same cement-like material, and the parent goes off, 

 perhaps to repeat the process elsewhere. The young 

 hatch with only three pairs of legs, but at each molt 

 they add new pairs on new segments, acquiring four 

 more legs at each molt. 



About 6500 different kinds of millipedes are 

 known. In the tropics, some reach a length of 8 

 inches and include dead insects and other bits of ani- 

 mal matter in their diet. In California, the millipede 

 Luminodesmus seqiioiae is luminous; its eggs are not. 



The Horseshoe "Crabs" 



(Class Merostomata) 



When Sir Walter Raleigh led his expedition to the 

 New World in 1584-1585, he fully expected to 

 encounter strange kinds of animal life. To help peo- 

 ple in the Old World become informed about any 

 unusual creatures, Sir Walter brought with him two 

 naturalists: Thomas Hariot, who would write accu- 

 rate accounts of whatever was encountered, and 

 John White, who would prepare watercolor draw- 

 ings. The reports of these men, published in Eng- 

 land in 1588 and 1590, made known for the first 

 time a very ancient type of life now familiar to many 

 people as horseshoe "crabs." 



Actually, the modern name is a corruption of a 

 very good description given in 1870 under the name 

 of the "horse-foot crab," for the main part of the 

 animal's body does have the form of a horse's foot — 

 not a horseshoe. Thomas Hariot used the Indian 



The horseshoe "crab" Limitlus pohjphemus, a living 

 fossil whose nearest kin today are scorpions and spi- 

 ders, breeds each spring in shallow waters. Females 

 deposit eggs in a beach near high-tide mark, and ac- 

 companying males deposit sperm on the eggs. (Flor- 

 ida. Allan Cniickshank: National Audubon) 



name "seekanauk," and remarked that "it is about a 

 foot wide, has a crusty tail, many legs, like a crab, 

 and its eyes are set in its back. It can be found in salt 

 water shallows or on the shore." 



John White added, in the caption to his drawing 

 showing these animals, that as the Indians "have 

 neither steel nor iron, they fasten the sharp, hollow 

 tail of a certain fish (something like a sea crab) to 

 reeds or to the end of a long rod, and with this point 

 they spear fish, both by day and by night." 



Horseshoe crabs run along the bottom with a 

 curious bobbing gait, or burrow shallowly in search 

 of a variety of food: seaweeds, young clams, dead 

 fish, marine worms. Or they swim inverted, some- 

 times to the surface of the sea. At the end of a swim- 

 ming bout, they may sink to the bottom and alight 

 upon their backs. The stiff, pointed tail is then used 

 as a lever in righting themselves. 



Seen from above, the horseshoe crab's body is 

 clearly armored but divided at a transverse hinge 

 into a larger forward part and a smaller hinder part. 

 The first bears the two large compound eyes and a 

 pair of smaller simple eyes, and the second ends in 

 the highly movable tail. The front portion of the 

 body is a shield covering the four pairs of walking 

 legs and two additional pairs of appendages asso- 

 ciated with the mouth. The mouth itself is an oval, 

 lengthwise opening between the leg bases. It gives 

 the class Merostomata its name from the fact that 

 the mouth extends over several segmental regions of 

 this portion of the body. 



Most members of class Merostomata are known 

 only from fossils. The class includes both the horse- 

 shoe crabs (order Xiphosura — "sword-tailed") and 

 the extinct eurypterids (order Eurypterida) or sea 

 scorpions. All of these animals seem strange in using 

 the spiny bases of the walking legs for chewing the 

 food, as though the animal's shoulders took the place 

 of jaws. 



Horseshoe crabs represent a style of life that has 

 existed in similar situations essentially unchanged for 

 at least 175 million years. All of the near relatives of 

 these creatures have been extinct for even longer, for 

 horseshoe crabs are not crabs at all. They are most 

 similar to modern land scorpions and spiders, and 

 quite unlike any of the crustaceans. 



From below it is easy to distinguish the sexes 

 among horseshoe crabs. In place of a pincer-tipped 

 chelicerae on each side in front of the mouth (as in 

 the female), the male has sturdy leglike appendages 

 ending in grotesque hooks. With this armament he 

 can cling to the rear of a female's shell for days or 

 weeks at a time and be towed along by her until she 

 is ready to deposit eggs. In both sexes the next pair 

 of appendages are the pedipalps, used in feeding. 



The hinder portion of the body has a triangular 

 outline and bears below it a series of overlapping 



