Pomona CoLiiKOE Journal op Entomology 813 



III ;i iHinihcr <tl" otlior rMiiiilics of s|)i(lrrs cxaiiiiiicd tlicri' wcru no hairs 

 of unusual types. Tn a few tlicrc wcri' only a very frw plume-like setiE as in 

 the A^clenida' (A(iiIr)Hi vacvia), wliere there were only a very few hairs 

 like Figure 255. !). 



SetJB were also stmlied in examples of more liistaiitly related {groups of 

 arthropods. Fijiure 256, 10, 11 and 12, are from a young Limulus. A 

 rather usual type of hair is shown in 10. The tijis of some of the seta- have 

 lateral pro.jeetions such as shown in 11. A simple type witii its conimuni- 

 cation througli tlie eliitin is sliown in 12. 



Among the I'edipalpida, there are many hairs of the usual t.ype sucii as 

 Figure 25(), 1, but 2 shows a rather different structure where the hair pro.jects 

 from a little mound, and ^5 shows simjile eli-vations from whieh there are no 

 hairs pro.ieeting. 



Members of the Phalangida examined show rather usual types of hairs, 

 similar to 4 and 5, which were found on various parts of the l)ody of 

 Leohunum sp. 



Among the Solpugida no new t.vpes were encountered. 



The hairs of Aearina are both of the usual sort and also plume-like. 

 Berlese ('12) reeentl.y described many t.vpes of plume-like hairs in various 

 species. These seta' were chiefly from the bod.y. 



Tile hairs of the pseudoscorpions are of the usual t.vpc and so far as 

 studied no other kinds are present. 



Coming now to more distantly related groups we have Figure 256, 8 and 

 9, from a large diplopod. The first of these shows a hair of usual type with 

 its canal through the thick cuticle. The second of these figures shows a larger, 

 heavier hair located on a little mound with the base hollowed out but the 

 cavity very slight beyond this point. 



Figure 256, 10-14, shows simple hairs from a chilopod, Scolopenflra sp. 

 Some of the smallest of these are .just simple pro.jeetions from a .slight eleva- 

 tion, one is a minute hollow elevation. Some of these simple hairs show 

 stages in their development. 



Pa.ssing now to an,other group of arthropods we find in a member of the 

 Onyehophora, Pcripatus, very few hairs but numerous mound-like elevations 

 over the surfaces of the bod.y. Some of these little mounds are grouped to- 

 gether and from some of these true simple setae pro.iect ; as is .shown in Figure 

 256. 16. Some of the larger elevations have several setae, but most of the 

 mound-like elevations have none, and probably represent a very primitive 

 sensitive structure. 



Conclusions 



The hairs of tarantula are of two chief kinds, the usual simple sort and 

 the ]iluiiie-like structure. They are of many sizes from large and thick to 

 short and slender. All of these hollow hairs are undoubtedly sensory, hut the 

 great variations in form and structure are probably not altogether due to 

 special sensory functions and may be more for protection. Spiders with 



