Post by Deleted on Oct 29, 2011 7:25:43 GMT 1
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| [bg=fbd9bd] Taxonomy: Formicinae Lasius (Chthonolasius) umbratus Colony type: Monogynous Colony founding: Temporary social parasite Color: Worker yellow-brown, reddish / Queen brown, amber / Male blackish brown Size: Worker 3-4 mm / Queen 7-8mm / Male 5mm Distribution: Throughout North America, Europe, and Eurasia Mating season: August-October Nutrition: Insects, protein jelly, honey/sugar water, honeydew Temperature: 20-27 degrees C Hibernation: Recommended Air humidity: 20%-50% (moderate) Nest building: Rotting wood, loam Planting: Benefits from plants, for aphid/mealybug cultures Class: Easy* First described by: Nylander (1846) Description: Worker: “Usually clear yellow, sometimes reddish, but the whole body of the same colour, size not very variable. Head very slightly emarginate posteriorly; eyes small, as in flavus; ocelli very small and indistinct; frontal furrow indistinct; funiculus of antennae with joints longer than broad. Thorax hairy, pubescent. Scale high, narrowest at apex, slightly emarginate; gaster pubescent and hairy. Tibiae with outstanding hairs.” Donisthorpe (1915) “Genae always with many erect hairs. Whole head, alitrunk, and gaster with many erect hairs and a dense, not ideally parallel pubescence, giving a rough surface appearance. Scale shape varying, but normally clearly notched and with slightly convex sides converging towards dorsal crest. Dorsal surface of scape with decumbent to subdecumbent pubescence and suberect to erect hairs of which the longest may project 35 μm from cuticular surface. Extensor profile of hind tibia normally with 10-30 suberect to erect hairs of which the longest project 45 μm.” Seifert (1988) Queen: “Reddish brown, with the mandibles, antennae, and legs lighter. Head large, as broad as thorax, emarginate posteriorly; funiculus of antennae with joints longer than broad. Thorax pubescent and hairy, only slightly narrower than gaster. Scale emarginate at apex; gaster pubescent and hairy. Tibiae with outstanding hairs. Wings infuscate at the base for half their length, the color considerably darker than in flavus.” Donisthorpe (1915) “Pubescence on head, alitrunk, and gaster very dense, more decumbent than appressed and not ideally parallel, thus producing a slightly rough surface appearance. Nearly all body parts including genae with many erect hairs. Erect hairs on mesonotum long, the longest always longer than 75 μm. Scale shape varying but generally clearly emarginated. Dorsal surface of scape with decumbent or subdecumbent pubescence and very numerous erect or suberect hairs which project at least 26μm (25-50 μm) from cuticular surface. A similar situation exists on the extensor profile of the hind tibia where the number of erect or suberect hairs ranges individually from 16 to 56.” Seifert (1988) Male: “Blackish brown, antennae and legs lighter, funiculus and tarsi yellowish. Head large; mandibles armed with five teeth; frontal furrow distinct; eyes with distinct outstanding hairs.” Donisthorpe (1915) “Masticatory border of mandibles with 4-6 small denticles in addition to the larger apical and subapical dents. Sectional view of scape at midpoint elliptic. Dorsal surface of scape with subdecumbent to suberect pubescence and 2-12 suberect to erect hairs which protrude up to 30 μm from the cuticular surface. Scale normally with convex sides converging towards the dorsal crest that is normally notched. Cross vein m-cu in 69% of wings present.” Seifert (1988) *Colonies are fairly easy to care for, but the adoption of a queen by workers can be notoriously difficult. |
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| [bg=fbd9bd] A member of the Chthonolasius subgenus, Lasius umbratus is a temporary social parasite of other ants in the genus Lasius. Queens are easily recognized by their minimalistic gaster and enlarged head. Mating flights of this species occur during late August and September, but queens may be found wandering above ground during most parts of spring and summer. Flights are massive, with the number of L. umbratus reproductives outnumber those of their host species by as much as 10 to 1. A Lasius umbratus queen must infiltrate a colony of another Lasius species (often between fall and spring,) and take her place as their queen. The large head of L. umbratus is designed for combat with other Lasius. Lasius umbratus is a mostly subterranean species, but it's not unusual for them to forage above ground, too. Wild colonies manage large herds of aphids and mealybugs underground. These ants are known to cultivate Hormiscium pithyophilum var. myrmecophilum (a variation of a black fungus that often appears on the bark of conifers) in their carton walls. This fungus provides a great deal of strengthening to the nest's architecture, but it may also offer some sustenance to larvae; It's been shown that the hyperparasitic Lasius fuliginosus has some difficulty raising brood when umbratus carton is not present. |
