As my job is microscopy (human pathology) I thought it would be interesting to see how the cup moth caterpillars tick. So I brought a caterpillar in & we processed it as we do for normal biopsies.

Here is a link to caterpillar anatomy http://animals.howstuffworks.com/insects/caterpillar1.htm

The color (green , yellow , red. brown , grey) of the animal is fascinating - pigmentation in creatures is often related to melanin - the brown pigment that gives skin its colour - in the sun , more is produced and light skinned people "tan". Here is the pigment just under the "skin" of the caterpillar - note the brown granules.


Next comes the question of what makes the spines "toxic"?.























The spines branch off a larger support , like branches of a tree. There is some muscle present which causes the spines to stick up.

The spines are hollow and seem to contain red granules (left). Clearly the spines break off into the victim. Now this will cause a "foreign body" reaction and maybe an allergic (hypersensitivity) reaction to foreigh protein. The question remains , are specific toxic substances also present?

Within the "trunk" supporting the spines are granulated cells (blobs in the pic below) which resemble human mast cells - the cells which contain allergic chemicals such as histamine.

The skin reaction caused by caterpillars is seen here http://medent.usyd.edu.au/photos/cupmo1.jpg


























The bubbly looking cells at left are fat cells responsible for energy storage. These are located beneath the skin - in sequence are the pimented layer and the bright pink cuticle with a pigmented spiny projection.





















http://www.mja.com.au/public/issues/173_11_041200/isbister/isbister.html#refbody1

http://www.austmus.gov.au/factsheets/cup_moths.htm

http://www.users.bigpond.com/gsbite/research.htm

http://www.insektus.com/page.php?id=2