Maxilla

\ postmentum J

prementum maxillary palp

paraglossa hypopharynx each consisting of a basal part composed of the proximal cardo and the more distal stipes and, attached to the stipes, two lobes - the mesal lacinia and the lateral galea - and a lateral, segmented maxillary palp, or palpus (plural: palps or palpi). Functionally, the maxillae assist the mandibles in processing food; the pointed and sclerotized lacinae hold and macerate the food, whereas the galeae and palps bear sensory setae (mechanoreceptors) and chemoreceptors which sample items before ingestion. The appendages of the sixth segment of the head are fused with the sternum to form the labium, which is believed to be homologous to the second maxillae of Crustacea. In prognathous insects, such as the earwig, the labium attaches to the ventral surface of the head via a ventromedial sclero-tized plate called the gula (Fig. 2.10). There are two main parts to the labium: the proximal postmentum, closely connected to the posteroventral surface of the head and sometimes subdivided into a submentum and mentum; and the free distal prementum, typically bearing a pair of labial palps lateral to two pairs of lobes, the mesal glossae (singular: glossa) and the more lateral paraglossae (singular: paraglossa). The glossae and paraglossae, including sometimes the distal part of the prementum to which they attach, are known collectively as the ligula; the lobes may be variously fused or reduced as in Forficula (Fig. 2.10), in which the glossae are absent. The prementum with its lobes forms the floor of the preoral cavity (functionally a "lower lip"), whereas the labial palps have a sensory function, similar to that of the maxillary palps.

During insect evolution, an array of different mouth-part types have been derived from the basic design described above. Often feeding structures are characteristic of all members of a genus, family, or order of insects, so that knowledge of mouthparts is useful for both taxonomic classification and identification, and for ecological generalization (see section 10.6). Mouthpart structure is categorized generally according to feeding method, but mandibles and other components may function in defensive combat or even male-male sexual contests, as in the enlarged mandibles on certain male beetles (Lucanidae). Insect mouthparts

Fig. 2.10 (opposite) Frontal view of the head and dissected mouthparts of an adult of the European earwig, Forficula auricularia (Dermaptera: Forficulidae). Note that the head is prognathous and thus a gular plate, or gula, occurs in the ventral neck region.

Bee Head Frontal Glossa

Fig. 2.11 Frontal view of the head of a worker honey bee, Apis mellifera (Hymenoptera: Apidae), with transverse section of proboscis showing how the "tongue" (fused labial glossae) is enclosed within the sucking tube formed from the maxillary galae and labial palps. (Inset after Wigglesworth 1964.)

Fig. 2.11 Frontal view of the head of a worker honey bee, Apis mellifera (Hymenoptera: Apidae), with transverse section of proboscis showing how the "tongue" (fused labial glossae) is enclosed within the sucking tube formed from the maxillary galae and labial palps. (Inset after Wigglesworth 1964.)

have diversified in different orders, with feeding methods that include lapping, suctorial feeding, biting, or piercing combined with sucking, and filter feeding, in addition to the basic chewing mode.

The mouthparts of bees are of a chewing and lapping-sucking type. Lapping is a mode of feeding in which liquid or semi-liquid food adhering to a protrusible organ, or "tongue", is transferred from substrate to mouth. In the honey bee, Apis mellifera (Hymenoptera: Apidae), the elongate and fused labial glossae form a hairy tongue, which is surrounded by the maxillary galeae and the labial palps to form a tubular proboscis containing a food canal (Fig. 2.11). In feeding, the tongue is dipped into the nectar or honey, which adheres to the hairs, and then is retracted so that adhering liquid is carried into the space between the galeae and labial palps. This back-and-forth glossal movement occurs repeatedly. Movement of liquid to the mouth apparently results from the action of the cibarial pump, facilitated by each retraction of the tongue pushing liquid up the food canal. The maxillary laciniae and palps are rudimentary and the paraglossae embrace the base of the tongue, directing saliva from the dorsal salivary orifice around into a ventral channel from whence it is transported to the flabellum, a small lobe at the glossal tip; saliva may dissolve solid or semi-solid sugar. The sclerotized, spoon-shaped mandibles lie at the base of the proboscis and have a variety of functions, including the manipulation of wax and plant resins for nest construction, the feeding of larvae and the queen, grooming, fighting, and the removal of nest debris including dead bees.

