Morphology of the mouthparts of the spittlebug Philagra albinotata Uhler (Hemiptera: Cercopoidea: Aphrophoridae)

Mouthparts associated with feeding behavior and feeding habits are important sensory and feeding structures in insects. To obtain a better understanding of feeding in Cercopoidea, the morphology of mouthparts of the spittlebug, Philagra albinotata Uhler was examined using scanning electron microscopy. The mouthparts of P. albinotata are of the typical piercing–sucking type found in Hemiptera, comprising a cone-shaped labrum, a tube-like, three-segmented labium with a deep groove on the anterior side, and a stylet fascicle consisting of two mandibular and two maxillary stylets. The mandibles consist of a dorsal smooth region and a ventral serrate region near the apical half of the external convex region, and bear five nodules or teeth on the dorsal external convex region on the distal extremity; these are regarded as unique features that distinguish spittlebugs from other groups of Hemiptera. The externally smooth maxillary stylets, interlocked to form a larger food canal and a smaller salivary canal, are asymmetrical only in the internal position of longitudinal carinae and grooves. One dendritic canal is found in each maxilla and one in each mandible. Two types of sensilla trichodea, three types of sensilla basiconica and groups of multi-peg structures occur in different locations on the labium, specifically the labial tip with two lateral lobes divided into anterior sensory fields with ten small peg sensilla arranged in a 5 + 4 + 1 pattern and one big peg sensillum, and posterior sensory fields with four sensilla trichodea. Compared with those of previously studied Auchenorrhyncha, the mouthparts of P. albinotata may be distinguished by the shape of the mandibles, the multi-peg structures and a tooth between the salivary canal and the food canal on the extreme end of the stylets. The mouthpart morphology is illustrated using scanning electron micrographs, and the taxonomic and putative functional significance of the different structures is briefly discussed.     

Anterior alimentary canal of the pear Psylla,Psylla pyricola foerster (Homoptera,Psyllidae)

Scanning and light microscopy investigations of the anterior alimentary canal of the pear psylla, Psylla pyricola Foerster (Homoptera: Psyllidae), revealed the morphology of the labium and stylets, as well as the presence of sensory structures and a valve in the precibarium. The labium consists of three telescoping segments with an internal labial groove, which surrounds and supports the stylet bundle. Also a part of the labial groove is the internal labial clamp. The stylet bundle is comprised of paired styliform mandibles and maxillae, which interlock to form the food and salivary canals. The stylet bundle proximal to the labium forms a large loop within a membranous crumena. When fully retracted the coiled stylets are under tension. Stylet extension generates increasing tension so that when retracted the stylets readily recoil within the crumena. Penetration of leaf tissues by the stylet bundle is dependent on the interaction between stylet muscles, opening and closing of the labial clamp, the barbed stylet tips, and the ventral position of the labium. Proximal to the crumena the paired stylets separate and diverge at the entrance of the precibarium, which is formed by the interlocking of the epi-and hypopharynges. There are 18 sensory structures in the precibarium, as well as a precibarial valve. These structures appear to be homologous to similar structures observed previously in aphids and leafhoppers. The morphology and the location of the precibarial sensilla suggest that, like the precibarial sensory organs of aphids and leafhoppers, they are gustatory and probably mediate acceptance or rejection of plant fluids, thus playing a major role in locating tissues for feeding.     

Opening mechanism of the mouth of the hematophagous hemipteran, Triatoma infestans

A morphological study of the tips of the stylets in an haematophagous hemipteran has been performed with a scanning microscope in order to determine both the relative positions of the mouthparts during a meal, and the means by which the ‘functional mouth’ can open. If the stylets of Triatoma are examined following severance of the labium, differences in the morphology and relative position of the two maxillary tips are observed. When, prior to a meal, the insect explores the medium with its mouthparts, the tips of its maxillary stylet are united. By contrast, when the bug is pumping food the left stylet is retracted relative to the right stylet and its tip is bent outwards.We have studied the mechanics of the system which allows the tip of the left maxillary to rock, resulting in the opening of the alimentary canal. Finally, we have re-examined the stylet movements of dissected animals in the light of these new morphological findings.     

