White grubs came out of my caterpillar or chrysalis,
and have formed cocoons or pupae.
What is going on?
  
Don Herbison-Evans,
(donherbisonevans@outlook.com)
and
Stella Crossley


Anthela acuta caterpillar with red parasites.

Female moths lay between a hundred and several thousand eggs, depending on species. If all these matured and laid more eggs, then after several years the world would be covered in caterpillars.


Hyposidra talaca caterpillar with a parasite
(Photo: courtesy of Harold McQueen)

Their parasites and predators stop caterpillars in nature from taking over the world.


ants love pupae
(Photo: courtesy of Michael Watt, Cairns, Queensland)

The main parasites of caterpillars are particular species of viruses, bacteria, fungi, mites, ticks, wasps and flies.


Agrius convolvuli another caterpillar with a parasite: possibly a Sand Fly ( CERATOPOGONIDAE )
(Photo: courtesy of Diana Davey, Woolgoolga, New South Wales))

Caterpillars are just as susceptible to disease as we are, and get the equivalents of flu and measles etc. The viruses in the Cypovirus genus, and the bacterium Bacillus thuringiensis are especially fond of attacking caterpillars, and are used as a biological control agents against pest caterpillars.


Cryptoptila immersana caterpillar carrying green parasites
(Photo: Don Herbison-Evans, Sydney, New South Wales))

The exact relationship of the various species of Lepidoptera with the various parasitic species of mites (Acarina), flies (Diptera), and wasps (Hymenoptera) is often very specific, and is also of great importance in pest control.

Clania ignobilis
case opened to show pupa of parasitic fly
(Photo: copyright of Brett and Marie Smith, Ellura Sanctuary, South Australia)

If you should get some flies and/or wasps emerge from your caterpillar or pupa, you might consider donating them to your local natural history museum or university entomology department, who may have study programs on these parasites.


two Tachinid fly larvae recently emerged from a moth chrysalis,
one grub having already pupated.
(Photo: courtesy of Peter Street, Gosford, New South Wales)

The flies attacking caterpillars come mainly from the family TACHINIDAE.


dying Manulea replana, caterpillar with cocoons of a number of wasp parasites.

Wasps that attack caterpillars come from a variety of families, including:

  • BRACONIDAE
  • CHALCIDIDAE,
  • ENCYRTIDAE,
  • EULOPHIDAE,
  • EURYTOMIDAE,
  • ICHNEUMONIDAE,
  • PTEROMALIDAE, and
  • TRICHOGRAMMATIDAE,

  • wasp checking out a caterpillar
    (Photo: courtesy of Michael Watt, Cairns, Queensland)

    When a caterpillar is infected with a parasite, its behaviour changes, just as ours does when we get a cold or a fever. So though normally caterpillars will keep hidden, caterpillars when infected sometimes start wandering aimlessly about. So if you find a caterpillar wandering about, it is probably ill already.


    caterpillar with cocoons of a number of wasp parasites
    (Photo: courtesy of Jan MacDonald, Queensland)

    Predators also control the caterpillar populations,


    spiders hunt for caterpillars
    (Photo: courtesy of Kath Vail, Inner Pocket, New South Wales)

    such as spiders:


    Southern Old Lady Moth caterpillar (Dasypodia selenophora, NOCTUIDAE) vs Victorian Huntsman Spider (Isopedella victorialis, SPARASSIDAE)
    (Photo: courtesy of Wendy Moore, Melbourne)

    and adult wasps catch them to lay eggs on for their young to eat:


    wasps love caterpillars
    (Photo: courtesy of Trevor Jinks, North Burnett, Queensland)

    and various Bugs attack them,


    Caterpillar of Doratifera casta attacked by the Shield Bug Oechalia schellenbergii
    (Photo: courtesy of Jenny Holmes, Great Western, Victoria)

    and of course Praying Mantids will happily feed on any life stage of any Lepidoptera.

    Mantodea vs Lepidoptera
    Dingy Bush Brown butterfly (Mycalesis perseus, NYMPHALIDAE) vs Praying Mantis (MANTODEA)
    (Photo: courtesy of Jeevan Jose)

    Link to
    Frequently Asked Questions about Caterpillars

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    (updated 3 February 2013, 2 March 2017)