Editing Dragonfly (section)

===Ecology===

Dragonflies and damselflies are predatory both in the aquatic nymphal and adult stages. Nymphs feed on a range of freshwater invertebrates and larger ones can prey on [[tadpole]]s and small [[fish]].{{sfn|Dijkstra|2006|pages=8–9}} Naiads of one species, ''[[Phanogomphus militaris]]'', may even act as parasites, feeding on the gills of gravid freshwater mussels.<ref>{{cite journal |last1=Levine |first1=Todd D. |last2=Lang |first2=Brian K. |last3=Berg |first3=David J. |title=Parasitism of Mussel Gills by Dragonfly Nymphs |journal=The American Midland Naturalist |year=2009 |volume=162 |issue=1 |pages=1–6 |doi=10.1674/0003-0031-162.1.1}}</ref> Adults capture insect prey in the air, making use of their acute vision and highly controlled flight.

[[File:Dragonfly catches flying prey.webm|thumb|center|thumbtime=0|Dragonfly returns to same perch each time it darts out to catch very small flying prey.]]

The mating system of dragonflies is complex, and they are among the few insect groups that have a system of indirect sperm transfer along with sperm storage, delayed fertilisation, and sperm competition.{{sfn|Dijkstra|2006|pages=8–9}}

Adult males vigorously defend territories near water; these areas provide suitable habitat for the nymphs to develop, and for females to lay their eggs. Swarms of feeding adults aggregate to prey on swarming prey such as emerging flying ants or termites.{{sfn|Dijkstra|2006|pages=8–9}}

[[File:Libellula quadrimaculata m1.jpg|thumb|Habitat preference: A four-spotted chaser, ''[[Libellula quadrimaculata]]'' on an [[emergent vegetation|emergent plant]], the water violet ''[[Hottonia palustris]]'', with submerged vegetation in the background]]

Dragonflies as a group occupy a considerable variety of habitats, but many species, and some families, have their own specific environmental requirements.{{sfn|Dijkstra|2006|pages=13–14}} Some species prefer flowing waters, while others prefer standing water. For example, the Gomphidae (clubtails) live in running water, and the Libellulidae (skimmers) live in still water.{{sfn|Dijkstra|2006|pages=13–14}} Some species live in temporary water pools and are capable of tolerating changes in water level, desiccation, and the resulting variations in temperature, but some genera such as ''[[Sympetrum]]'' (darters)  have eggs and nymphs that can resist drought and are stimulated to grow rapidly in warm, shallow pools, also often benefiting from the absence of predators there.{{sfn|Dijkstra|2006|pages=13–14}} Vegetation and its characteristics including submerged, floating, emergent, or waterside are also important. Adults may require emergent or waterside plants to use as perches; others may need specific submerged or floating plants on which to lay eggs. Requirements may be highly specific, as in ''[[Aeshna viridis]]'' (green hawker), which lives in swamps with the water-soldier, ''[[Stratiotes aloides]]''.{{sfn|Dijkstra|2006|pages=13–14}} The chemistry of the water, including its trophic status (degree of enrichment with nutrients) and [[pH]] can also affect its use by dragonflies. Most species need moderate conditions, not too [[eutrophic]], not too acidic;{{sfn|Dijkstra|2006|pages=13–14}} a few species such as ''[[Sympetrum danae]]'' (black darter) and ''[[Libellula quadrimaculata]]'' (four-spotted chaser) prefer acidic waters such as peat bogs,{{sfn|Dijkstra|2006|pages=243, 272}} while others such as ''[[Libellula fulva]]'' (scarce chaser) need slow-moving, eutrophic waters with reeds or similar waterside plants.{{sfn|Dijkstra|2006|page=246}}<ref name="Ratcliffe2012">{{cite book |last=Ratcliffe |first=Derek |title=A Nature Conservation Review: Volume 1: The Selection of Biological Sites of National Importance to Nature Conservation in Britain |url=https://books.google.com/books?id=YPQaFxH-AZYC&pg=PA378 |date=26 January 2012 |publisher=[[Cambridge University Press]] |isbn=978-0-521-20329-6 |pages=378–379}}</ref>