The Insect Nervous System. The basic insect nervous system bauplan consists of a series of body segments, each equipped with a pair of connected ganglia, with a paired nerve cord connecting adjacent ganglia in each segment. Before starting an insect collection, one should know how to properly capture, kill, mount, and label the insect. Not only does it give the collector much enjoyment. The phenomenon of monarch migration in North America is well known, and quite extraordinary in the insect world. There are no other insects in the world. An insect mechanosensitive trichoid sensillum - in other words a senor for mechanical movement, in this case touch. When the hair (seta) is deflected, the stimulus is. The ganglia are bulbous structures consisting of neuron cell- bodies and supporting or glial cells and acts as a local processor or computer. This plan is variously modified in the various types, but in all cases the ganglia of the head segment form a fused mass, situated above the oesophagus (esophagus) of the gut, and called the supraoesophageal ganglion. This is connected by a pair of nerve trunks (connectives or commissures) that course around the oesophagus on either side and join to the suboesophageal ganglion (SOG or SEG) situated beneath the oesophagus. Many consider only the supraoesophageal ganglion to constitute the insect brain, others (including myself) consider the SOG as part of the brain. The relative size of the brain species.
Section 5 - Introduction to general taxonomy and biology/ ecology of stored products insect pests. Contents - Previous - Next. The classification of storase insects. One of the most familiar insects in the world is the Honeybee. This member of the insect order Hymenoptera plays a key role in the human and natural world. The online version of Advances in Insect Physiology at ScienceDirect.com, the world's leading platform for high quality peer-reviewed full-text journals. Fly-in-the-batter cookies: Make chocolate chip or oatmeal cookies, adding raisins (flies) or chocolate sprinkles (gnats). Fly-in-the-batter pudding: Vanilla. That of the diving beetle Dytiscus is about 1/4. Formica) is about 1/2. The brain is generally larger in those insects that have more complex social lives. Although much smaller than a human brain, containing only one thousandth as many cells, it is still immensely complex. There is also less replication of function - fewer neurons perform each function. The supraoesophageal ganglion consists of several fused ganglia or lobes. The paired ganglia of the first (frontmost) head segment form the protocerebrum, concerned with vision, time- keeping, higher functions, memory and combining information from different sensory modalities. Those of the segment segment form the deutocerebrum, which is concerned with processing sensory inputs from the antennae, and also the labial palps and parts of the tegument (body wall). The optic lobe connects directly to the sensory cells (retinula cells) in the retina of the compound eye. It contains three distinct regions (neuropils): the lamina, medulla and lobula, where processing of visual signals begins. The protocerebrum also receives inputs via the ocelli, when present, via the ocellar nerves. The mushroom bodies (MB, corpora pedunculata, 'stalked bodies') are best developed in social insects, making up 2. Formica). These are thought to function as higher centres responsible for the most sophisticated computations occurring in the insect brain. Each consists of a topmost cap and a stalk or peduncle (which branches into at least two lobes). The cap consists of a pair of cup- like structures, the medial calyx and the lateral calyx (plural of calyx is calyces). The mushroom bodies receive sensory inputs from the lobula of the optic lobe and from the antennal lobes of the deutocerebrum. Most sensory inputs enter the MB through the calyx. There are about 1. Kenyon cells, in each mushroom body. These neurons have tree- like branching dendrites which receive inputs in the calyces of the MB, a single axon which extends down the stalk of the MB and then gives of branches to two lobes of the MB. Dragonfly mushroom bodies have no calyces and no Kenyon cells. The mushroom bodies are also involved in learning, and in the honeybee have been shown to process memories, transferring data from short- term memory (STM) into long- term memory (LTM). The central body receives inputs from the mushroom bodies and integrates sensory inputs from different sensory modalities (such as small and vision) - so- called multimodal sensory perception. It functions as an activating centre, switching on appropriate locomotor activity patterns which are central programslocated in the thoracic ganglia. That is it instructs the thoracic ganglia which programs to run - programs that control the legs and wings. These hard- wired programs are sometimes called central pattern generators and require no sensory input for their execution, though sensory inputs may start and stop these programs or modify them slightly. The pars intercerebralis is a mass of cell bodies, including neurosecretory cells which send their axons to the pair of corpora cardiaca (see the neuroendocrine system in insect development). The corpora cardiac are sometimes fused into a single medial ganglion. They send out nerves to innervate the dorsal blood vessel, forming a cardio- aortic system, which controls the rate of heart beat, as well as having a secretory hormona lfunction. Did you know? The insect brain contains about 1. Biological Clocks. Another function associated with