Mesostenus sicarius
Townes, 1962
Mesostenus sicarius is a small ichneumon (6–13 mm) in the Cryptinae, described by Townes in 1962. The is closely associated with cacti in the (prickly-pear), where it parasitizes stem-boring or shoot-boring . Females possess a long, tail-like used to in concealed ; males lack this structure. The species has been documented in Colorado and Alberta, Canada.
Pronunciation
How to pronounce Mesostenus sicarius: /mɛˈsɒstɛnəs sɪˈkɛəriəs/
These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.
Identification
Distinguished from other Mesostenus by its close association with cacti and the specific it parasitizes. The bold black, , and red coloration is conspicuous among small . Females are readily separated from males by the presence of the long . Differentiation from other Mesostenus species requires examination of morphological details not described in available sources.
Images
Appearance
Small measuring 6–13 mm in length. Body boldly patterned in black, , and red. Females possess an elongated, tail-like extending from the tip. Males lack an ovipositor and have a more tapered abdominal terminus. long and multi-segmented, typical of .
Habitat
Strongly associated with prickly-pear cactus ( spp.) . Observed visiting sunflower in Colorado during drought conditions, though this appears to be facultative feeding rather than indicative of primary habitat.
Distribution
Documented from Colorado, USA and Lethbridge, Alberta, Canada. The Mesostenus contains ten in North America north of Mexico, with approximately four species occurring in Colorado.
Diet
have been observed feeding on extrafloral nectar secreted by sunflowers (Helianthus spp.). are that develop internally within .
Host Associations
- Acrobasis - Stem-boring or shoot-boring in the
- Opuntia - Prickly-pear cactus; primary association
Life Cycle
Females use the long to insert into concealed boring within cactus stems or shoots. develop as internal , eventually killing the host. Specific details of and are not documented.
Behavior
are persistent nectar foragers despite aggressive interference from defending sunflower . Constant movement and evasive when disturbed by ants makes observation and photography difficult.
Ecological Role
of stem-boring and shoot-boring , potentially contributing to of herbivorous in cactus . May incidentally visit flowers for nectar, though largely exclude from these resources.
Human Relevance
No direct economic importance documented. Like many , it may be underappreciated for its role in natural . The female is frequently mistaken for a by observers, causing unnecessary alarm.
Similar Taxa
- Mesostenus gracilisAlso occurs in Colorado and parasitizes concealed such as the Plum Borer (Euzophera semifuneralis); distinguished by associations and morphological details requiring expert examination
- Other Mesostenus speciesTen occur in North America north of Mexico; many are poorly known and require taxonomic expertise to distinguish
Misconceptions
The female is commonly mistaken for a venomous . It is not used for defense but for depositing in concealed .
More Details
Taxonomic History
Described by Townes in 1962. The was revised by Cushman in 1929, though this predates the description of M. sicarius.
Host Knowledge Gaps
associations are documented for only a few Mesostenus . Rearing from and related plants may yield new host records for this poorly known .