Neosomy

Neosomy is the formation of new external structure in an active stage of an invertebrate, in a taxon that normally only changes during moulting.

For example, an adult female Tunga monositus starts out at 1 mm long and, after feeding and growing, increases in volume by 1000 times, becomes circular in shape and forms anterior lobes that the head is retracted between (for protection).

[5] Similar to the aforementioned fleas, bat flies of genus Ascodipteron have females which attach to a host, then lose their limbs and transform into neosomes, with the head and thorax withdrawn into a swollen abdomen.

Queen termites include the largest neosomes among terrestrial arthropods, with some exceeding 12.5 cm in length.

In Termitomimus and Nasutimimus rove beetles, the abdomen is similar in shape to a termite nymph and may be used in tactile mimicry.