176 Specific Examples of Slide Making 



or indeed any other material from which small arthropods are customarily 

 collected. The only difficulty in using this equipment is in preventing the 

 heat from becoming too great. Some people use so large a lamp above 

 and so high a temperature around the edges that many small arthropods 

 are killed before they have time to fall into the trap laid for them. The 

 author has found that the water between the walls of the funnel for most 

 uses should be at a temperature of 30 to 40° C, and the lamp above should 

 under no circumstances raise the surface temperature of the material 

 above 60° C. These temperatures are for a moderately dry moss sample 

 and may be exceeded greatly when one is dealing with dry material, 

 such as straw. Wet moss of the sphagnum type, however, requires lower 

 temperatures if it is to be examined successfully. 



If permanent mounts are to be made for record purposes of all the 

 small invertebrates that may be found in the moss sample, it is necessary 

 to make adequate preparations to receive the animals while the moss is 

 being treated. Two kinds of gum mountants are desirable: (1) a high 

 refractive-index medium like Berlese's for the very heavy-walled forms, 

 such as the Oribatid mites and the pseudoscorpions and ( 2 ) a low refrac- 

 tive-index mountant like Gray and Wess's, for the thinner-walled forms, 

 such as the Tyroglyphid and Gamasid mites. This last medium is also 

 suitable for Thysanura and for Collembola. Thick-walled beetles and 

 fleas, if they are to be made into microscope slides, had better be treated 

 with alkali and should be accumulated for this purpose in a tube of 96 

 per cent alcohol. This process is described in detail in Gray's "Microt- 

 omist's Formulary and Guide." It consists usually of soaking the speci- 

 mens after rehydration in 10 per cent potassium hydroxide. Excessive 

 swelling may be controlled by enlarging the anus with a needle and by 

 putting holes in unimportant parts of the head and thorax. 



If one is dealing with a sphagnum moss, it is also possible that a num- 

 ber of crustaceans, particularly Cladocera and Ostracoda, are likely to be 

 found. These are better mounted in glycerin jelly in the manner also de- 

 scribed in Gray's "Microtomist's Formulary and Guide" and should be 

 transferred, as soon as they are found, to 30 per cent alcohol, where they 

 will die with their appendages extended. They should not be permitted 

 to remain in this weak alcohol for longer than is necessary to kill them. 

 Then they should be transferred to 96 per cent alcohol. A large number 

 of nematode worms are likely to turn up; these cannot be mounted by 

 any of the methods described in this book, and again reference should 

 be made to the author's larger work. A tube of some fixative, a supply 

 of clean 3- by 1-in. glass slides, and a number of coverslips should be 

 provided to receive any small annelids which may be found in the moss, 

 and which must be fixed, stained, and mounted at once. 



When all is ready and observation shows that no more forms are falling 



