I have always noticed that the pest roaches killed by roach spray start to break down much more slowly than a roach that was stomped or attack by a lizard. In those cases the roach's body attracts ants within an hour or two, and they leave the wings and antennas after a couple of hours or so.

But when I kill a roach with spray, there's no ants or flies. The antennas break after 24 hours but the body stays intact for at least a week, provided that the roach is kept in a clean and dry place but has access to air.

So, if there's no maggots or attracted insects because of the poison, the only decomposition happening is from the bacteria/protozoa inside the roach's body? And the cellular death? Absolutely nothing intruding from the outside?

  • $\begingroup$ You're wondering why if you kill an insect with an insecticide spray, why other insects don't attack the body for food? $\endgroup$
    – mgkrebbs
    Apr 30 at 20:30
  • $\begingroup$ @mgkrebbs No. I was wondering what's happening inside the body and in microscopic level because in non-poisonous cases ants or maggots do the job quickly in front of our eyes. Also, most poisoned roaches go to dustbin before I can get my hands on them, but right now I have a specimen lying on my floor for 7 days straight, visibly unaffected from outside. $\endgroup$
    – sp631996
    May 1 at 15:30

Features of a rotting insect carcass

What you see after an insect dies is its chitinous exoskeleton. It is a tough biomaterial that takes time to decompose, given its structure, and few microbes can digest it, let alone as quickly as soft tissue. It's a little bit like human bones. The insect's inner soft parts will degrade quickly, just as with any dead, soft tissue. However, what remains looks intact, because the outer cuticle is resistant to deformation; it keeps its shape!

Exoskeleton decomposition by insects

Ants are known to, and can and will break exoskeletons into pieces and carry it away in parts. They are ubiquitous and exist everywhere, so it's no surprise you see them doing this job all over the place. Flies and worms and mites may also feed on the softer parts and on the yeast or microbes that flourish in the decomposing tissue. It is also possible that some insects lay their eggs into the carcass, which would in some cases be a rich source of nutrition for the young insects, when they are in their larval stages (what you may confuse for worms).

Poison deters exoskeleton decomposition by other insects

If you introduce poison into the mix, obviously the roach carcass with be contaminated and its exoskeleton will remain relatively less likely to be touched by other insects, since it remains noxious to them. The effect on micro-organisms would be less pronounced, but that depends entirely on the contents, concentration, volatility and weatherablity of the insecticide that was used.


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