144 THE AMERICAN MIDLAND NATURALIST 



is just perceptibly smaller than the other two, and has also a num- 

 ber of teeth; but these are finer and fewer than in the other claws. 

 In addition to these claws there are also six accessory claws. 



The tip of the tarsus is usually armed with terminal tenant 

 hairs. These seem to be entirely wanting in the species for of all 

 the specimens examined by the writer, only one specimen showed 

 structures approximating this even remotely. 



The calamistrum is the hackle for the formation of the "hackle 

 band" characteristic of the web of this spider. It is composed of 

 several rows of curved spines on the upper margin of the meta- 

 tarsus of the hind legs. 



In the abdominal region, the following peculiarities are to be 

 noted: there is no pedical and no folium in the species. Muscle 

 impressions — small, hardened points indicating the place of attach- 

 ment of the muscles to the body wall — are present in M. Aurantia. 

 The dorsal surface seems to bear two pairs of muscle impressions, 

 while an unpaired one appears near the base of the abdomen. 



There are two kinds of spiracles in M. Aurantia. One kind is 

 the lung-slits; and there is at least one pair of these. The other 

 spiracles are the tracheal spiracles, situated in front of the spin- 

 nerets. Of these there is only one. 



The epigynum of M. Aurantia is a complicated organ. The 

 eiiitinous plate is depressed and furrowed longitudinally, and the 

 depressed area is divided by a ridge-like elevation which marks the 

 depression off into two furrows or channels, each leading into an 

 opening of the spermatheca of the corresponding side. 



There are four spinnerets having two segments each, and one, 

 the hind spinneret, having four segments. The sides of these organs 

 are firm, but the terminal portion, constituting the spinning field, 

 is membraneous. This latter portion is surrounded by two kinds of 

 hairs, simple and barbed. The number of spinning tubes is very 

 great — a hundred on each spinneret would probably be a conserva- 

 tive estimate. Aurantia spins silk of three colors. White silk forms 

 the web, the bands for securing captured prey, and the egg-cocoon ; 

 brown silk forms the interior of the egg-sac; yellow silk forms a 

 kind of buffer between the eggs and the outside covering. The 

 glands that secrete this silk are numerous and of several kinds. 

 The most numerous are the aciniform or berry-shaped glands. 

 Comstock has determined by experiment that the function of these 

 glands is the manufacture of the silk for the swathing band. The 



