As stated in the title, I'm looking for a book I read mid eighties in the UK.. however I have a feeling it was a few years old when I checked it out of local library, I can't recall the cover or much else in the checklist in this site.
The key points I recall are the large number people on a colony world have had to do an emergency move into a vast cavern system, possibly a meteor shower (or an invasion perhaps?)
They are trying to organise as disasters are happening all around them. This is due to infestations of the planets fearsome fauna.
The creatures have the ability to render themselves non-corpreal so they can't be touched. They are dropping onto people and wrapping their 'limbs' around them and then nuzzling at the back of their necks to feast on blood.
One bit I recall is a army general bellowing orders and rounding up his officers for a quick planning meeting, as he dashes through the milling mob he makes eye contact with a lad aged about fourteen who has a look of doomed horror.
There is a creature on the boy's back that is happily slurping and grunting at his neck. At the same time it's enthusiastically anally raping him continuously and can't be removed .
The army guy estimates, I think from his soldiers early colonial encounters with such creatures, that the hapless teen will be dead within three days.
I've looked through the guide on asking a good question but can't drag anything else up, however the scene I describe is pretty memorable so if you've read the book you'll recognise it. Thanks