14 



In following the post-embryonal history of insects there is work for all. While allied 

 forms have in general a very similar development, there are so many which are unexpec- 

 tedly found to differ from one another, that every addition to our knowledge of the life 

 histories of insects is a gain, and they are to be praised who give their close attention to 

 this matter. Here is a field any Entomologist, even the most unskilled, may cultivate to 

 his advantage and with the assurance that every new history he works out is a distinct 

 addition to the science. The importance of an accumulation of facts in this field can hardly 

 be over-estimated, and those whose opportunities for field work are good, should especially 

 take this suggestion to heart. Nor, by any means, is the work confined to the mere 

 collection of facts. How to account for this extraordinary diversity of life and habits 

 among insects, and what its meaning may be, is one of the problems of the evolutionist. 

 There are also here some especially curious inquiries, to which Sir John Lubbock and 

 others have recently called attention, and to which, in this country, Mr. Riley has contri- 

 buted by his history of Epicauta and other Meloidce. I refer to the questions connected 

 with so-called hypermetamorphosis in insects. In these cases there are changes of form 

 during the larval period greater than exist between larva and pupa, or even between larva 

 and imago, in some insects. There are also slighter changes than these which very many 

 larvae undergo ; indeed, it may safely be asserted that the newly -hatched and the mature 

 larvae of all external feeders differ from each other in some important features. The 

 differences are really great (when compared to the differences between genera of the same 

 family at a similar time of life) in all lepidopterous larvae, as well as in all Orthoptera 

 which have come under my notice. No attempt to co-ordinate these differences, or to 

 study their meanings, or to show the nature of their evident relationship to hypermeta- 

 morphosis has ever been attempted. 



Not less inviting is the boundless region of investigation into the habits of insects 

 and their relation to their environment. The impulse given to these studies by the rise 

 of Darwinism, and the sudden and curious importance they have assumed in later investi- 

 gations into the origin and kinship of insects, need only to be mentioned to be acknow- 

 ledged at once by all of you. The variation in coloration and form exhibited by the same 

 insect at different seasons or in different stations, "sports," the phenomena of dimorphism, 

 and that world of differences between the sexes, bearing no direct relation to sexuality ; 

 mimicry also, phosphorescence and its relations to life, the odours of insects, the relation of 

 anthophilous insects to the colours and fructification of flowers, the modes of communication 

 between members of communities, the range and action of the senses,* language, commen- 

 salism — these are simply a few topics selected quite at random from hundreds which might 

 be suggested, in each of which new observations and comparative studies are urgently 

 demanded. 



The fundamental principles of the morphology of insects were laid down by Savigny 

 in some memorable memoirs more than sixty years ago ; the contributions of no single 

 author since that time have added so much to our knowledge, notwithstanding the aid 

 which embryology has been able to bring. Nevertheless there remain many unsolved 

 problems in insect morphology which by their nature are little likely to receive help from 

 this source. Let me mention three : 



The first concerns the structure of the organs of flight. The very nomenclature of 

 the veins shows the disgraceful condition of our philosophy of these parts ; the same termi- 

 nology is not employed in any two of the larger sub-orders of insects; names without 

 number have been proposed, rarely, however, by any author with a view to their applica- 

 bility to any group outside that which formed his special study ; and a tabular view which 

 should illustrate them all would be. a curious sight. A careful study of the main and 

 subordinate veins, their relations to each other, to the different regions of the wing, to the 

 supporting parts of the thorax and to the alar muscles, should be carried through the entire 

 order of insects ; by no means, either, neglecting their development in time, and possibly 

 deriving some assistance in working our homologies by the study of their hypodermic 

 development. 



* Notice Meyer's beautiful studies on the perception of sound by the mosquito. 



