12 MISC. PUB. 601, U. S. DEPT. OF AGRICULTURE 



emerge they will be attracted to the light, enter the vial, and can be 

 easily removed and killed. Tiny parasitic wasps may be reared from 

 their hosts in this manner. A cardboard ice-cream container is excel- 

 lent for this type of rearing. 



Adult moths, butterflies, beetles, and many other insects may be 

 obtained by collecting pupae and caging them until the specimens 

 emerge. In this way the best specimens of moths and butterflies may 

 be secured. Always permit the reared specimen to harden and color 

 completely before killing it, but do not leave it in the cage so long 

 that it will damage itself in trying to escape. Cages should always 

 be placed where they will be safe from ants. 



Very often bark and wood infested by boring insects, such as beetles, 

 are found. If these are placed in glass or metal containers, excellent 

 specimens of the adults may be obtained. Cages of wood and card- 

 board should be avoided for obvious reasons. Such material can often 

 be collected and caged during the winter months, the period of effec- 

 tive field collecting being thus extended. 



HOW TO KILL AND PRESERVE SPECIMENS 



The method of killing and preserving to be used depends upon the 

 kind of insects involved. No one method is satisfactory for all speci- 

 mens, and it is necessary for the collector to have some knowledge 

 of what is being collected in order properly to care for the material. 

 Frequently it is desirable to kill in liquid any specimens that will 

 later be pinned for the collection. The best general liquid killing 

 and preserving agent, which should always be used unless some other 

 preservative is especially recommended, is 70- to 75-percent grain 

 (ethyl) alcohol. Formalin, which is frequently used as a preserva- 

 tive for biological specimens, is not recommended as a preservative 

 for insects because it hardens the tissues and makes the specimens 

 difficult to prepare for study. In the discussion that follows, alcohol, 

 unless otherwise indicated, means 70- to 75 -percent grain alcohol. 



The procedure to be followed for all insects killed in alcohol but 

 later mounted dry is as follows : 



1. Kill in alcohol. 



2. Dehydrate in 100-percent alcohol (200 proof, also called absolute alcohol). 

 This step takes from 1 to 24 hours, depending on the size of the specimens. 



3. Degrease in xylene (zylol) or benzene (benzol). This step requires about 

 the same length of time as the dehydration. If specimens retain a milky film 

 in the xylene they have not been completely dehydrated. 



4. Remove from xylene, dry, and mount. 



Specimens killed in the ethyl acetate killing bottle, but which con- 

 tain considerable fatty tissue (lipoids), should be degreased before 

 being mounted. Any of a number of lipoid solvents may be used, the 

 most satisfactory of which is ordinary commercial sulfuric ether. 

 Soak the specimens in the ether bath until the fluid ceases to become 

 yellow from the dissolved oils, changing the fluid if necessary. The 

 length of time necessary for complete degreasing will vary from a 

 day to a week, depending upon the size and number of specimens, 

 their fat content, and the volume of ether used. A wad of absorbent 

 tissue or filter paper should be placed in the bottom of the container 



