Cooley & Kohls: Argasidae of N. America, etc. 



Dissections are made in a small, Syracuse watch glass (U.S. Bureau of 

 Plant Industry Model; diameter of 27 millimeters) under a microscope, with 

 the specimen immersed in alcohol. The watch glasses are improved if the 

 hottom is coated with collodion to prevent the dulling of sharp instruments. 



The hypostome is readily removed from adults and nymphs. The specimen 

 is carefully held in position with slender forceps. A transverse incision is made 

 a short distance posterior to the posthypostomal hairs with a very small, sharp, 

 iris scalpel; also two longitudinal ones, one on either side of the hypostome, 

 each starting at the point where the palpus meets the base of the hypostome. 

 This usually permits the removal of a part of the basis capituli with the 

 hypostome attached, 'but if not yet free, insert the iris knife horizontally 

 between the hypostome and the stalks of the chelicerae and cut through any 

 pieces of chitin still attached to the base of the hypostome. It is important 

 that this final incision be made with the point of the knife held horizontally 

 to insure that the hypostome will be flat when mounted in balsam and not 

 raised on one side. 



It is necessary to sharpen the scalpel frequently on a marble stone. This 

 is done under the microscope. For some dissections a blunt, rather than a 

 pointed, scalpel may be advantageously used. 



Care is needed to avoid losing dissected parts, hence the need for the very 

 small dishes. The parts to be mounted are readily transferred to the next 

 liquid by the use of a small brush of which most of the tapered portion has 

 been removed. 



In the study of the larvae it is sometimes necessary only to clear and 

 mount them if the specimens are unfed, but if critical studies are required 

 the more difficult manipulation of separating the hypostome from the chelic- 

 erae becomes necessary. This dissection can usually be accomplished best by 

 removing first only the chelicerae, leaving the hypostome and palpi in posi- 

 tion. This is often difficult and is usually best done with a fine needle point 

 and a sharp-pointed, iris scalpel. Finally, the entire capitulum is severed, 

 cleared in xylol and mounted in balsam with the venter up. 



Four percent potassium hydroxide is sometimes used as a clearing agent. 

 However, critical parts, particularly hypostomes, are sometimes obscured by 

 gas appearing within the specimen immediately after being placed in balsam. 

 This may happen even if preparation has included thorough washing to 

 remove the potassium hydroxide. It may be prevented by passing the specimen 

 through a series of xylcl-balsam mixtures of increasing density. The first should 

 be very fluid. This requires about twenty-four hours. 



Rearing. — It is sometimes difficult or impossible to identify immature 

 specimens, especially earily stage nymphs. If alive, such ticks can be reared 

 through one or more stages as desired, feeding being permitted as necessary. 



To facilitate holding living ticks in the laboratory for observation or 

 ecdysis various facilities have been used such as paper or wooden boxes held 

 over wet sand, test tubes with cotton plugs placed in covered jars, etc. The 



