As every schoolchild knows, the presence of hair/fur is one of the defining characteristics of mammals. However, some bees and spiders etc. also have a fuzzy tegument. What makes bee fur different from mammal fur?
"bee fur" is very different from mammalian fur - they just happen look a bit alike. Bee fur is made of chitin whilst the mammalian equivalent is made of keratin. For bees it is primarily a way of trapping and carrying pollen whilst for mammals it is for thermoregulation and sensation.
Last edited by David Wynick (2nd Apr 2008 07:10:36)
Just to add a little more (and at a slight tangent…), the 'hairs' (setals) on inverts are, as David says, made of chitin extruded from the cuticle (the hard chitinous layer of arthropods - the exoskelton). For bees and particularly, bumblebees, these are modified in various places on the body. Using David’s example, in the 17 extant British bumblebee species, the hairs on the tibia of social females form the corbicula (pollen basket). On males (non-workers), these hairs are much reduced, as they are in the 6 cuckoo bumblebee species (ex of the genus Psithyrus but now included with the social bees as Bombus) that are inquilines (or social parasites, it seems to depend on the species) into the nests of social bees. The body hairs are coloured and may be utilised for Müllerian mimicry between all of the species (as well as bee mimics). The dense covering of body hairs on the bumblebees in particular may also have thermoregulation effects in terms of storing heat generated through the activity of the flight muscles.
For spiders (and many other arthropods, the size, structure and location of setals can be very useful in identifying species, particularly in carabids - the ground beetles), the setals are modified into spines, bristles, hairs and trichobothria, each differentiated by its thickness (spine being the thickest). These structures are important in many ways. For example, the bristles on the dorsal edge of metatarsus IV form the calamistrum, which is used to comb out a viscid substance from the cribellum (posterior to the spinnerets) which, when combined with ordinary threads forms a composite and adhesive lace-like strand of faintly bluish colour). Other setals are used for motion detection and some are used for defence (when tropical tarantulas brush their abdomens to release lots of barbed spines into the face of would be predators or careless zoologists).
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