets were wrapped around the branch sections and exchanged weekly. Three assays were completed at the NCGR (assays 1–3), whereas one assay was completed at the ATRC (assay 4). Landing rates on these traps were compared between J. californica and J. major. Two additional assays (5 and 6) were completed at the NCGR to compare responses to branch sections of J. californica and to similarly sized cardboard tubes (negative control). All six assays were completed over a 4‐year span during the 4‐ to 6‐year weekly flight survey period. Pooled landing rates of male and female P. juglandis (assays 1–4) demonstrated a preference by both sexes for J. californica over J. major. In assay 5 there was no preference by males or females for J. californica over the negative control, perhaps due to the low flight activity–abundance of P. juglandis during the assay. When repeated at a time of higher flight activity–abundance (assay 6), male and female landing rates on J. californica exceeded those on the negative control. Females of the invasive fruit‐tree pinhole borer (an ambrosia beetle), Xyleborinus saxeseni (Ratzeburg), and an invasive bark beetle, Hypothenemus eruditus Westwood (both Coleoptera: Scolytidae), showed relatively higher flight responses than either sex of P. juglandis during most assays, suggesting higher population densities of these two other invasive species at the two orchards or a greater sensitivity to host volatiles. Xyleborinus saxeseni and H. eruditus preferred to land on J. major over J. californica and on J. californica over the negative control. Similarly, an invasive longhorned beetle, Nathrius brevipennis (Mulsant) (Coleoptera: Cerambycidae), showed a significant preference for J. major over J. californica, but not for J. californica over the negative control. More male N. brevipennis were trapped than females at both study sites [sex ratio ranged from 5:1 (assay 6) to 39:1 (assay 4)], and flight occurred only in the spring and early summer months. Another ambrosia beetle trapped at the NCGR and ATRC, Xyleborus affinis Eichhoff, represented the first records of this species from western North America. In summary, flight responses recorded in some of our assays for P. juglandis and several other subcortical insects on Juglans indicate that host preference by these insects may be determined by long‐range olfactory cues that do not involve pheromones.

First report of the invasive South American pinhole borer Euplatypus paralellus (F) (Coleoptera: Curculionidae: Platypodinae) on arecanut

The invasive South American pinhole borer Euplatypus paralellus (F) is reported for the first time on arecanut palms from Kasaragod, Kerala, India.

A new species of Diapus Chapuis from South-West China and North Thailand (Coleoptera: Curculionidae: Platypodinae).

The genus Diapus Chapuis was erected (Chapuis 1865) for four species of pinhole borer (Curculionidae: Platypodinae) from the Oriental region and New Guinea. It was distinguished from other platypodine genera primarily by the widely separated procoxae (Chapuis 1865). Hopkins (1914) designated Diapus quadrispinatus Chapuis, 1865 as the type species of the genus. The genus is currently placed in the platypodine tribe Tesserocerini, subtribe Diapodina (Alonso-Zarazaga & Lyal 2009). Only two genera are included in the Diapodina, Diapus and Genyocerus Motschulsky (Alonso-Zarazaga & Lyal 2009, Jordal 2015). Diapus is distinguished from Genyocerus by the following characters (Wood 1993, Beaver & Liu 2007): 1. In Diapus, the scutellum is narrower and more sunken, not flush with the elytral surface posteriorly as it is in Genyocerus. 2. The mycangial pores of Diapus are sometimes fused to form a transverse or crescentic bar on each side of the midline of the pronotum. This does not occur in Genyocerus. 3. The antennal club of Diapus sometimes has a median testaceous strip lacking sensillae on the anterior face. This strip is never present in Genyocerus. 4. The males of Diapus never possess a membranous extension of the apical margin of the fourth abdominal ventrite, present in some species of Genyocerus. 5. The females of Diapus often bear deciduous mandibular appendages, which are never present in Genyocerus (Beaver & Liu 2007).

Fine structure and functional comments of mouthparts in Platypus cylindrus (Col., Curculionidae: Platypodinae)

Oak pinhole borer, Platypus cylindrus is seen in recent years as one of the biggest enemies directly involved in the observed decline of cork oak in Mediterranean forests with all the economic implications. As an ambrosia beetle, it has developed its effective drilling mouthpart enough to make tunnels in hardwood of the tree. The fine structural aspects of the mouthpart using the field emission scanning electron microscopy are analyzed about 23 adults collected in galleries of infested cork oak trees (Quercus suber) in a littoral forest of northwest Algeria. These adults are preserved in alcohol 70%, cleaned and coated with gold. The mouthparts of this beetle consist commonly of a labrum, a pair of mandibles, a pair of maxillae and the labium but with adapted structure to excavate galleries in the hardwood. In this role is also involved the first pair of legs. The function that present the different structures related to the construction of the tunnels is discussed. Both of maxillary and labial palpi direct the food to the mouth and hold it while the mandibles chew the food. The distal ends of these palpi are flattened and have shovel-like setae. Females have larger maxillary palpi than males and this is related to the particular biology of each sex.