INSECTICIDES AXD EQUIPMENT FOR CONTROLLING INSECTS 19 



Caution. — Mercuric chloride is a violent poison and must be 

 stored in plainly labeled containers which are marked "Poison." 

 It reacts with metals; and solutions should, therefore, be placed 

 in wooden, earthenware, or glass containers. It is advisable to 

 wear rubber gloves when working with this compound. 



MERCUROUS CHLORIDE 



Mercurous chloride (HgCl) is known also as calomel. It is a white 

 powder insoluble in water. 



Suspensions or mixtures of calomel in water are employed for the 

 control of the cabbage maggot and the onion maggot, 3 or 4 ounces 

 being used in 10 gallons of water. One ounce of gum arabic is gener- 

 ally added to 10 gallons of the mixture to keep the calomel from 

 settling rapidly. The use of this material for the control of these 

 maggots is preferable in some cases to the use of corrosive sublimate 

 because of the highly toxic nature of the latter to man and animal-. 



Caution. — Mercurous chloride is not generally regarded as dan- 

 gerously poisonous, being commonly used, in small doses, as a 

 purgative. However, it should be stored in labeled containers out 

 of the reach of children and irresponsible persons, since excessive 

 doses are poisonous. 



METALDEHYDE (SLUG BAIT) 



Chemically, metaldehyde is a polymer of acetaldelryde. namely 

 (C 2 H 4 0)n, and only recently has been manufactured in this country. 

 It is available as a white powder which is insoluble in water but soluble 

 in benzene and chloroform. The technical grade is available in tablet 

 form. 



Metaldehyde is very attractive to slugs and snails and is used in the 

 bait form for these pests. It is prepared as follows : 



Metaldehyde 1 ounce. 



Bran or bread crumbs 3% pounds. 



To prepare the bait, mix the metaldehyde and the bran or bread 

 crumbs and store the bait in a jar or other container until needed. 

 When ready to use the material, place a portion of it in a pan and add 

 water slowly, while stirring it, until the bait is moistened, yet remains 

 crumbly when a handful is squeezed together. 



At dusk this moistened bait is scattered over the beds that are infested 

 with slugs, as described for applying poisoned-bran mash (p. 

 The treatment may be repeated in 2 or 3 weeks if the snails reappear, 

 or if their injury and slimy trails are discovered. 



After having eaten baits containing metaldehyde, the sings are 

 stupefied and finally die. Where the vegetation is dense and humidity 

 is high, the affected snails are killed more slowly or they may recover. 

 Under such conditions the following bait containing calcium arsenate 

 is more effective and kills more rapidly than baits containing only 

 metaldehyde: 



For small quantities For large qntmtitie* 



Calcium arsenate . 1 ounce. 1 pound. 



Metaldehyde '•_• ounce. '•_• pound. 



Bran 1 pound. 16 pounds. 



Molasses 2 teaspoonfuls l pint 



Water 1 pint. 2 gallons. 