the protocerebrum is time- keeping. Insect activity is timed with the daily light/dark cycle - the circadian cycle ('ciracdian' means 'about a day', the exact time being set each day according to environmental cues such as the length of daylight). This timing is due to internal clocks within the insect, which update themselves according to external cues from the environment (zeitgeibers or time- givers) such as the number of hours of light and dark. Many body parts and organs have their own circadian clocks, indeed each cell appears capable of keeping time, but these appear to be set and synchronised by a central master clock, which resides in the protocerebrum and is both neural and hormonal. In some insects, a master clock is found in each optic lobe, which makes sense as these process light signals. There is also a daily movement of screening pigments in the ommatidia of the compound eye, as the insect adjusts to night- time darkness by increasing the sensitivity of its retina (it will continue to do this at the correct time for days when kept in constant light or dark for several days, so the response is coordinated, in part, by a central clock). Severing of the optic lobes prevents these clocks from synchronising bodily activities. In other species, however, the clock is only abolished if the brain is cut in two, which suggests that it may reside in the central body. Deutocerebrum. This consists of two nerve centres - the main antennal lobe (AL) and the smaller antennal mechanosensory and motor centre (AMMC) or dorsal lobe. The AL receives inputs from the third (terminal) antennal segment (the flagellum, which is made- up of sub- segments called flagellomeres) via the antennal nerves. It contains from less than 1. Inputs to the AL appear to be mainly or exclusively from chemoreceptors (i. Each antenna sends signals to the AL on the same side of the head (ipsilateral pathways) although some may also send signals to the AL on the opposite side (contralateral pathways). Each glomerulus is a region of neuropil (nerve cell processes and synapses) where computations occur. It is thought that each glomerulus may, in some species at least, receive inputs from a specific class of receptor (sensor) on the antenna. For example, in the males of some species there is a specially large glomerulus, called the macroglomerular complex (MGC)which receives inputs from pheromone olfactory sensors on the antenna. The AL does not receive one input line from each chemoreceptor, as sensors of the same type converge - their axons fuse into a smaller number of axons in the antennal nerve (typically inputs from 1. These sensory input axons, and also input axons from the CB of the protocerebrum, synapse with local interneurones within the AL (amacrine cells). Outputs from the AL are carried along the axons of output neurons to the MB of the protocerebrum. The AMMC receives mechanosensory inputs from mechanosensors (mechanoreceptors)on the first two antennal segments (scape and pedicel) via the antennal nerves. It also sends motor outputs to the muscles of the scape. It also receives inputs from mechanosensors on the labial palps, some tegument (body wall) mechanosensors, and some inputs from the flagellum (possibly from the mechanosensors found on the flagellum). The antennal nerve is therefore a mixed nerve - containing both sensory and motor axons. Some of the antennal mechanoreceptors also send outputs to the SOG, the protocerebrum and the thoracic ganglia. Tritocerebrum and Stomatogastric System. The frontal ganglion (FG) is an additional free and single (unpaired) median (median = in the midline) ganglion that is connected by a pair of bilateral connectives to the tritocerebrum. In the locust, the HG sends out one pair of outer oesophageal nerves (and one pair of inner oesophageal nerves (ventricular nerves). Each of the latter terminates in a ventricular ganglion (ingluvial ganglion) on the crop of the foregut (see insect nutrition). These then control crop movements. In Dytiscus, it has been shown that the FG also controls swallowing. Thus, the tritocerebrum and frontal ganglion control the foregut, forming the stomatogastric system. The tritocerebrum also innervates the labrum. Suboesophageal Ganglion. The suboesophageal ganglion (SOG) and the segmental ganglia of the double ventral nerve- cord each send out pairs of nerves, one of which innervates the pair of spiracles on that segment and so help regulate breathing. The SOG is a composite ganglion, formed by fusion of the ganglia from the mandibular, maxillary and labial segments of the head and the SOG also sends out nerves to the mouthparts (mandibles, palps, etc.) and so controls feeding behaviours. The Ventral Nerve Cord. From the suboesophageal ganglion two connectives or nerve cords run back along the ventral side (underside) of the insect. These connect to the thoracic ganglion of the first thoracic segment, T1, which is actually a pair of ganglia, more- or- less fused into a single structure. T1 then gives off two connectives to the second thoracic ganglion, T2 and the sequence continues with a chain of connected ganglia running throughout the length of the insect, in the basic plan. Thus, we say that insects have a double ganglionated ventral nerve cord (VNC). Each ganglion functions as a local processor, regulating the functions of its body segment. The thoracic ganglia are especially well- developed as they have to carry out complex computations to generate patterns of movement in the legs and wings.
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