Because (1) they evolved on land -- no gills, wings that are no use underwater, whole medium transfer ahead of them -- and (2) crustaceans appear in the fossil record about when trilobites do, way earlier than insects evolved, and they, being kickass creatures, have occupied the oceanic arthropod niches.
So I guess the question I should be asking is "why haven't the crustaceans taken over the land?", which they have in fact done a reasonable job at.
Interestingly, some people think that wings came from ancestral gills at some point along the line.
We have isolated crustacean homologues of two genes that have wing-specific functions in insects, pdm (nubbin) and apterous. Their expression patterns support the hypothesis that insect wings evolved from gill-like appendages that were already present in the aquatic ancestors of both crustaceans and insects.
I can't think of any insects that I know stay underwater, without coming up for air. Oh, hellgrammites I think. Other larvae? Not mosquito.
![[identity profile]](https://www.dreamwidth.org/img/silk/identity/openid.png){kind=small}
![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png)
timeasmymeasure
literal answer
Date: 2005-08-02 05:54 am (UTC)Re: literal answer
Date: 2005-08-02 07:33 pm (UTC)Interestingly, some people think that wings came from ancestral gills at some point along the line.
I can't think of any insects that I know stay underwater, without coming up for air. Oh, hellgrammites I think. Other larvae? Not mosquito.