PRESERVATION OF SLUGS 



By Leslie Hubricht 



Reprinted from The Nautilus, Vol. 64, No. 3, January, 1951 



The old method of kilHng skigs by drowning in a container filled with 

 water i.s un.satisfactory because the slugs struggle and secrete large quantities 

 of slime. The resultant specimens are not fully expanded and slime obscures 

 the color pattern. 



In the genus Philomycus there are a number of apparently distinct 

 color patterns which seem to have definite geographical ranges. But when 

 specimens are preserved these patterns are obscured by contraction and 

 slime so that their distinctness is lost. I realized that if the genus Philo- 

 mycus was to be understood, a better method of preservation would have 

 to be found. After trying a number of methods I found that the following 

 procedure would produce satisfactory results. 



Fill a tight container with water and add enough Chloretone to insure 

 a saturated solution and let stand for several days to dissolve. When killing 

 slugs some of this solution is poured off into a jar and enough water added 

 to cut the strength to 5 to 10 percent. It is not necessary to fill the jar as 

 the slugs will not struggle or climb out, but in a few minutes become 

 relaxed and extend themselves. Killing requires from 3 to 10 hours depend- 

 ing on temperature. When they are dead, which can be tested by pinching 

 the tentacles with a pair of forceps, if there is no reaction they are ready 

 for fixing. For fixing add enough 40 percent formaldehyde to make a 

 solution of one part of the formaldehyde to 16 parts of water and leave for 

 from 24 to 48 hours. After fixing they should be removed to 74 percent 

 alcohol for preservation. 



When this method is used the slugs are preserved life size with the 

 color patterns clear, and there is no fermentation of the stomach contents 

 which sometimes happens with the old method. Although the killing is 

 hastened by warmth, care should be taken to prevent overheating. The 

 heat produced by parking a car in the sun will ruin the specimens if they 

 are left inside. Wrapping the jar in a wet towel and placing it where the 

 air can get to it will prevent loss of specimens in warm weather. 



When to Collect Slugs. My best collections of slugs have been made in 

 rainy weather. I remember collecting large suites of Philomycus from tree 

 trunks, as far up as 5 feet from the ground, in Quebec hardwood forests. 

 On a geological field trip during which we were caught in a steady rain. 

 I have seen Philomycus crawling about on wet, bare rock in a situation 

 which I would have thought most unfavorable for them. This was an 

 exposure of Black Hand conglomerate, containing little calcium carbonate, 

 and with no vegetation cover whatsoever. The slugs were numerous, about 

 one to every square yard, and I pre-^ume that they took refuge in the cracks 

 of the rock during dry weather. Had I not seen this locality in the rain, 

 I would never have suspected that slugs were present. I therefore heartily 



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