Editing Beetle (section)

==Anatomy and physiology==<!--or, Body systems-->
[[File:Internal morphology of Coleoptera.svg|upright=1.7<!--diagram with small captions-->|thumb|A beetle's body systems]]

===Digestive system===
The [[Digestion|digestive system]] of beetles is primarily adapted for a herbivorous diet. Digestion takes place mostly in the anterior [[midgut]], although in predatory groups like the [[Carabidae]], most digestion occurs in the crop by means of midgut enzymes. In the [[Elateridae]], the larvae are liquid feeders that extraorally digest their food by secreting enzymes.<ref name=insenc/> The alimentary canal basically consists of a short, narrow [[pharynx]], a widened expansion, the crop, and a poorly developed [[gizzard]]. This is followed by the midgut, that varies in dimensions between species, with a large amount of [[cecum]], and the hindgut, with varying lengths. There are typically four to six [[Malpighian tubule]]s.<ref name="Gilliott"/>

===Nervous system===
The [[nervous system]] in beetles contains all the types found in insects, varying between different species, from three thoracic and seven or eight abdominal ganglia which can be distinguished to that in which all the thoracic and abdominal ganglia are fused to form a composite structure.<ref name=insenc/>

===Respiratory system===
[[File:DytiscusSpiracles.png|thumb|''[[Dytiscus]]'' [[Spiracle (arthropods)|spiracle]]s (right) on upper side of abdomen, normally covered by the elytra, are in contact with an air bubble when the beetle dives.|left|175x175px]]

Like most insects, beetles inhale air, for the [[oxygen]] it contains, and exhale [[carbon dioxide]], via a [[invertebrate trachea|tracheal system]]. Air enters the body through [[Spiracle (arthropods)|spiracle]]s, and circulates within the haemocoel in a system of [[Invertebrate trachea|tracheae]] and tracheoles, through whose walls the gases can diffuse.<ref name=insenc/>

Diving beetles, such as the [[Dytiscidae]], carry a bubble of air with them when they dive. Such a bubble may be contained under the elytra or against the body by specialized [[hydrophobic]] hairs. The bubble covers at least some of the spiracles, permitting air to enter the tracheae.<ref name=insenc/> The function of the bubble is not only to contain a store of air but to act as a [[Gill#Plastron|physical gill]]. The air that it traps is in contact with oxygenated water, so as the animal's consumption depletes the oxygen in the bubble, more oxygen can diffuse in to replenish it.<ref>{{cite journal|doi=10.1242/jeb.070276 |pmid=23255190 |title=Physical gills in diving insects and spiders: Theory and experiment |journal=The Journal of Experimental Biology |volume=216 |issue=2 |pages=164–70 |year=2012 |last1=Seymour |first1=Roger S. |last2=Matthews |first2=Philip G. D. |doi-access=free }}</ref> Carbon dioxide is more soluble in water than either oxygen or nitrogen, so it readily diffuses out faster than in. Nitrogen is the most plentiful gas in the bubble, and the least soluble, so it constitutes a relatively static component of the bubble and acts as a stable medium for respiratory gases to accumulate in and pass through. Occasional visits to the surface are sufficient for the beetle to re-establish the constitution of the bubble.<ref>{{cite book |last=Schmidt-Nielsen |first=Knut |title=Animal Physiology: Adaptation and Environment |chapter-url=https://books.google.com/books?id=Af7IwQWJoCMC&pg=PA55|edition=5th |date=January 15, 1997|publisher=[[Cambridge University Press]] |isbn=978-0-521-57098-5 |page=55 |chapter=Insect Respiration}}</ref>

===Circulatory system===
Like other insects, beetles have [[open circulatory system]]s, based on [[hemolymph]] rather than blood. As in other insects, a segmented tube-like heart is attached to the dorsal wall of the [[circulatory system#Nonhuman|hemocoel]]. It has paired inlets or ''ostia'' at intervals down its length, and circulates the hemolymph from the main cavity of the haemocoel and out through the anterior cavity in the head.<ref>{{cite book |last=Miller |first=T. A. |editor1=Kerkut, G. A. |editor2=Gilbert, L. I. |title=Comprehensive Insect Physiology, Biochemistry and Pharmacology. Volume 3: Integument, Respiration and Circulation |publisher=Pergamom Press |date=1985 |pages=289–355 |chapter=Chapter 8: Structure and Physiology of the Circulatory System |isbn=978-0-08-030804-3}}</ref>

===Specialized organs===
Different glands are specialized for different pheromones to attract mates. Pheromones from species of [[Rutelinae]] are produced from [[epithelial cell]]s lining the inner surface of the apical abdominal segments; amino acid-based pheromones of [[Melolonthinae]] are produced from eversible glands on the abdominal apex. Other species produce different types of pheromones. [[Dermestid]]s produce [[ester]]s, and species of [[Elateridae]] produce [[aldehyde|fatty acid-derived aldehyde]]s and [[acetate]]s.<ref name=insenc/> To attract a mate, fireflies ([[Lampyridae]]) use modified fat body cells with transparent surfaces backed with reflective uric acid crystals to produce light by [[bioluminescence]]. Light production is highly efficient, by oxidation of [[Firefly luciferin|luciferin]] catalyzed by enzymes ([[luciferase]]s) in the presence of [[adenosine triphosphate]] (ATP) and oxygen, producing [[oxyluciferin]], carbon dioxide, and light.<ref name=insenc/>

[[Tympanal organ]]s or hearing organs consist of a membrane (tympanum) stretched across a frame backed by an air sac and associated sensory neurons, are found in two families.<ref name="Scoble">{{cite book |author=Scoble, M. J. |title=The Lepidoptera: Form, function, and diversity |url=https://archive.org/details/lepidopteraformf0000scob |url-access=registration |year=1992 |publisher=Oxford University Press |isbn=978-1-4020-6242-1}}</ref> Several species of the genus ''[[Cicindela]]'' (Carabidae) have hearing organs on the dorsal surfaces of their first abdominal segments beneath the wings; two tribes in the [[Dynastinae]] (within the [[Scarabaeidae]]) have hearing organs just beneath their pronotal shields or neck membranes. Both families are sensitive to ultrasonic frequencies, with strong evidence indicating they function to detect the presence of bats by their ultrasonic echolocation.<ref name=insenc/>