376 Special Procedures 11 (chap. 23) 



ARTHROPODA. 



Insects and arachnids. Fiher, chloroform or potassium cyanide are 

 used for killing. Simplest method: Place a wad of cotton in the bottom 

 of a wide mouthed jar and cover the cotton ^vith a piece of wire screen. 

 Dampen the cotton with ether or chloroform or lay a few lumps of 

 potassium cyanide on it before adding the screen wire. Keep tightly 

 closed with a cork or screw cap. A piece of rubber tubing soaked in 

 chloroform until it swells and placed under the screen wire will hold 

 chloroform for several days. If the appendages should be spread when 

 fixed, as soon as the insect is dead place it on a glass slide with another 

 slide on top of it. Run fixative in between slides. 



For ivhole organisms, rapidly penetrating fixatives should be used: 

 picro-sulfuric, sublimate fixatives, mixtures containing nitric acid (Car- 

 noy), alcoholic and ordinary Bouin's, or Sinha's (1953) fixative. 



For whole mounts, the clearing of the exoskeleton is sometimes diffi- 

 cult. Body contents have to be made transparent, or sometimes have to 

 be removed. Lactophenol (page 121) mounting will serve the purpose 

 in the first case, but heavily pigmented arthropods probably will have 

 to be bleached in hydrogen peroxide for 12 hours or longer. Fleas, ticks 

 and the like make better demonstrations if not engorged; in any case 

 they should be treated with 10% potassium hydroxide, 8-12 hours, to 

 swell and dissolve the soft tissues, thus clearing out the body contents. 

 Wash well to remove the potassium hydroxide. Acid corrosives are 

 preferred by some because they do not soften the integument as much 

 as alkaline corrosives. 



Acid corrosive: 



glacial acetic acid 1.0 ml. 



chloral hydrate 1.0 gm. 



water 1.0 ml. 



Do not use a fixative containing alcohol or formalin if a corrosive is 

 necessary. The organism will not clear. 



For methods of mounting whole moimts, see page 378. 



Because of chitin, sectioning of insects can be difficult. Avoid higher 

 ethyl alcohols. Dioxane methods (page 39), butyl alcohol (above), or 

 double embedding (page 83) must be used and will provide excellent 

 results. Soaking the tissue blocks overnight or for several days in water 

 (page 55) will simplify sectioning. 



MOLLUSCA. 



Snails. Place in boiled water until limp. Fix. 



Mussels. Sections of undecalcified shell can be inade by grinding. 



