Lytta nuttalli

Distinguished from similar Lytta species by its specific purple-green iridescent coloration and geographic range. May occur in mixed colonies with L. viridana and L. cyanipennis; L. viridana has a shorter flight period (late May to late June) compared to L. nuttalli (early June to early August). L. cyanipennis flies mid-June to early July. Accurate identification may require examination of male genitalia; the aedeagus is of the vaginate type typical of the genus, with seven pairs of muscles and one unpaired muscle associated with the aedeagus and ninth sternum.

Native prairie habitats, particularly in areas with abundant leguminous vegetation. Adults commonly found in aggregations near bodies of water. Oviposition requires moist, firm soil; eggs desiccate rapidly without moisture. Larval development occurs in nests of solitary ground-nesting bees.

Canada: Alberta, Saskatchewan, Manitoba. United States: Idaho south to Arizona, east to Minnesota and New Mexico. Disjunct population in eastern California restricted to higher altitudes. Core range centered in the Great Plains and prairie provinces.

Adult flight period extends from early June to early August. Peak activity occurs during summer months when host legumes are in growth. Embryonic development of eggs takes approximately 2-3 weeks at temperatures of 15-30°C, corresponding to normal summer conditions.

Adults feed primarily on wild legumes, showing preference for cultivated legumes when available. Documented feeding on soybeans, sweetclover, alfalfa, and other legume crops. Will consume non-leguminous plants including Iris, Delphinium, and Brassica species, plus sugar beets, oats, barley, and wheat when legumes are scarce. Larvae are parasitoids, feeding on bee larvae and stored provisions in nests of solitary bees (family Apidae).

• Megachile sp. - parasitoidLarvae develop in nests of leafcutter bees; first recorded field observations of Lytta oviposition documented in area with remains of Megachile nesting cells
• Apidae (solitary bees) - parasitoidLarvae feed on bee larvae and food stores in ground-nesting solitary bee nests; natural populations limited by availability of native ground-nesting bees

Complex hypermetamorphic development with distinct larval phases. First instar larvae (triungulins) are active and seek out host bee nests. Subsequent instars are parasitic, feeding within bee nests. Pupation occurs in host nest or soil. Embryonic development of eggs requires 2-3 weeks at 15-30°C. Eggs are deposited in batches averaging 320 eggs; females produce multiple egg batches. Moisture critical for egg survival—eggs desiccate rapidly without soil contact.

Adults are gregarious, feeding in groups on host plants. Form mixed colonies with congeners L. viridana and L. cyanipennis. Cross-mating between L. nuttalli and L. viridana occurs in nature, producing hybrids. Both sexes mate multiple times in captivity. Adults prefer moist, firm soil for oviposition. First field observations of oviposition behavior documented for this genus.

Adults function as herbivores, consuming legume vegetation and occasionally facilitating nutrient cycling through plant tissue consumption. Larvae act as parasitoids of solitary bees, potentially regulating bee populations. Natural populations are self-limited by host bee availability, preventing overexploitation of either host or plant resources.

Occasional agricultural pest when adults aggregate on legume crops including soybeans, alfalfa, and sweetclover. Poisoning risk to livestock when beetles are consumed in hay or forage due to cantharidin content—a chemical defense synthesized by adult beetles. Not considered a serious pest because natural population limitation via host bee dependence prevents large-scale outbreaks. Historical interest in taxonomy as one of the early North American beetle species described by Thomas Say.

• Lytta viridanaOccurs in mixed colonies with L. nuttalli; distinguished by shorter flight period (late May to late June vs. early June to early August for L. nuttalli) and different coloration
• Lytta cyanipennisSympatric in Canadian prairies; flight period mid-June to early July, intermediate between L. nuttalli and L. viridana
• Lytta reticulataRelated congeneric blister beetle with different geographic distribution and color pattern

• blister beetle
• Meloidae
• parasitoid
• hypermetamorphosis
• legume feeder
• bee parasite
• iridescent
• prairie insect
• agricultural pest
• cantharidin

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Meloidae Holdings | Entomology Research Museum
• UC Davis Bio Boot Camps: Where Science Matters | Bug Squad
• Grasshoppers of Colorado
• Scathophagidae | Beetles In The Bush
• Friday Flower – Sedum pulchellum | Beetles In The Bush
• blister beetles | Beetles In The Bush | Page 3
• The anatomy, histology, and physiology of the reproductive systems of Lytta nuttalli Say (Coleoptera: Meloidae). II. The abdomen and external genitalia
• OBSERVATIONS ON THE ONTOGENY AND HABITS OFLYTTA NUTTALLI,L.VIRIDANA, ANDL.CYANIPENNIS(COLEOPTERA: MELOIDAE): THE ADULTS AND EGGS