Chaetopsis

Loew, 1868

picture-winged flies, corn silk flies

Chaetopsis is a of ulidiid (: ) established by Loew in 1868. The genus includes at least 13 described distributed in tropical and semi-tropical regions of the Americas. Chaetopsis massyla is the most economically significant species, a major pest of fresh market sweet corn in Florida and tropical regions where feed on developing corn kernels and . The genus is characterized by picture-winged typical of Ulidiidae, with patterned and body form.

Chaetopsis massyla by (c) Bill Keim, some rights reserved (CC BY). Used under a CC-BY license.

Chaetopsis cf. massyla (Ulidiidae) - (female imago), Jefferson (NY), United States by

This image is created by user B. Schoenmakers at Observation.org, a global biodiversity recording project.
. Used under a CC BY 3.0 license.

Pronunciation

How to pronounce Chaetopsis: //kiːˈtɒpsɪs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Members of Chaetopsis possess the diagnostic features of : patterned or banded with distinct dark markings, and a relatively body with a somewhat elongated profile. -level identification within Chaetopsis requires examination of specific wing patterns, body coloration, and male . Chaetopsis massyla can be distinguished from the Euxesta eluta by behavioral responses to color: C. massyla is attracted to and green visual stimuli and avoids , whereas E. eluta is attracted to yellow and blue but not green. Electroretinogram studies show both species share similar spectral sensitivity peaks at UV (350 nm) and green (500–550 nm) wavelengths, but differ markedly in brightness-independent color discrimination .

Images

Habitat

Agricultural and natural in tropical and semi-tropical climates. Larval habitat is within developing corn ears (Zea mays), protected by husks, where they feed on kernels and . occurs in soil or substrate outside the cob, with depth influenced by soil and moisture—deepest pupation in muck soil at 10–50% field holding capacity, shallowest under dry or saturated conditions. Presence of structures simulating roots generally results in deeper pupation.

Distribution

Tropical and semi-tropical regions of North, Central, and South America. Documented in Florida (USA), Brazil, Argentina, and Sinaloa (Mexico).

Diet

feed on developing corn kernels and within corn cobs. Laboratory colonies maintained on corn kernel/agar diet supplemented with fresh green pepper sections.

Host Associations

Zea mays - larval sweet corn; primary economic
Capsicum - laboratory green pepper; used in laboratory rearing

Life Cycle

are laid on corn of developing cobs. hatch and feed on silk and kernels while protected within corn husks. Late larvae actively migrate out of cobs prior to , crawling or jumping to reach soil or substrate. Pupation occurs outside the cob, burrowed into soil or cardboard layers. Laboratory rearing at 27°C, 60–80% , and 16:8 light:dark yields living 10–14 days.

Behavior

Late exhibit active , leaving feeding substrate and crawling or jumping prior to . demonstrate strong attraction to and green visual stimuli independent of brightness, with avoidance of . This color discrimination behavior differs from Euxesta eluta despite similar underlying visual pigment physiology. Larvae burrow into substrate (cardboard or soil) for pupation.

Ecological Role

Major agricultural pest of fresh market sweet corn production, causing direct damage to developing kernels and facilitating secondary fungal establishment on damaged cobs. Untreated fields may experience up to 100% loss. Natural pupal include Spalangia spp. () with observed rates of 47%, as well as Muscidifurax raptor, M. raptorellus, Spalangia endius, S. cameroni, and . by Orius insidiosus () on and has been documented.

Human Relevance

Significant economic pest causing millions of dollars in losses to sweet corn production. Damage renders cobs unmarketable due to kernel feeding and secondary fungal . Management challenges include , difficulty targeting within protected corn husks, and alternate sources. Potential for using commercially available pupal (Muscidifurax and Spalangia ) originally developed for filth control.

Similar Taxa

Euxesta eluta congeneric corn pest with similar , use, and geographic distribution; distinguished by behavioral attraction to and (avoiding green) versus Chaetopsis massyla attraction to yellow and green (avoiding blue), despite similar spectral sensitivity physiology
Euxesta stigmatias corn pest in the same , co-occurring in Sinaloa, Mexico and Florida; part of the same pest complex causing similar damage to corn
Eumecosommyia nubilaThird member of the corn pest complex in Sinaloa, Mexico, with similar ecological role and damage

More Details

Visual Physiology

Electroretinogram studies of Chaetopsis massyla reveal spectral sensitivity curves with peaks in UV (350 nm) and green (500–550 nm) regions, best matched by visual pigments with maximum sensitivity at 350, 430, 500 and 560 nm in a 28:18:27:27 ratio. Despite this physiological similarity to Euxesta eluta, the two show markedly different behavioral responses to colored targets.

Pupal Biology

Pupal weight averages 4.24 mg in C. massyla. depth is significantly affected by substrate and moisture, with practical implications for management: shallow pupation under dry or saturated conditions may increase vulnerability to surface-applied treatments, while deeper pupation in muck soil at moderate moisture may protect from some control measures.

Species Diversity

The includes 13 described : C. aenea, C. angusta, C. apicalis, C. debilis, C. duplicata, C. fulvifrons, C. hendeli, C. laticauda, C. magna, C. massyla, C. mucronata, C. praeceps, and C. quadrifasciata. Detailed is documented primarily for C. massyla due to its economic importance.