Most adult Lepidoptera and some adult flies obtain their food solely by sucking up liquids using suctorial (haustellate) mouthparts that form a proboscis or rostrum (Figs. 2.12-2.14). Pumping of the liquid food is achieved by muscles of the cibarium and/or pharynx. The proboscis of moths and butterflies, formed from the greatly elongated maxillary galeae, is extended (Fig. 2.12 a) by increases in hemolymph ("blood") pressure. It is loosely coiled by the inherent elasticity of the cuticle, but tight coiling requires contraction of intrinsic muscles (Fig. 2.12b). A cross-section of the proboscis (Fig. 2.12c) shows how the food canal, which opens basally into the cibarial pump, is formed by apposition and interlocking of the two galeae. The proboscis of some male hawkmoths (Sphingidae), such as that of Xanthopan morgani, can attain great length (Fig. 11.8).

A few moths and many flies combine sucking with piercing or biting. For example, moths that pierce fruit and exceptionally suck blood (species of Noctuidae) have spines and hooks at the tip of their proboscis which are rasped against the skins of either ungulate mammals or fruit. For at least some moths, penetration is effected by the alternate protraction and retraction of the two galeae that slide along each other. All dipterans typically have a tubular sucking organ, the proboscis, comprising elongate mouthparts (usually including the labrum) (Fig. 2.13a). A biting-and-sucking type of proboscis appears to be a primitive dipteran feature. Although biting functions have been lost and regained with modifications more than once, blood feeding is frequent, and leads to the importance of the Diptera as vectors of disease. Blood-feeding flies have a variety of skin-penetration and feeding mechanisms. In the

Fig. 2.12 Mouthparts of a white butterfly, Pierissp. (Lepidoptera: Pieridae). (a) Positions of the proboscis showing, from left to right, at rest, with proximal region uncoiling, with distal region uncoiling, and fully extended with tip in two of many possible different positions due to flexing at "knee bend". (b) Lateral view of proboscis musculature. (c) Transverse section of the proboscis in the proximal region. (After Eastham & Eassa 1955.)

Fig. 2.12 Mouthparts of a white butterfly, Pierissp. (Lepidoptera: Pieridae). (a) Positions of the proboscis showing, from left to right, at rest, with proximal region uncoiling, with distal region uncoiling, and fully extended with tip in two of many possible different positions due to flexing at "knee bend". (b) Lateral view of proboscis musculature. (c) Transverse section of the proboscis in the proximal region. (After Eastham & Eassa 1955.)

Mouthpart Thrips

Fig. 2.13 Female mosquito mouthparts in (a) frontal view; (b) transverse section. ((a) After Freeman & Bracegirdle 1971; (b) after Jobling 1976.)

Fig. 2.14 Mouthparts of adult Diptera. (a) House fly, Musca (Muscidae). (b) Stable fly, Stomoxys (Muscidae). (After Wigglesworth 1964.)

Fig. 2.13 Female mosquito mouthparts in (a) frontal view; (b) transverse section. ((a) After Freeman & Bracegirdle 1971; (b) after Jobling 1976.)

Fig. 2.14 Mouthparts of adult Diptera. (a) House fly, Musca (Muscidae). (b) Stable fly, Stomoxys (Muscidae). (After Wigglesworth 1964.)

"lower" flies such as mosquitoes and black flies, and the Tabanidae (horse flies, Brachycera), the labium of the adult fly forms a non-piercing sheath for the other mouthparts, which together contribute to the piercing structure. In contrast, the biting calyptrate dipterans (Brachycera: Calyptratae, e.g. stable flies and tsetse flies) lack mandibles and maxillae and the principal piercing organ is the highly modified labium.

The blood-feeding female nematocerans - Culicidae (mosquitoes); Ceratopogonidae (biting midges); Psy-chodidae: Phlebotominae (sand flies); and Simuliidae (black flies) - have generally similar mouthparts, but differ in proboscis length, allowing penetration of the host to different depths. Mosquitoes can probe deep in search of capillaries, but other blood-feeding nematocerans operate more superficially where a pool of blood is induced in the wound. The labium ends in two sensory labella (singular: labellum), and forms a protective sheath for the functional mouthparts (Fig. 2.13a). Enclosed are serrate-edged, cutting mandibles and maxillary lacinia, the curled labrum-epipharynx, and the hypopharynx, all of which are often termed stylets (Fig. 2.13b). When feeding, the labrum, mandibles, and laciniae act as a single unit driven through the skin of the host. The flexible labium remains bowed outside the wound. Saliva, which may contain anticoagulant, is injected through a salivary duct that runs the length of the sharply pointed and often toothed hypopharynx. Blood is transported up a food canal formed from the curled labrum sealed by either the paired mandibles or the hypopharynx. Capillary blood can flow unaided, but blood must be sucked or pumped from a pool with pumping action from two muscular pumps: the cibarial located at the base of the food canal, and the pharyngeal in the pharynx between the cibarium and midgut.

