INTRODUCTORY. 



of that in other insects. Many have been the con- 

 jectures why the insect races are thus liberally, in- 

 deed to all appearance lavishly, supplied with visual 

 organs. We shall detail their nature and probable 

 operation further on ; but ma/ hfere observe, that, so 

 far as we are able to judge, they are the best adapted 

 to the habits of the insect ; and that the end required, 

 namely the conveyance to the brain of a distinct 

 image of surrounding objects, could not have been so 

 effectually attained by any other contrivance. 



We trust that these brief allusions to a few of the 

 most striking phenomena connected with the exter- 

 nal structure of the worm and the fly, may have 

 awakened in your miud some curiosity to know more 

 of these household forms ; or wiU at least have satisfied 

 you that they are wonderftdly constructed for wise 

 and good purposes ; and we hope that you may now 

 be induced to pass on with us to a nearer consider- 

 ation of their structure and habits. 



We shall endeavour, as concisely as possible, and 

 so far as it lies in our power, to make you acquainted 

 with the present state of knowledge regarding their 

 natural history; but, as a great deal that relates to 

 their various organs has still to be elucidated, we 

 shall append, in notes, the names of the various 

 authors who have devoted their attention to the sub- 

 ject, and of such of their works as we have employed 

 as reference, iu order that you may, if so inclined, 

 avail yourself of these pages merely as a guide to a 

 more comprehensive view of the subject. 



