Editing Diapause (section)

==Regulation==
Diapause in insects is regulated at several levels. Environmental stimuli interact with genetic pre-programming to affect [[neuron]]al signalling, [[endocrine]] pathways, and, eventually, metabolic and enzymatic changes.

===Environmental===
Environmental regulators of diapause generally display a characteristic [[season|seasonal pattern]]. In [[temperate]] regions, photoperiod is the most reliable cues of seasonal change.<ref name="Huffaker" /> This informs entry into reproductive diapause for many northern insects, including the fruit fly ''[[Drosophila montana]].''<ref>{{Cite journal|last1=Salminen|first1=T. S.|last2=Vesala|first2=L.|last3=Hoikkala|first3=A.|date=2012-12-01|title=Photoperiodic regulation of life-history traits before and after eclosion: Egg-to-adult development time, juvenile body mass and reproductive diapause in ''Drosophila montana''|journal=Journal of Insect Physiology|volume=58|issue=12|pages=1541–1547|doi=10.1016/j.jinsphys.2012.09.007|pmid=23026647|bibcode=2012JInsP..58.1541S |issn=0022-1910}}</ref> Depending on the season in which diapause occurs, either short or long days can act as token stimuli. Insects may also respond to changing day length as well as relative day length. Temperature may also act as a regulating factor, either by inducing diapause or, more commonly, by modifying the response of the insect to photoperiod.<ref name="Huffaker" /> Insects may respond to thermoperiod, the daily fluctuations of warm and cold that correspond with night and day, as well as to absolute or cumulative temperature. This has been observed in many moth species including the [[Indian mealmoth]], where individuals diapause in different developmental stages due to environmental temperature.<ref>{{Cite journal|last=Tzanakakis|first=M. E.|date=1959-11-01|title=An ecological study of the Indian-meal mothPlodia interpunctella(Hübner) with emphasis on diapause|journal=Hilgardia|language=en|volume=29|issue=5|pages=205–246|doi=10.3733/hilg.v29n05p205|issn=0073-2230|doi-access=free}}</ref> Food availability and quality may also help regulate diapause. In the [[desert locust]], ''Schistocerca gregaria'', a plant [[hormone]] called [[gibberellin]] stimulates [[reproduction|reproductive]] development.<ref>{{cite journal |last1= Ellis |first1= P.E. |last2= Carlisle |first2= D.B. |last3= Osborne |first3= D.J. |year= 1965 |title= Desert locusts: sexual maturation delayed by feeding on senescent vegetation |journal= Science |volume= 149 |issue= 3683 |pages= 546–547 |doi=10.1126/science.149.3683.546 |pmid=17843190|bibcode= 1965Sci...149..546E |s2cid= 34321076 }}</ref> During the dry season, when their food plants are in [[senescence]] and lacking gibberellin, the locusts remain immature and their reproductive tracts do not develop.

===Neuroendocrine===
The [[neuroendocrinology|neuroendocrine]] system of insects consists primarily of neurosecretory cells in the [[brain]], the corpora cardiaca, corpora allata and the prothoracic glands.<ref name="Tauber" /> There are several key [[hormone]]s involved in the regulation of diapause: [[juvenile hormone]] (JH), diapause hormone (DH), and [[prothoracicotropic hormone|prothoracicotropic hormone (PTTH)]].<ref name="Denlinger">{{cite journal |last1= Denlinger |first1= D.L. |year= 2002 |title= Regulation of diapause |journal= Annual Review of Entomology |volume= 47 |pages= 93–122 |doi= 10.1146/annurev.ento.47.091201.145137|pmid= 11729070 }}</ref>

Prothoracicotropic hormone stimulates the prothoracic glands to produce [[ecdysteroids]] that are required to promote development.<ref name="Denlinger" /> Larval and pupal diapauses are often regulated by an interruption of this connection, either by preventing release of prothoracicotropic hormone from the brain or by failure of the prothoracic glands to respond to prothoracicotropic hormone.

The corpora allata is responsible for the production of [[juvenile hormone]] (JH). In the bean bug, ''Riptortus pedestris'', clusters of [[neurons]] on the [[protocerebrum]] called the [[pars lateralis]] maintain reproductive diapause by inhibiting JH production by the [[corpora allata]].<ref>{{cite journal |last1= Shimokawa |first1= K. |last2= Numata |first2= H. |last3= Shiga |first3= S. |year= 2008 |title= Neurons important for the photoperiodic control of diapause in the bean bug, ''Riptortus pedestris'' |journal= Journal of Comparative Physiology |volume= 194 |issue= 8|pages= 751–762 |doi=10.1007/s00359-008-0346-y|pmid= 18546002 |s2cid= 28631269 }}</ref> Adult diapause is often associated with the absence of JH, while larval diapause is often associated with its presence.

In adults, absence of JH causes degeneration of flight [[muscles]] and [[atrophy]] or cessation of development of reproductive tissues, and halts mating behaviour. The presence of JH in larvae may prevent moulting to the next larval [[instar]], though successive stationary moults may still occur.<ref>{{cite journal |last1= Yin |first1= C.M. |last2= Chippendale |first2= G.M. |year= 1979 |title= Diapause of the Southwestern Corn Borer, ''Diatraea grandiosella'': further evidence showing juvenile hormone to be the regulator |journal= Journal of Insect Physiology |volume= 25 |issue= 6|pages= 513–523 |doi=10.1016/s0022-1910(79)80010-4|bibcode= 1979JInsP..25..513Y }}</ref> In the corn borer, ''Diatraea gradiosella'', JH is required for the accumulation by the fat body of a storage [[protein]] that is associated with diapause.<ref>{{cite journal |last1= Brown |first1= J.J. |last2= Chippendale |first2= G.M. |year= 1978 |title= Juvenile hormone and a protein associated with the larval diapause of the Southwestern Corn Borer, ''Diatraea grandiosella'' |journal= Insect Biochemistry |volume= 8 |issue= 5|pages= 359–397 |doi=10.1016/0020-1790(78)90022-7}}</ref>

Diapause hormone regulates [[embryo]]nic diapause in the eggs of the [[silkworm]] moth, ''Bombyx mori''.<ref>{{cite journal |last1= Horie |first1= Y. |last2= Kanda |first2= T. |last3= Mochida |first3= Y. |year= 2000 |title= Sorbitol as an arrester of embryonic development in diapausing eggs of the silkworm, ''Bombyx mori'' |journal= Journal of Insect Physiology |volume= 46 |issue= 6|pages= 1009–1016 |doi=10.1016/s0022-1910(99)00212-7|pmid= 10802114 |bibcode= 2000JInsP..46.1009H }}</ref> DH is released from the [[subesophageal ganglion]] of the mother and triggers [[trehalase]] production by the [[ovaries]]. This generates high levels of [[glycogen]] in the [[egg (biology)|eggs]], which is converted into the polyhydric alcohols [[glycerol]] and sorbitol. [[Sorbitol]] directly inhibits the development of the embryos. [[Glycerol]] and [[sorbitol]] are reconverted into [[glycogen]] at the termination of diapause.