ARACIINIDA. MYRIOrODA. 49 



year, especially during the frosts of autumn, when the changes 

 produced are greatest. All spiders are directly beneficial to 

 agriculture by their carnivorous habits, as they all prey upon 

 insects, and do no harm to vegetation. Their instincts are 

 wonderful, and their habits and organization worthy of more 

 study than has yet been paid them. We have no species poi- 

 sonous to man, except when the state of health renders the 

 constitution open to receive injury from their bite, just as mos- 

 quitoes and black flies often cause serious harm to some per- 

 sons. 



The mites (Fig. 53, Nothrus) occur under bark, sticks, 

 stones, or on the bodies of birds and mammals or insects. 

 They should be preserved in alcohol. 



All kinds of Ticks (Ixodes, Fig. 54) should also be preserved 

 in spirits, as well as the minute species of mites which occur 

 everywhere. 



MYRIOPODA. 



CEHTIPEDS, THOUSAND LEGS, MILLEPEDS. 



The centipeds and millepeds (Fig. 55, Julus multistriatus) 

 live in damp situations under stones, sticks, leaves, Fig r)5 

 etc. They should be preserved in different stages of 

 growth in spirits. Several species (Spirostrephon) 

 live in caves and should be especially sought for. 



In conclusion we may say that while the Coleop- 

 tera, Lepidoptera, and Hymenoptera of the north- 

 eastern states of the union are comparatively well 

 known, specimens of all orders from the southern 

 and western states, the Pacific states, and the great 

 plains, however common, are eagerly desired, as well as 

 all cave insects. Specimens received by the Smith- 

 sonian Institution will be forwarded to experts for 

 identification and description. Specimens should 

 always be accompanied by small paper labels at- 

 tached to the pin or placed in the bottles. If writ! en 

 in pencil on heavy paper the marks will endure for a long time 

 Always state the locality and date of capture. 

 S. M. c. 2(31. 7 



