ON SOME ANIMAL PARASITES IN BRITISH GUIANA. 181 



Tabanidae, especially when feeding, can often easily be captured by carefully 

 placing over them a killing tube ; as soon as the fly finds itself imprisoned it will fly 

 up into the tube and the cork may then rapidly be inserted, or else the tube may be 

 held over the insect in situ while the cyanide does its work ; with a restive animal 

 however this is not always possible. 



A convenient-sized tube for this work is one about 8 cms. in length and 3 cms. in 

 diameter and of good quality thick glass. The cork should fit well, but not too 

 tightly, or trouble will he experienced in its withdrawal ; it should be well waxed 

 externally. 



Small pieces of cyanide mixed with a somewhat larger quantity of boracic acid 

 powder are placed in the bottom of the tube and rammed well down ; a thin layer of 

 cotton wool follows also well rammed down, and finally about 3 or 4 disks of thick 

 blotting paper, cut out slightly larger than the diameter of the tube so that they fit 

 tightly when pressed down and thus prevent the entire mass from shifting. The 

 boracic powder prevents the cyanide from dehquescing and also seems slightly to 

 stimulate its action. The whole mass should not occupy more than about 3 cms, 

 of the length of the tube. 



A further advantage of this method lies in the fact that when the cyanide becomes 

 exhausted it can easily be removed and the tube recharged ; anyone who has used 

 the plaster of Paris and cyanide method of charging killing bottles is familiar -with 

 the difficulties and inconveniences of recharging, especially in the damp atmosphere 

 of the tropics, which hastens the dehquescence of the cyanide. 



Ticks are easily collected by means of the forceps, though care should be taken 

 in removing them, so as not to leave the mouth-parts embedded in the cuticle of 

 the host. 



Lice are often hard to find, especially on birds, but experience will in time indicate 

 the most likely parts of the body on which to search. 



When examining poultry and other kinds of birds better results will be obtained 

 if a person is employed to hold the bird firmly in a convenient position while a careful 

 examination is being made. 



A pair of small but sharp scissors often prove useful for the entire removal of a 

 feather or feathers infested with lice. The specimens can afterwards be removed 

 in the laboratory with a certainty and exactness seldom possible under field 

 conditions. 



Parasitic Worms. 



Our investigations in connection with parasitic worms, carried out principally 

 among domestic animals, have revealed a highly interesting field of almost unlimited 

 scope. A curious feature is the comparative rarity of tapeworms among the ordinary 

 Creole dogs. We have never encountered them during our post mortem examinations 

 and only very rarely have the cast mature segments been observed. 



The determinations have in all cases been made by Mr. H. A. Baylis, Department of 

 Zoology, British Museum. Unfortunately, in some cases the specimens were not 

 sufficiently well preserved to allow of a certain identification. A number of other 

 worms have been collected from various hosts, but owing to the present European 

 conditions we have been unable to get them identified. 

 (C288) f2 



