exoskeleton

Reader's Digest 12月号のAnts in My Pantsと題された、蟻に悩まされ、蟻の駆除に四苦八苦する様をユーモラスに書いた記事からです。　Ants in My Pants自体も面白く分かりやすい表現ですが、かなり前に取り上げた難しい単語 "formication" （蟻走感 Ref. http://blog.alc.co.jp/blog/3302827/archive/2007/04/15）を思い出させます。今日取り上げる単語 "exoskelton" が出てくる個所を上記の記事から引用します。
I lifted the pot for a peek. There were squillions of them forming a writhing mass of legs, eggs, wings and queens. It was a hedonistic display of ant supremacy in which they openly flaunted their abundance and exoskeleton physique.
"exoskeleton" は骨の一種の様だが蟻に骨はあったかしら？ 辞書で正確な意味を調べます。
・American Heritage Dictionary: A hard outer structure, such as the shell of an insect or crustacean, that provides protection or support for an organism.
どの辞書も上記と同様の説明しかありませんが、Webの百科事典、Wikipediaには詳しい説明があります。その一部を引用します。
An exoskeleton is an external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Some example of exoskeleton animals include insects such as grasshoppers and cockroaches, and crustaceans such as crabs and lobsters. The shells of the various groups of shelled mollusks, including those of snails, clams, tusk shells, chitons and nautilus are also exoskeletons.