a little vague. This is going to be the first image in a series.

Are you saying there is a mantispid inside this ball of silk or web or whatever? Is this a mantispid coccoon we're looking at? Do all neuropterans spin coccoons? What is the implication, that a mantispid larva ate its way into the spider eggs, gobbled up all the spider eggs, then spun its own cocoon? If these question seem dumb, well, consider their source :-)

hoped the info page would have had what you were looking for.
Yes, the the larva is inside the ball, or cocoon I guess. I don't know if all neuropterans spin cocoons.
Basically, the first instar mantidfly is free roaming. If lucky, it will cross paths with an unsuspecting spider host.

Some mantidfly spp. are known to feed off the spiders pedical as seen in image until the spider is ready to lay eggs. When the spider begins to construct an egg sac, the mantidfly moves in before the egg sac is completed. Safely concealed in the egg sac, the feast begins.
So far, all the larvae I found were around this stage.

Also, this series is cancelled. The mantidfly hatched and escaped. I had misplaced the container and left it open. However, the P. mira mantidfly series is about to begin.

Thanks for educating me about this, Jeff. The world of the arthropod is fraught with danger from every direction. How spoiled we are as a species.

take a look at the introduction here on the the first page. There are much more informative and accurate answers to your questions.

Mantispids are indeed as weird as they look.