Pomona College Journal of Entomology 811 



sensation, altliougli {)rol)al)ly servinK a very different purpose and stimulating 

 a (lifl'ei-eiit part of the nervous system, periiaps |)art oT liie sul)-liypoderiiuU 

 ner\i' piiwus known to oceur in many ar1iirn[)<i(is. These minute hair.s will 

 he eonsidered at this time only in so far as they may represent pai-1s of lioilow 

 .sensory seta\ 



One of the most noticeable features of tarantula is the f,'reat ahundanee 

 of lonj; hairs. These are esi)eeially numerous on tile legs an<l abdomen but 

 may be found on all parts. Two general types may be reeognized at once, 

 long rather large setre often brown or of a red color and short dark ones 

 often massed together and giving the appearance of black velvet. Hoth of 

 these are hollow and seem to be simply greatly modiiied hairs of the insect 

 type. The long brown or red hairs of tarantula are the most conspicuous. 

 Some of these are as long as .six mm. They are strongly chitinized, rather 

 slender, with a large cavity which is usually somewhat larger at the base. 

 Especially towards the tip, along the shaft, a fine pubescence is evident. In 

 Figure 255, 1, there is shown a hair of this type. Near the joints of the leg 

 there are fewer shorter, heavier hairs, almost spines, such as shown in Figure 

 255, 2. Between the long and heavier hairs of the legs and body there are 

 numerous fine sette which are quite plume-like because of the numerous 

 fine chitinous branches extending off from the shafts of the hairs. 

 Such a one is shown in Figure 255, 3, while Figure 255, 4, is a smaller one 

 from a leg. It is these setiE or hairs similar to them, that cause the legs and 

 body to appear dark. Modifications of this same type are found densely 

 mas.sed on the feet or other extremities where the dark velvet appearance is 

 most marked. These hairs are often enlarged or flattened at the tip. Figure 

 255, 5, 6 and 7, are of this sort. 



Near the mouth there are a number of long and short rather red hairs 

 with very little pubescence upon them. A small one of these is shown in 

 Figure 255, 8. Some of these red hairs about the mouth are nuieh like the 

 usual type, but many are long, slender and in some cases flattened somewhat. 



Comparison was made between the setae of tarantula and other spiders 

 from a number of different families. In all, the usual type of seta was found, 

 and the plume-like hairs, although less abundant, were found in almost every 

 representative. Figure 256, 1 and 2, are from one of the Lycosida?. The 

 first figure was taken from the back of the abdomen and was much like some 

 of those of tarantula, but was not so abundant. The second was a large hair 

 of the simple type from a leg. 



Figure 255, 3, 4 and 5, are from the Epeiridaj, Epcira gcmmn; 4 from the 

 caudal end of the abdomen is a simi)le hair with a high base. 



Figure 255, 6, 7 and 8, are from the ThomisidsE {Thanatus sp.) where, 

 in addition to the usual type of simple hair there are at least these three sorts 

 of setaj with side projections; 6, from the abdomen, is a short plumed hair 

 with thicker projections also; 7 is a short plumed hair; 8 is a seta with sec- 

 ondary projections on one side. This last sort is very abundant on the legs. 



