Cotesia congregata

(Say, 1836)

Hornworm Parasitoid Wasp

Cotesia congregata is a gregarious endoparasitoid and a model organism in insect physiology research. Females oviposit into caterpillar , primarily tobacco hornworm (Manduca sexta) and tomato hornworm (Manduca quinquemaculata), simultaneously injecting a symbiotic (CcBV) and venom. The virus suppresses host immune defenses and disrupts development, allowing wasp larvae to complete their growth inside the living host. Mature larvae emerge through the host and spin white silk cocoons on the exterior surface. The wasp exhibits post- learning of host plant cues, with a critical learning window of 0–4 hours after emergence.

Cotesia congregata on Manduca sexta by Beatriz Moisset. Used under a CC BY-SA 4.0 license.The American Museum journal (c1900-(1918)) (18161617255) by Internet Archive Book Images. Used under a No restrictions license.Caterpillar with eggs1 by 8thstar (talk) (Uploads). Used under a CC BY-SA 3.0 license.

Pronunciation

How to pronounce Cotesia congregata: /kəˈtiːziə ˌkɑnɡrɪˈɡeɪtə/

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Identification

Distinguished from other Cotesia by association with Manduca hornworms and documented . Field identification relies on observing clusters of white silk cocoons on the surface of living or caterpillars. Distinguished from Cotesia flavipes (sugarcane borer ) by host range and geographic distribution. Distinguished from Cotesia vanessae by host preference for Noctuidae versus Sphingidae. Molecular identification possible through bracovirus sequences; CcBV has one of the largest known viral genomes (567,670 ) arranged in 30 circular segments.

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Habitat

Agricultural and natural environments where Solanaceae plants occur, including tobacco fields, tomato gardens, and areas with native nightshades. Associated with vegetation supporting caterpillar hosts in the Sphingidae and Noctuidae.

Distribution

North America (primary range), with records from the United States and Canada. GBIF records indicate presence in Middle America, Caribbean, and South America (Brazil), though these may represent related or misidentifications; iNaturalist treats C. congregata as a .

Seasonality

Activity coincides with availability of 2nd–3rd instar caterpillars. In temperate regions, multiple per year are possible; host caterpillars overwinter as pupae, and resumes with spring host availability. Laboratory studies indicate wasps live 4–8 days after emergence from cocoons.

Diet

feed on floral nectar and honeydew; larvae are obligate endoparasitoids feeding on and tissues. Adult feeding specifically observed on organic honey in laboratory conditions and implied from floral visitation .

Host Associations

Life Cycle

Females locate 2nd–3rd instar caterpillars and oviposit multiple while injecting and venom. Eggs hatch in host hemocoel within 2–3 days, releasing teratocytes that grow to visible size. Larvae undergo two within host over 12–16 days. Third instar larvae emerge through host and spin white silk cocoons on host exterior. eclipse from cocoons after 4–8 days. Not all larvae successfully emerge; some are encapsulated by recovering host immune system, while others exhibit reduced growth. Sex ratio highly female-biased (documented 277:3 in one ).

Behavior

Females exhibit rapid location and oviposition, delivering multiple stings with ovipositor upon encountering suitable hosts. Post- learning occurs in critical window of 0–4 hours after emergence; females exposed to host larvae on specific plants develop positive searching responses to those plants and inhibited responses to otherwise attractive plants. Learned plant associations persist 6–7 days. exploit herbivore-induced plant volatiles for host location. Parasitized hosts exhibit permanently reduced feeding and locomotion approximately 8 hours before wasp emergence, potentially preventing destruction of wasp cocoons.

Ecological Role

Important agent of lepidopteran pests, particularly hornworms damaging Solanaceae crops. of Manduca spp. in both agricultural and natural . Hyperparasitism documented: pupae may be attacked by chalcid wasps (Hypopteromalus, Conura sp.).

Human Relevance

Used as model organism in insect physiology, - interactions, and research. Significant natural enemy in home gardens and commercial tomato/tobacco production; presence indicated by white cocoons on hornworms. Not a stinging threat to humans—venom is host-specific and negligible effect on non-host organisms.

Similar Taxa

  • Cotesia flavipesBoth are gregarious braconid with ; distinguished by preference (Diatraea saccharalis, sugarcane borer vs. Manduca spp.) and distribution (tropical/subtropical vs. temperate North America)
  • Cotesia vanessaeBoth in Cotesia; distinguished by preference (Noctuidae vs. Sphingidae) and geographic range
  • Cotesia glomerataGregarious of Pieridae caterpillars; distinguished by and cocoon arrangement (tight cluster vs. scattered on host)

Misconceptions

White objects on backs are often misidentified as of the ; they are actually silk cocoons of emerged larvae. The is not an independent but an obligate integrated into , incapable of replication outside wasp calyx .

More Details

Polydnavirus Symbiosis

Cotesia congregata bracovirus (CcBV) has one of the largest known viral at 567,670 arranged in 30 circular segments. The virus cannot replicate independently; are produced in female calyx from genomic sequences. Viral gene products include protein tyrosine phosphatases (interfering with cytoskeleton dynamics), ankyrin repeat proteins (immune inhibition), cysteine-rich proteins (similar to teratocyte secretions), and cystatins ( inhibitors). Only 0.1 ng viral DNA injected per , but female produces >600 ng per ovary, sufficient for lifetime egg production averaging 1757 eggs.

Host Manipulation

Virus and teratocytes synergistically disrupt endocrine system: esterase activity reduced causing elevated JH titers, levels suppressed, blocked. Host reaches sixth instar with high loads, or parasites may emerge in fourth instar with low loads. Host immune suppression occurs within 24 hours of oviposition via apoptosis; partial recovery after 8–10 days, but larvae develop independent resistance by this point. Brain proteomic changes include altered synaptic transmission and antimicrobial upregulation correlating with bodyguard .

Genetic Differentiation

show genetic differentiation associated with -foodplant complexes, with documented asymmetric hybrid dysgenesis between populations from different host sources. Differential bracovirus observed among host-foodplant sources, likely reflecting adaptations to specific host and diets.

Spermatozoa

Possesses the shortest known flagellated spermatozoa in animals at 6.6 μm ( plus ), approximately 8,800 times shorter than the longest known (Drosophila bifurca).

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Sources and further reading