Many mouthparts are lost in the "higher" flies, and the remaining mouthparts are modified for lapping food using pseudotracheae of the labella as "sponges", as in a house fly (Muscidae: Musca) (Fig. 2.14a). With neither mandibles nor maxillary lacinia to make a wound, blood-feeding cyclorrhaphans often use modified labella, in which the inner surfaces are adorned with sharp teeth, as in stable flies (Muscidae: Stomoxys) (Fig. 2.14b). Through muscular contraction and relaxation, the labellar lobes dilate and contract repeatedly, creating an often painful rasping of the labellar teeth to give a pool of blood. The hypopharynx applies saliva, which is dissipated via the labellar pseudotracheae. Uptake of blood is via capillary action through "food furrows" lying dorsal to the pseudotracheae, with the aid of three pumps operating synchronously to produce continuous suction from labella to pharynx. A prelabral pump produces the contractions in the labella, with a more proximal labral pump linked via a feeding tube to the cibarial pump.

The mouthparts of adult flies and their use in feeding have implications for disease transmission. Shallow-feeding species such as black flies are more involved in transmission of microfilariae, such as those of Onchocerca, which aggregate just beneath the skin, whereas deeper feeders such as mosquitoes transmit pathogens that circulate in the blood. The transmission from fly to host is aided by the introduction of saliva into the wound, and many parasites aggregate in the salivary glands or ducts. Filariae, in contrast, are too large to enter the wound through this route, and leave the insect host by rupturing the labium or labella during feeding.

Other mouthpart modifications for piercing and sucking are seen in the true bugs (Hemiptera), thrips (Thysanoptera), fleas (Siphonaptera), and sucking lice (Psocodea: Anoplura). In each order different mouthpart components form needle-like stylets capable of piercing the plant or animal tissues upon which the insect feeds. Bugs have extremely long, thin, paired mandibular and maxillary stylets, which fit together to form a flexible stylet-bundle containing a food canal and a salivary canal (Taxobox 20). Thrips have three stylets - paired maxillary stylets (laciniae) plus the left mandibular one (Fig. 2.15). Sucking lice have three

Mouthpart Thrips
Fig. 2.15 Head and mouthparts of a thrips, Thripsaustralis (Thysanoptera: Thripidae). (a) Dorsal view of head showing mouthparts through prothorax. (b) Transverse section through proboscis. The plane of the transverse section is indicated by the dashed line in (a). (After Matsuda 1965; CSIRO 1970.)

Fig. 2.16 Head and mouthparts of a sucking louse, Pediculus (Psocodea: Anoplura: Pediculidae). (a) Longitudinal section of head (nervous system omitted). (b) Transverse section through eversible proboscis. The plane of the transverse section is indicated by the dashed line in (a). (After Snodgrass 1935.)

Fig. 2.16 Head and mouthparts of a sucking louse, Pediculus (Psocodea: Anoplura: Pediculidae). (a) Longitudinal section of head (nervous system omitted). (b) Transverse section through eversible proboscis. The plane of the transverse section is indicated by the dashed line in (a). (After Snodgrass 1935.)

stylets - the hypopharyngeal (dorsal), the salivary (median), and the labial (ventral) - lying in a ventral sac of the head and opening at a small eversible proboscis armed with internal teeth that grip the host during blood-feeding (Fig. 2.16). Fleas possess a single stylet derived from the epipharynx, and the laciniae of the maxillae form two long cutting blades that are ensheathed by the labial palps (Fig. 2.17). The Hemiptera and the Thysanoptera are sister groups and belong to the same assemblage as the Psocodea (Fig. 7.5), with the lice originating from a psocid-like ancestor with mouthparts of a more generalized, man-dibulate type. The Siphonaptera are distant relatives of the other three taxa; thus similarities in mouth-part structure among these orders result largely from parallel or, in the case of fleas, convergent evolution.

Odonata Labium
Fig. 2.17 Head and mouthparts of a human flea, Pulex irritans (Siphonaptera: Pulicidae): (a) lateral view of head; (b) transverse section through mouthparts. The plane of the transverse section is indicated by the dashed line in (a). (After Snodgrass 1946; Herms & James 1961.)

Slightly different piercing mouthparts are found in antlions and the predatory larvae of other lacewings (Neuroptera). The stylet-like mandible and maxilla on each side of the head fit together to form a sucking tube (Fig. 13.2c), and in some families (Chrysopidae, Myrmeleontidae, and Osmylidae) there is also a narrow poison channel. Generally, labial palps are present, maxillary palps are absent, and the labrum is reduced. Prey is seized by the pointed mandibles and maxillae, which are inserted into the victim; its body contents are digested extra-orally and sucked up by pumping of the cibarium.

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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