No. 461] WORTH AMERICAN INVERTEBRATES. 297 
these are called chevrons. The legs may have longitudinal 
marks— stripes ; or transverse marks— bands. 
Spiders at birth are often very different from their later 
stages, so that it is impracticable to identify them by tables 
prepared for adults. However, many spiders when one or two 
months from maturity are sufficiently similar to their parents 
to be placed in the proper genus. None but specialists should 
attempt the specific identification of immature spiders. At 
maturity the female has her epigynum exposed, and the male has 
the complicated structures of the palpi uncovered. Spiders 
without these developments should not be studied by the begin- 
ner. There are a few forms of uncertain generic position 
which have not been included in the tables. They are rare, 
doubtless more so than various new generic forms that have not 
yet been collected, though occurring in our country. The spider 
fauna of many portions of the South and West has been only 
slightly explored, while a closer examination of our southern 
borderland will reveal various genera now known to occur in 
Central America only. Nevertheless the more common spiders 
in any portion of our country will be found in the following 
tables 
MYGALOMORPHA. 
Two pairs of lung-slits on venter of abdomen; fangs of mandibles 
moving vertically, parallel to each other. 
1. Legs very long and slender, femur I longer than body Hypochilidz. 
Legs short and heavy, femur I shorter than body . Theraphosid. 
ARACHNOMORPHA. 
But one pair of lung-slits on venter of abdomen; fangs of mandibles 
moving somewhat horizontally, toward each other. 
I. Without eyes ; small pale cave "e rn: Linyphiide. 
With six or eight eyes ^ qu d. 
2. With eight eyes ; “a 
With but six eyes . 
3. Alleyes close together upon a Landi bare or eminence ; large species, 
yellowish brown or brown in color San 
All eyes not situated upon a small meliin tubercle i 
4- Apex of abdomen surrounded by a circle of bent hairs ; sia eripi 
