Cooke: On Scarcity and Abundance in Insect Life. 197 



germinate on healthy plants, by sowing them npoii the leaves, watering 

 the roots with water containing spores, and in other w^ays ; and also 

 whether yJants nmy be similarly affected by spores of other Mcld'ia, 



Mr. Thomas Hick, Harrogate, president of the botanical section, 

 will be glad to receive communications on the subject from those who 

 are disposed to assist in the work of investigation. 



ON SCARCITY AND ABUNDANCE IN INSECT LIFE. ' 

 {Concludtd.) 



By Beinv. Cooke. 



It remains now to indicate what steps should be taken in order 

 better to understand the causes of scarcity and of unusual abundance. 

 A series of meteorological observations for a number of years w-ill be a 

 considerable help ; and a careful noting of the results which follow 

 after an unusual continuance of heavy rains, and also of very dry 

 weather ; the effects of thunder-storms and of high winds, and of 

 great heat, provided it lasts for many days. Do not understand me to 

 assume that such observations have been neglected; this is not the 

 case, but they have not been carried out systematically and sufficiently. 

 The subject is, as yet, far from being within our grasp. 



We have now jirrived at the closing days of Febi'uary, and so far 

 have had a very exceptional winter. I believe it is 48 years since we 

 had a winter which can be compared with it for mildness. I will not 

 venture to predict what will follow, except, what indeed has already 

 begun to manifest itself, that many species of lepidoptera will appear 

 much before their usual time, and that if we have a favourable season, 

 we shall hear of some double broods which are not usual in this 

 country. How^ever, I hope we shall sec and take notice of anything 

 unusual which may fairly be attributed to the niildness of the winter. 



The theory that no species of insect is absolutely scarce, derives 

 considerable support from the fact that, previous to the last twenty 

 years, the larvae of many common species of lepidoptera were 

 unknown ; this therefore affords good reason for doubting whether 

 many species usually considered rare are so in reality. On the other 

 hand, it cannot be denied that among insects whose habits w^e know 

 very well, some species are very much more common than others, 

 consequently, if there is comparative scarcity, there is reason to believe 

 in absolute scarcity, at least \\\ some cases. In McLachlan's monogra};]! 

 of the British Neuroptera-planipennia, there is an insect described and 



