64 Annals Entomological Society of America [Vol.11, 



toward the same end. Two of these are worthy of mention. 

 They are: The accessory branch of the cymbium found in the 

 Linyphiinae and Tetragnathinae, sub-famihes of the family 

 Argiopidae, (figs. 6 a. b.), and the expanded patella of the Theri- 

 diidae (fig. 7 p). Both of these structures serve to overlie and 

 protect the base of the bulb. 



To conclude: The more complex palpi found in the Dip- 

 neumones have been developed by modification of a palpus 

 similar to that of fig. i . and the principal factor in their evolution 

 has apparently been that of protection from mechanical injury. 



EXPLANATION OF PLATE XIH. 



Fig 

 Fig 

 Fig 

 Fig 

 Fig 

 Fig 

 Fig 



1. Diagram of cp palpus of the most simplified form. 



2. o* palpus of Misumena, slightly digrammatic. 



3. (J' palpus of Phurolithus, from camera drawings. 



4. (J* palpus of Araneus, schematic. 



5. c? palpus of Lycosa, also schematised. 



6. (J' palpus of Erigone autumnajis, from a camera sketch. 



7. c? palpus of Lithyphantes corollatus, also from a camera sketch. 

 The strongly chitinized portions of the palpus are represented in heavy 



outline, the membraneous portions, including the haematodocha, in lighter out- 

 line. The semeniferous canal is represented by dotted outlines, the principal 

 axis, in each case, by an arrow. The morphological ventral side is turned up- 

 w^ard. 



a, alveokis; a. b., accessory Jjranch; b, bulb; c, cymbium; //, haematodocha; 

 p, patella. 



