2 66 ARACHNOIDEA. 



CASE condition of being watched. But very often one sees reappearing 

 on the body of an insect which has been simply cleaned or 

 brushed, new Tyroglyphi which come from within or from the 

 cavities of the joints where they are apt to gather in large 

 numbers. This shews that the cleansing has been insufficient. 

 One can then have recourse to the heat of the stove or oven. 

 This proceeding is inconvenient when the insect turns out to 

 be what is technically called ** greasy." Besides, although the 

 Tyroglyphi may not resist the effect of a high temperature, the 

 eggs often do, especially when they are situated in the interior of 

 the body, and the mites swarm again soon after. 



We can scarcely recommend pure water, for if the outside of 

 the dirty insects is washed, it penetrates into the inside, leaving a 

 humidity unfavourable to the object in view. 



Alcohol is good for all the insects which can stand its action 

 without being hurt, in their colours, hairs or scales. It will not 

 do for Lepidoptera, but we have often placed beetles that are hard 

 and polished in a flask with a large mouth without taking the 

 trouble of cleaning them. The pin holding the insect is stuck 

 into the under-side of the cork, and the body soaks in alcohol 

 without going to the bottom of the vessel. An immersion of 

 several hours or a day is sufficient. Either simple alcohol, or 

 alcohol containing a small solution of corrosive sublimate, will 

 answer. After a bath of an hour in the latter, the insect should 

 be washed in pure alcohol to carry off the sublimate, which, with- 

 out this precaution, forms a whitish crust and corrodes the pins. 

 We prefer to use alcohol with arsenic or saturated with strychnine, 

 which, in ridding the insects from the Tyroglyphi, has the ad- 

 vantage of preserving them also against the Anthreni. 



Besides alcohol, there are liquids which scour the insects per- 

 fectly, killing the Acarids and carrying off their favourite aliment. 

 These very useful liquids are ether, benzine, essence of naphtha. 



Dr. Leconte has utilized the " atomiser" for thoroughly and 

 imperceptibly besprinkling the insects with such liquids. 



