438 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XV. 



ledge. Still, this is a bye patb, a difficult piece of research that can more 

 profitably be taken up when the less difficult work is done and which 

 might, after all, yield no practical results. For some time to come we 

 can neglect these difficult problems with the satisfactory feeling that 

 they do not immediately concern us. Equally I leave on one side 

 all those problems concerned with colour and form, with Mimicry, 

 Warning and Protective Colouration, Natural Selection, the Inheritance 

 of Acquired Characters, etc. ; such subjects are full of interest, but it does 

 not assist us to know whether protectively coloured forms have become 

 so by natural selection and the survival of the fittest, or by directer 

 means. This is a subject worthy of the attention of this Society, but they 

 do not immadiately influence the problem of controlling injurious insects. 



E. — Insects and Plants. 



Lastly we may group together under one head all those questions that 

 arise in connection with the food of insects, for us especially the plants 

 they feed on. We are here concerned as much with botany as entomo- 

 logy. To commence with the simplest facts, we are still ignorant of what 

 insects will feed on even our common plants ; there is a good deal of 

 scattered information, notably in " Indian Museum Notes," and I find 

 a list of 150 species can be made up from that publication which are known 

 to attack particular plants, mostly crops. With the help also of the 

 various reports and other Government publications, and of the volumes 

 on Lepidoptera, etc., a fair basis can be made of the bare facts. 



When we look deeper into the question, again we find nothing definite 

 on record. We still have no idea of what governs an insect's choice of 

 food plants, whether the food plants vary with the seasons, why some 

 species have a large range of food plants, whilst others are limited to one or 

 two. This is important in all plant-feeding insects, but especially in the 

 sucking insects, Coccidce, Aphides, etc. 



On the botanical side we touch a very large subject in the means 

 of protection adopted by plants against insects, in the relation between 

 vitality and disease, and in the question of immunity from certain forms 

 of insect attack. I may refer you to a suggestive paper in this Journal 

 (Vol. II, No. 4, p. 232,) by Dr. D. Dymock, entitled " The Means of 

 Self-Protection Possessed by Plants." These problems are largely bota- 

 nical, and since botany is not swamped by systematic work, we need 

 not look in vain for information. But we do surely need actual lists 



