Michael Hutchinson / Close-up of a pair of Marsh fritillary butterflies (Euphydryas aurinia) mating, showing tips of abdomens, Devon, England, UK, June.

Alex Hyde / Green Dock Beetle (Gastrophysa viridula) female with huge abdomen swollen with eggs. Peak District National Park, Derbyshire, UK. May.

Konrad Wothe / Red Wood Ant (Formica rufa) colony reacting in defensive behavior by spraying formic acid from a gland in rear of their abdomens, Sweden

Michael Hutchinson / Close-up of a pair of Marsh fritillary butterflies (Euphydryas aurinia) mating, showing tips of abdomens, Devon, England, UK, June.

Nick Upton / Mosquito larvae (Culicidae), filter feeding in a garden pond with the breathing tubes at the ends of their abdomens reaching the surface, Wiltshire, UK, June.

Stephen Dalton / Silver washed fritillary (Argynnis paphia) in flight, Sussex, England, UK, July.

Stephen Dalton / Close up of Orb Weaver Spider (Tetragnathidae) abdomen showing spinnerets and thread being controlled by legs. UK.

Nick Upton / Worker Honey ants with abdomens swollen with honey {Myrmecocystus mimicus} USA

Nick Upton / Worker Honey ants with abdomens swollen with honey {Myrmecocystus mimicus} USA

Mark Moffett / Tarantula (Pseudotheraphosa sp) surrounded by a cloud of barbed toxic hairs which it breaks off by brushing their abdomens with hind legs as a defensive move, Venezuela

Joel Sartore / Photo Ark / Ornate spiny-tailed agama (Uromastyx ornata) portrait, abdomen showing skin markings, Arabia's Wildlife Centre, Sharjah, UAE. Captive.

Will Watson / Short-fringed mining bee (Andrena dorsata) resting on Dandelion (Taraxacum officinale) flower, Herefordshire, England, UK, April.