6 LEAFLET 6 5, U. S. DEPARTMENT OF AGRICULTURE 



them consecutively, first a meat bait, then a fish bait, then a cereal 

 bait, then meat, and so on. In poultry pens it is best to expose the 

 baits in the feeding troughs while the chickens are shut up ; or the 

 baits may be exposed behind boxes or boards so leaned against the 

 wall to form a runway for rats that the chickens can not reach them. 

 Baits should be left out for three days, after which all those un- 

 eaten should be collected and destroyed. If any sign of live rats is 

 noted after one week, wait two additional weeks and then prebait for 

 several nights before exposing more red-squill bait. Prebaiting is 

 important if an unsuccessful effort has previously been made to de- 

 stroy rats. This consists of exposing fresh untreated foods prepared 

 in precisely the same way as the squill baits except that the squill is 

 omitted. These clean baits should be put out at 2-day intervals, 

 and all not consumed should be destroyed the morning following 

 their exposure until the suspicion of the rats has been overcome and 

 they take the baits freely. When this occurs, substitute the squill 

 baits, and a complete clean-up should result. 



Rats that have eaten a fatal dose of red squill usually become 

 lethargic, or dopey, within an hour or two, and from 4 to 14 hours 



later they exhibit characteristic tremors and depres- 

 Effect on sion in the hind legs. This condition is followed by 



Rats progressive paralysis of the trunk and forelegs, 



breathing becomes labored, and the animal starts to 

 roll over and over in a peculiar and extremely characteristic manner. 

 This rolling motion continues at intervals for half an hour, or pos- 

 sibly 24 hours, before death, depending upon the dose taken. Few 

 rats that show these symptoms recover. Post-mortem examinations 

 have indicated acute dilatation of the heart to be the probable cause 

 of death from red squill, although continuation of the heart beat in 

 many instances after breathing had stopped also indicated that 

 respiratory paralysis plays a part. Irritation of the digestive tract 

 also is pronounced, but not to an extent that would prove fatal. 



'^"nipv^^m iwi t 



* 









mm 



Figure 2. — Although rats poisoned with red squill usually die underground, 238 

 v/ere picked up on a Kansas farm after the baits were exposed 