Ultrastructure of the mouthparts of adult sweetpotato whitefly,Bemisia tabaci Gennadius (Homoptera: Aleyrodidae)

The fine structure of the mouthparts of the whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), was examined by scanning and transmission electron microscopy. Adult whitefly mouthparts are similar to those of other homopterans, especially aphids, being composed of the labrum, the labium, and the stylets. The stylet bundle is the feeding organ of the whitefly and is composed of 2 mandibular stylets and 2 maxillary stylets. Mandibular stylets, which are located on the outer aspect of the stylet bundle, each contain 2 dendrites. The tips of the mandibular stylets are curved inward, and there are barb-like ridges on the lateral aspects, which probably function in piercing and cutting plant tissues and in anchoring the stylets in the tissues. The maxillary stylets are not innervated and are interlocked to form 2 separate compartments, the food canal and salivary canal. At the distal end of the interlocked maxillary stylets, there is a small depression, which may allow for mixing of the salivary canal and food canal components. Movement of the B. tabaci stylets during feeding is discussed in comparison with other homopterans.     

Oviposition behaviour in Lygus rugulipennis: a morpho-functional study

Before oviposition, a Lygus rugulipennis (Poppius) (Heteroptera: Miridae) female explores the substrate with her mouthparts, performing ‘probing’ behaviour which eventually leads to a choice of oviposition site. In this study, morphological and behavioural observations were carried out in order to define the mechanisms through which female bugs recognise suitable oviposition sites. The morphological study was conducted using electron‐microscopy techniques, while the behavioural experiments aimed at the temporary (using ZnSO₄) or permanent (i.e., cauterization of the rostrum and ablation of both stylets and labium) inactivation of sensory structures located in the labium tip and in the stylets, which are probably involved in oviposition site selection. The tip of the labium of L. rugulipennis females is characterised by the presence of 11–12 uniporous gustatory sensilla which are innervated by 3–6 sensory neurones. One aporous mechanoreceptor is located ventrally on both areas of the labium tip. Other aporous mechanosensilla are found more proximally on the labium. ZnSO₄ labium tip treatment did not affect oviposition site selection, while stylet amputations, as well as rostrum cauterisations, resulted in almost complete oviposition failure. Labium tip‐ablated females oviposited similarly to control females. These results suggest that the sensory neurones associated with the stylets are involved in the location of the oviposition site. Uniporous gustatory sensilla on the labium tip are not involved in the final steps of the oviposition behaviour. However, they seem to play a role in assessing the suitability of the substrate as a food source.     

Fine structure and sensory apparatus of the mouthparts of the pear psyllid,Cacopsylla chinensis (Yang et Li) (Hemiptera: Psyllidae)

The pear psyllid, Cacopsylla chinensis (Yang et Li) (Hemiptera: Psyllidae), is one of the most significant economic pests of pear in China, causing direct damage through feeding by the highly specialized piercing–sucking mouthparts. The ultrastructural morphology and sensory apparatus of the mouthparts of the adult were examined using scanning and transmission electron microscopy. The piercing–sucking mouthparts of C. chinensis are composed of a three-segmented labium with a deep groove in the anterior side, a stylet fascicle consisting of two mandibular and two maxillary stylets, and a pyramid-shaped labrum. Proximal to the labium, the stylet fascicle forms a large loop within a membranous crumena. Mandibles, with more than ten teeth on the external convex region, can be seen on the distal extremity. Smooth maxillary stylets are interlocked to form a larger food canal and a smaller salivary canal. One dendritic canal housing 2 dendrites is also found in each mandible. Two types of sensilla trichodea, four types of sensilla basiconica, single as well as groups of sensilla campaniformia, and oval flattened sensilla occur in different locations on the labium, whereas a kind of sensilla basiconica is at the junction of the labrum and anteclypeus. Sensilla trichodea and sensilla campaniformia, always present with denticles, are present on the middle labial segment. Three types of sensilla basiconica, two types of sensilla trichodea and two oval flattened sensilla are located on the distal labial segment. The mouthpart morphology and abundance of sensilla located on the labium in C. chinensis are illustrated, along with a brief discussion of their taxonomic and putative functional significance.     

