SCIENTIFIC SURVEY. 



209 



stones, or among grass and weeds, when they may be taken with 

 the water net in great abundance, and are beautiful objects for 

 aquaria. The perfect insects should be preserved in alcohol for 

 study, as they shrivel up when pinned. They should be described 

 when alive if possible. 



Thysanura. — Spring-tails. These interesting, minute, wingless 

 forms, which seem to afford a passage into the Myriapods by the 

 uniform size of their iugs, which form a continuous series, from 

 their head to the extremity, without showing the usual divisions 

 into three divisions of the body, seem to be but a degraded form 

 of neuroptera by their resemblance to the larvae of Perla and 

 Ephemera ; for like them they have long antennae, distinct jaws 

 and maxillae, and also caudal setae or bristles on the terminal ring 

 of the body. Their limbs also strongly resemble those of Perla. 

 Moreover they undergo no metamorphosis, the larva gradually 

 assuming the adult form by successive changes of their skin. ■ The 

 species are found abundantly in moist, dark places, under sticks, 

 stones, among fallen leaves, or under bark of trees, while some 

 occur in great profusion about manure heaps and hot beds in early 

 spring. 



Podura. This genus is rather broad, the body is hairy ^^^- ^~- 

 with a few scales, antennae short and few jointed ; the 

 head is separate from the thorax, and the abdomen is 

 provided with setae converted into a forked tail bent 

 beneath the body, used for leaping to a great distance. ^7 

 They are found in gardens, hot beds, or leaping on the /^ 

 surface of the water in quiet pools. 



Lepisma, (Fig. 32,) is long, and covered with minute 

 silvery scales ; the antennae are rather short, and the 

 abdomen has three long bristles. The species run 

 rapidly and are found in old books, in woolen cloths 

 which they eat, in mould and under bark, &c. 



Arachnida. 



Spiders have no antennae. Their legs present seven distinct 

 joints, and the tarsi are two jointed. At the base of the mandibles 

 is a vesicle filled with poison, which can be poured into the tips of 

 the jaw, and thus poison the insects bitten by the spider. This 

 bite, except in rare instances, is harmless to man. " Scorpions 

 are viviparous. With the egg-laying spiders, the egg, under the 



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