Macrosaccus

Davis & De Prins, 2011

Species Guides

5

Macrosaccus is a of leaf-mining in the Gracillariidae, established by Davis & De Prins in 2011. The genus currently contains six recognized , all of which are leaf miners on Fabaceae (legume family) plants. The generic name derives from Greek μακρο- (long) and σάκκος (bag), referring to the elongate saccus in male genitalia. Several species have become economically significant as agricultural pests, particularly M. morrisella, which recently expanded from native forest legumes to soybean.

Macrosaccus robiniella by (c) Mario Bassini, some rights reserved (CC BY), uploaded by Mario Bassini. Used under a CC-BY license.Macrosaccus robiniella by (c) Even Dankowicz, some rights reserved (CC BY), uploaded by Even Dankowicz. Used under a CC-BY license.Macrosaccus robiniella by (c) Mario Bassini, some rights reserved (CC BY), uploaded by Mario Bassini. Used under a CC-BY license.

Pronunciation

How to pronounce Macrosaccus: /ˌmæ.kroʊˈsækəs/

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Identification

The is distinguished from related gracillariid genera by the elongate saccus in male genitalia, the characteristic from which the genus name derives. -level identification requires examination of genitalia and mine . are tiny (6-7 mm in M. morrisella). Larvae are hypermetamorphic, with distinct sap-feeding and tissue-feeding instar morphologies. Leaf mines are typically blotch-type or tentiform, appearing on the lower leaf surface.

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Habitat

occupy forest understories with native Fabaceae , and in some cases agricultural landscapes. M. morrisella occurs in forest understories with American hogpeanut and slickseed fuzzybean, and has recently colonized soybean fields. Higher in soybean occur at field edges adjacent to wooded areas.

Distribution

Native to North America. M. morrisella documented in eastern North America; recently reported from Quebec, Canada and Minnesota, USA in soybean. M. coursetiae described from Arizona, USA. M. robiniella, native to North America, is in Europe (first documented 1983), now present in Slovenia, Croatia, and Russia (Voronezh region).

Diet

All known are leaf miners on Fabaceae (legume ). Larvae feed internally on leaf tissue, creating blotch or tentiform mines.

Host Associations

  • Fabaceae (legume family) - larval plant All specialize on Fabaceae; specific vary by species

Life Cycle

Hypermetamorphic development with distinct larval instar forms. M. morrisella has five instars: early instars are sap-feeding with specialized mouthparts, later instars are tissue-feeding. occurs inside the leaf mine. Development from to in M. morrisella requires 425 above 8.96°C lower threshold, enabling multiple per growing season.

Behavior

Larvae are endophytic leaf miners, feeding entirely within leaf tissue. oviposit on plant leaves. M. morrisella shows flexible host plant use without genetic differentiation between on different hosts, suggesting dietary plasticity rather than host race formation. M. robiniella produces multiple mine types (lower-side blotch, upper-side blotch, midrib blotch, edge blotch with leaf folding), potentially creating enemy-free space.

Ecological Role

Native herbivores on forest legumes; some have become agricultural pests. M. morrisella has expanded from native to soybean, a major agricultural crop. M. robiniella is in Europe, causing significant damage to black locust (Robinia pseudoacacia). are associated with these leaf miners, including Chrysocharis walleyi (Eulophidae) reared from M. coursetiae mines.

Human Relevance

M. morrisella has emerged as a potential pest of soybean in North America, with heavy (>10 mines per leaflet) documented in Quebec. M. robiniella is an established pest of black locust in Europe. Research is ongoing to assess economic impacts, develop monitoring protocols, and identify in soybean cultivars.

Similar Taxa

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Etymology

The generic name derives from ancient Greek μακρο- (makro-, meaning long) and σάκκος (sakkos, meaning bag), referring to the elongate saccus in the male genitalia.

Species diversity

Six currently recognized: M. coursetiae (Arizona, on Coursetia glandulosa), M. gliricidius, M. morrisella (widespread, on multiple Fabaceae including soybean), M. neomexicanus, M. robiniella ( in Europe, on black locust), and M. uhlerella.

Genomic resources

A 245 Mb assembly exists for M. morrisella with 96.33% BUSCO completeness and N50 of 9 Mb. genomic studies found no genetic structure correlated with geography or plant, with weighted FST of 0.0058.

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Sources and further reading