Sensory innervation monitoring movement and position in the mandibular stylets of the aphid, Brevicoryne brassicae

The sensory innervation of the mandibular stylets of the aphid Brevicoryne brassicae (L.) has been examined by electron microscopy. Two groups of sensory neurones are present in the mandible. Each has two neurones, one with a short dendrite extending into the base of the mandible and ending in the base and another with a long microtubular process which extends 500 m? down to the distal tip of the mandible. The two neurones are enclosed by an ensheathing cell comparable to the trichogen cell enveloping the group of neurones innervating pegs and hairs. This ensheathing cell is supported by extensive electron-dense filaments to form a scolopale and is embedded in the mass of stylet-forming cells at the base of the mandible. The inner segments of the dendrites are anchored to the ensheathing cell by desmosome junctions. Desmosome junctions also bind the microtubular outer segments of the short and long dendrite to each other. There is no evidence of a dendritic sheath enclosing the distal portion of the short dendrite which ends while still in the extracellular space within the ensheathing cell. The microtubular process of the long dendrite extends down the lumen of the mandible enclosed by a close-fitting extracellular sheath which penetrates and is attached to the cuticular wall of the mandible tip. Distally this sheath is thickened on one side. Deflection of the mandible would therefore deform the dendritic membrane asymmetrically because the thin walls of the sheath would bend more than the thick walls. This would exert an unequal mechanical strain on the dendritic membrane which could result in depolarization in response to deflection in a particular direction. The arrangement of the dendrites and their sheaths within the mandible is such that deflection to the right would distort one dendrite in the same way as deflection to the left would distort the other.     

Morphology of the sweet potato whitefly,Bemisia tabaci (Homoptera,Aleyrodidae) relative to virus transmission

 The stylet bundle of the sweet potato whitefly, Bemesia tabaci, consists of paired mandibles and maxillae. The latter interlock to form the food and salivary canals. Its salivary system consists of paired primary and accessary glands in the thorax. Primary and accessory gland ducts on each side of the nerve cord fuse to form lateral ducts that course anteroventrally to the midline and continue in parallel down the hypopharynx to eventually fuse to form the single afferent duct of the salivary pump. Saliva exiting the pump via the efferent duct enters the salivary canal of the maxillae. Food from the maxillary food canal passes from the antecibarium to the postcibarium or sucking pump and, per os, to the pharynx and esophagus of the foregut. The esophagus extends from the head to the base of the abdomen where it and the anterior midgut intimately mingle with the anterior hindgut to form a filter chamber. The midgut then proceeds dorsocaudally before looping anteroventrally to join the hindgut. The latter gives off two fingerlike Malpighian tubules before entering the filter chamber, whence it proceeds dorsocaudally to the anus within the vasiform orifice. Where possible, the morphology of Bemisia is discussed in relation to plant virus transmission and the morphologies of more thoroughly studied homopteran vectors such as aphids and leafhoppers. Accepted: 9 July 1996     

Morphological description of the mouthparts of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae)

Scanning (SEM) and transmission (TEM) electron microscopy were used to elucidate the morphology of the rostrum, as well as the mandibular and maxillary stylets of the psyllid Diaphorina citri, vector of phloem-inhabiting bacteria associated with citrus huanglongbing (HLB) disease. D. citri has a cone-shaped rostrum that extends behind the pair of prothoracic coxae. The stylet bundle comprises a pair of mandibular (Md) and maxillary (Mx) stylets with a mean length of 513.3 μm; when retracted, their proximal portions form a loop and are stored in the crumena (Cr). Serial cross-sections of the rostrum revealed that the mandibles are always projected in front of the maxillary stylets. The two maxillary stylets form the food and salivary canals, with diameters of 0.9 μm and 0.4 μm respectively. These two canals merge at the end of the stylets forming a common duct with a length of 4.3 μm and a mean diameter of 0.9 μm. The acrostyle, a distinct anatomical structure present in the common duct of aphid maxillary stylets, was not observed by TEM in the ultrathin cross-sections of the common duct (CD) of D. citri. This study provides new information on D. citri mouthparts that may help to understand the feeding behaviour of this important vector of HLB-associated bacteria.     

An investigation of preferential feeding habit in fourAsclepiadaceae by the Aphid,Aphis nerii B. de F.

Summary Penetration of the stems ofAraujia sericofera, Asclepias curassavica, Cynanchum ellipticum andSarcostemma viminale by stylets of the aphidAphis nerii was studied with light and differential interference contrast microscopes. Of a total of 118 stylets and 446 stylet tracks observed in cross-sections of stems of the fourAsclepiadaceae, 97 stylets and 372 stylet tracks terminated within the internal primary phloem. Of the remainder, 15 stylets and 74 tracks terminated within the external primary phloem. 22 stylets and 179 of the stylet tracks penetrated the external phloem on the way to the internal phloem. Of these, only four stylets and 32 of the stylet tracks showed signs of attempted probes of the external phloem. It is suggested thatAphis nerii may obtain not only its essential food requirements but also cardiac glycosides as a basis for chemical aposematism.     

