58 MUSTARD. [1900 



wind-borne from some other country. The attack, or at least the 

 presence of this species, is to be found all over the Northern Hemi- 

 sphere, from Greenland to Abyssinia, and all interested in the subject 

 are well acquainted with the memorable migration of vast hordes of 

 this /'. (lai)niia across Europe in 1879. In this case the swarms left 

 North Africa in April, and, passing by way of Spain and Italy, traversed 

 Europe, doing serious injury by the caterpillar devastations they gave 

 rise to in their transit, and reached our shores early in June. 



From the notes sent me of the attack of the past season, there 

 does not seem to have been observation of previous presence of the 

 moths, and the coincidence of date of appearance of the attack in its 

 different stages, on the ttro different kinds of crop in the two localities, is 

 notexcarthj. The beginning of the caterpillar mischief must have 

 occurred at about the same date, and, from the specimens of pupae 

 in their cocoons sent to myself, the first moths emerged with only a 

 difference in date of one or two days. 



Measures of prevention and remedy seem hardly worth entering on, 

 as the attack is one that rarely occurs to an amount to cause serious 

 damage. 



On the face of the thing it might be supposed that spraying with 

 some good insecticide might clear the pests ; but amongst Messrs. 

 Coleman's notes it is mentioned that the Potatoes especially under 

 observation were sprayed, after the appearance of the caterpillar, with 

 a mixture of soft-soap and paraffin, but without effect. 



One of the more poisonous insecticides would, of course, be surer 

 in its effects on the caterpillars, but its use, at least on the Potato 

 leafage, might be objected to. 



Where the attack is on a small scale, as in gardens, hand-picking 

 the larvfe would be a sure way of abating the nuisance ; and with 

 regard to the chrysalids contained in the very observable cocoons, 

 where these are in the vast numbers sometimes observed in localities 

 where attack has been severe, it could not fail to be of use to have 

 these collected and destroyed ; but, so far as I am aware, beyond 

 desirableness of checking caterpillar attack whilst in progress, there is 

 no reason to take trouble, or go to expense, to prevent a following 

 year's recurrence of mischief. 