Ultrastructure of the copulatory stylet and accessory spines in Haplopharynx quadristimulus (Turbellaria)

The copulatory organ of Haplopharynx quadristimulus Ax, 1971 (Carolina form, Rieger, 1977) consists of a proximal prostatic vesicle and a distal stylet apparatus comprising a central tubular stylet and four to five peripheral accessory spines. By electron microscopy it could be seen that the stylet and spines were intracellular specializations. The copulatory organ can be interpreted as a specialization of an epithelial canal extending from the testes to the body wall. In the complex stylet apparatus, the epithelium was differentiated into six cell types. The stylet, which was formed in a matrix syncytium next to the prostatic vesicle, extended into the lumen of the stylet canal. The interior of the stylet apparatus contained one group of cells that had thick ciliary rootlets and another that had rootlet-like ribbons.The cells that contain the rootlets enveloped bundles of longitudinally arranged muscles. The accessory spines were formed in cells which lay peripheral to the muscle bundles. The spines, stylet, rootlet-like ribbons, and rootlets had similar patterns of periodic cross striations. The similarity in striation patterns suggests that the accessory spines and stylet are composed of modified ciliary rootlets.     

The “acrostyle”: A newly described anatomical structure in aphid stylets

The recent demonstration that a plant virus could be retained on protein receptors located exclusively in a small area inside the common duct at the tip of aphid maxillary stylets indicated the possible existence of a distinct anatomical structure at this level. Since no distinct feature within the common duct of any aphid species has ever been reported in the literature, we first carefully re-examined the distal extremity of the maxillary stylets of Acyrthosiphon pisum using transmission- and scanning-electron microscopy. Here, we describe an area of the cuticle surface displaying a different structure that is limited to a “band” paving the bottom of the common duct in each opposing maxillary stylet. This band starts at the very distal extremity, adopts a “comma-like” shape as it continues up towards the salivary canal, reducing in width and disappearing before actually reaching it. Investigations on several aphid species led to the conclusion that this anatomical feature—which we have tentatively named the “acrostyle”—is highly conserved among aphids. We then produced an antibody recognizing a consensus peptide located in the middle of the RR-2 motif of cuticular proteins from A. pisum and showed that this motif is accessible specifically within the acrostyle, indicating a higher concentration of cuticular proteins. While it is clear that at least some viruses can use the acrostyle to interact with their aphid vectors to ensure plant-to-plant transmission, the role of this new “organ” in aphid biology is unknown and calls for further investigation in the near future.     

The Stylet Apparatus of Monostiliferous Hoplonemerteans

This paper compares the ultrastructure, development, and functionalmorphology of the stylet apparatus in monostiliferous hoplonemerteans(Phylum Nemertea: Class Enopla). The apparatus occurs in themiddle region of the worm's eversible proboscis and consistsof two main components: 1) a central stylet that is attachedto an anchoring device called the basis; and 2) reserve styletsacs that contain nail-like reserve stylets. The knob-shapedproximal piece of the central stylet is embedded in the anteriorend of the basis, and the tapered shaft of the stylet is directedanteriorly. When the proboscis is fully everted, the centralstylet is used to stab such prey as polychaete worms and smallcrustaceans. Wounds inflicted by the stylet allow the introductionof paralytic neurotoxins that are produced by glandular cellsin the epithelial lining of the proboscis. Reservestylets formintracellularly within the reserve stylet sacs and serve toreplace the central stylet when it becomes lost or damaged.Fully developed stylets typically measure 50 to 250 µmin length and comprise an organic core surrounded by an inorganiccortex that contains calcium phosphate. In juvenile worms thatare four days to several weeks old, reserve stylets are assembledbefore other components of the stylet apparatus are fully differentiated.Subsequently, a reserve stylet is transferred to the centralregion of the proboscis and placed on the basis. Stages in theprocess of stylet attachment are described, and the probablesequence by which the stylet apparatus co-evolved with toxin-producingcells is discussed.     

Composite,haustellate mouthparts in netwinged beetle and firefly larvae (Coleoptera,Cantharoidea: Lycidae,Lampyridae)

During lycid embryogenesis, labral and mandibular anlagen develop separately. Each anterolateral corner of the labrum elongates into a stylet, while the whole of each mandible involutes into a flute that is open to the lateral aspects. The stylets and flutes interlock in such a way as to leave canals, fashioning left and right haustellate apparatuses. During lampyrid embryogenesis, only one pair of anlagen forms instead of two. The pair matures into sharp, arcuate appendages that appear to be typical mandibles, but nevertheless a canal forms internally. The canal is not formed by coadaptation of two appendages; instead, cells within the pair create the canal autonomously. Indications are that the canal is homologous between these two families. It is suggested that in lampyrids, labral and mandibular cell fields develop together in the same anlage but behave according to their own respective programs, forming the canal with morphogenetic movements that are comparable to those of lycids. © 1994 Wiley-Liss, Inc.     

Anatomy and ultrastructure of the male reproductive system in Pleioplana atomata (Platyhelminthes: Polycladida)

Abstract. The ultrastructure of the male reproductive system in the polyclad flatworm Pleioplana atomata is described. Numerous testes are scattered throughout the entire body but are heavily concentrated on the ventral side. All stages of differentiating sperm cells are present in all testes follicles. Intercellular bridges connect spermatocytes and spermatids derived from a single spermatogonium. In the distal part of spermatids, a zone of differentiation develops with a row of microtubules beneath the plasmalemma. Adjacent to these microtubules, an intercentriolar body is flanked by two basal bodies that give rise to two axonemes (each with a 9+“1” microtubular pattern) that face in opposite directions. The Golgi complex appears in the central portion of the spermatid and produces numerous small and large electron-dense bodies. The small bodies surround the nucleus, whereas the large bodies cluster along with the mitochondria in the central part of the spermatid. Development of the spermatid leads to cell elongation and formation of a filiform, biflagellate mature spermatozoon with cortical microtubules all along the sperm shaft. The male canal system consists of paired vasa deferentia that separately enter a single seminal vesicle. A single prostatic canal connects the seminal vesicle to the prostatic vesicle. Ultrastructurally, the seminal vesicle and prostatic canal are very similar, and along with the prostatic vesicle and stylet pocket, are lined by a ciliated epithelium. The ultrastructure of the prostatic vesicle indicates that it probably produces a large volume of seminal fluid that, along with spermatozoa, is transferred to the mating partner through a stylet. Some of the findings, particularly on sperm ultrastructure, may provide characters useful for phylogenetic analysis.     

Observations on penetration of Barley leaves by the aphidRhopalosiphum maidis (Fitch)

Summary Penetration of leaves of barley,Hordeum vulgare L., by the corn leaf aphid,Rhopalosiphum maidis (Fitch), was studied with light, phase, and electron microscopes. Penetration of epidermis and mesophyll was largely intercellular, that of vascular bundles or veins largely intracellular. Like other aphids,R. maidis secretes a salivary sheath which surrounds the stylets. When mesophyll cells and parenchymatous elements of the veins were penetrated by stylets, their protoplasts were pushed to one side by intruding sheath material; hence, the protoplasts were not punctured by the stylets, although sometimes the plasmalemma of penetrated cells was ruptured by sheath material. The salivary sheaths ended more or less abruptly outside the walls of sieve elements being fed upon, the maxillary stylets projecting beyond the sheaths and into the sieve elements. Before penetrating a functional sieve element the aphid apparently flushes its stylets in order to clear them for ingestion of food. Salivary and food canals merge near the tips of the maxillary stylets to form a single canal, which ends short of the tips.This research was supported by the U.S. National Science Foundation (GB-8330).     

Studies on the tardigrades. I. Fine structure of the anterior foregut of Milnesium tardigradum Doyère

The fine structure of the anterior foregut of the tardigrade Milnesium tardigradum is presented. The oral region consists of a terminal mouth opening surrounded by six plate-like lips lying within a circlet of six prominent papillae. The buccal cavity is enclosed within a thick cuticular tube which possesses appendage structures, the stylet sheaths, stylet supports and paired protrusible stylets. Two large salivary glands envelop the buccal structures and contain voluminous amounts of secretory product. The arrangement, possible functions and phyletic significance of these structures are discussed.     

Ultrastructure of the copulatory organ of Haplopharynx quadristimulus and its phylogenetic significance (Plathelminthes,Haplopharyngida)

Summary The male reproductive system in Haplopharynx quadristimulus consists of paired testes, sperm ducts, seminal vesicles, seminal ducts, a copulatory organ containing prostatic vesicle and stylet apparatus, and the male canal. By electron microscopy all components appeared to be regional specializations of a canal extending from the testes to the body wall and lined by a multiciliated epithelium. The epithelium of the stylet apparatus contained six different cell types. One cell type (matrix syncytium) formed the stylet and the other five were located distal to the stylet/prostatic-vesicle junction along the male system epithelium. Each cell type was attached to the supporting intercellular matrix at a different level along the stylet apparatus. All cell types extended to the distal end of the stylet apparatus regardless of where they originated along its length. The cells in the apparatus lacked cilia, but one of the cell types contained rootlets. Modified rootlets or rootlet derivatives were possibly present in another cell type in the form of rootlet-like ribbons. The findings support the monophyly of the Macrostomida Haplopharyngida (by common occurrence of a matrix syncytium) and at the same time suggest their separation as two distinct taxa (by differences in the structure of the prostatic vesicle and other parts of the stylet apparatus).Abbreviations a accessory spine - c circular muscle - ce centriole - ci cilium - di dictyosome - e epithelial cell - ed ejaculatory duct - ep epidermal cell - f rootlet-like ribbon - g prostatic gland cell neck - g1 type I gland cell granules - g2 type II gland cell granules - g3 type III gland cell granules - h hemidesmosome - i intercellular matrix - im internal muscle - j septate junction - l stylet apparatus lumen - le spine lateral extension - lm longitudinal muscle - m matrix syncytium - mc male-canal epithelial cell - me male canal - mp male pore - mt microtubules - mv microvilli - n nucleus - nc nerve cell body - np nerve process - om oblique muscle - p prostatic vesicle epithelial cell - pv prostatic vesicle - r rootlet - s stylet - sa stylet apparatus - sc sensory receptor - sd sperm duct - se seminal duct - sl stylet lumen - sp spot desmosome - sr sperm - sv seminal vesicle - t terminal web - te testis - u ultrarhabdite - z zonula adhaerens - 2 cell type 2 - 3 cell type 3 - 4 cell type 4 - 6 cell type 6     

Fine structure of the mouthparts of Diostrombus politus and Proutista moesta (Hemiptera: Derbidae)

Insect mouthparts are important sensory and feeding structures, morphological studies of this organ can provide additional data for phylogenetic studies. The planthopper superfamily Fulgoroidea is among the dominant groups of phytophagous insects, however, the mouthparts ultrastructure of this superfamily remains unsatisfactorily studied. This study investigates the ultrastructure of the mouthparts of two species in the family Derbidae (Hemiptera: Fulgoroidea), Diostrombus politus Uhler and Proutista moesta (Westwood), using a scanning electron microscope. The results show that these two derbids are of a typical piercing-sucking type found in Hemiptera. They consist of a cone-shaped labrum, a three-segmented labium and a stylet fascicle with two interlocked maxillary stylets incompletely wrapped by two mandibular stylets. The arrangement of the sensilla on the labial tip differ slightly between the two derbid species, and the subapical labial sensilla are likely different among genera in the family Derbidae.     

Correlation of stylet activities by the glassy-winged sharpshooter, Homalodisca coagulata (Say), with electrical penetration graph (EPG) waveforms

Glassy-winged sharpshooter, Homalodisca coagulata (Say), is an efficient vector of Xylella fastidiosa (Xf), the causal bacterium of Pierce's disease, and leaf scorch in almond and oleander. Acquisition and inoculation of Xf occur sometime during the process of stylet penetration into the plant. That process is most rigorously studied via electrical penetration graph (EPG) monitoring of insect feeding. This study provides part of the crucial biological meanings that define the waveforms of each new insect species recorded by EPG. By synchronizing AC EPG waveforms with high-magnification video of H. coagulata stylet penetration in artifical diet, we correlated stylet activities with three previously described EPG pathway waveforms, A1, B1 and B2, as well as one ingestion waveform, C. Waveform A1 occured at the beginning of stylet penetration. This waveform was correlated with salivary sheath trunk formation, repetitive stylet movements involving retraction of both maxillary stylets and one mandibular stylet, extension of the stylet fascicle, and the fluttering-like movements of the maxillary stylet tips. Waveform B1 was ubitquious, interspersed throughout the other waveforms. B1 sub-type B1w was correlated with salivation followed by maxillary tip fluttering. This tip fluttering also occurred before and during B1 sub-type B1s, but was not directly correlated with either the occurrence or frequency of this waveform. Waveform B2 was correlated with sawing-like maxillary stylet movements, which usually occurred during salivary sheath branching. Waveform C was correlated with ingestion. Fluid outflow was also observed as a mechanism to clear the maxillary tips from debris during waveform C. This detailed understanding of stylet penetration behaviors of H. coagulata is an important step toward identifying the instant of bacterial inoculation which, in turn, will be applied to studies of disease epidemiology and development of host plant resistance.