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| [bg=fbd9bd] Lasius umbratus must find a host colony of Lasius (L. niger and L. alienus are a favorite, though almost any species of Lasius can be a suitable host.) The primary objective is to make their way into a host colony and copy its odor. Infiltration strategies are various and sometimes inconsistent. ~ Some queens will “fish” for workers at the entrance of a nest, grab hold of one's body, and use the worker as a sort of scent shield to enter the colony. ~ A queen might become very still, and let a worker drag her into the nest. ~ A queen may excavate her own chamber within the soil of the colony, taking time to absorb its scent and possibly turn the resident queen's own workers against her, remotely. ~ Some queens barrel into the colony and take their place upon a pile of brood, which is suggested to be another method of scent absorption. Lasius umbratus often targets the colonies of workers that are orphaned; queenless workers are occasionally receptive to a new queen, and particularly vulnerable to the influence of a parasite. If there is already a queen in the nest, the L. umbratus must remove her, either by convincing the colony's workers that the parasite is a more suitable reproductive, or by killing the queen herself. The umbratus queen might spend days at the side of her target before attacking. No technique is currently perfected for successfully adopting L. umbratus to host workers. Some experiments on parasitic colony founding only yielded a 2% laboratory survival rate for young Lasius umbratus queens. Here are what are considered to be important factors when introducing a queen to host workers: 1. Removing the workers from a colony for a length of time: when workers consider themselves to be orphaned, their attitude towards a new queen improves from what it might have been. 2. Cold introduction: Lower temperatures will decrease the aggression and damage the queen and workers might inflict on each other; It's suggested that you leave them both in artificual hibernation for at least three weeks (during a cold, natural hibernation is when this works best.) 3. Introduce callow workers or naked pupae: It's been shown that Lasius umbratus queens lack the instinct to open up the cocoon of a Lasius pupae, but it's worth experimenting to see if naked pupae might be able to emancipate themselves without assistance, in which case they will almost certainly be adopted by the queen. Callow workers imprint on whatever nest-mates happen to be around for their first few days of adulthood (the queen could possibly object to their presence, though.) Ordinary pupae of the desired species may be offered to a few workers that were introduced as callows, who can open these cocoons. It's worth noting that if a Lasius umbratus queen has been successfully adopted by mature workers, and within a reasonable time, more workers can be added from the host colony without huge risk to your queen, who has copied the colony's scent (still, it's risky!) It may take a couple months for a successfully adopted queen to begin laying, however as a social parasite, Lasius umbratus will create an output of eggs proportionate to the number of host workers in the colony. A queen may produce more than 100 eggs in her first sitting! The Lasius umbratus workers will very quickly outnumber the host workers. |
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| [bg=fbd9bd] Found in soil and rotting wood. Lasius umbratus often constructs intricate galleries of carton, underneath the roots of the plants where it nests. The carton cells are quite tough, and help to support the nest under the impressive amount of excavation that occurs. The walls of these nests are composed mostly of quartzite sand, sugar, and wood pulp. The Hormiscium fungus that grows on these walls adds strength to the nest, and possibly a small amount of nutrition. These ants may be kept in any kind of setup, though they do best in nests of stone or dirt. If you wish to see carton, then you should make sure that its materials are abundant within the nest. |
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| [bg=fbd9bd] Wild populations depend on herds of aphids and mealybugs. Captive colonies may enjoy sugary water, insects, and/or protein jelly. |
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| [bg=fbd9bd] Lasius umbratus enthusiastically cultivate aphids, mealybugs, and Hormiscium fungus. They are a fine example of agriculture in Northern ants. Before hibernation, they can often be seen above ground, searching for the eggs of their livestock. Workers are usually calm, but will aggressively defend their brood when threatened. As Formicines, they make use of formic acid in combat. |
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| [bg=fbd9bd] Lasius umbratus should be hibernated. |
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[bg=fbd9bd] “The intricate galleries in this underground nest of Lasius umbratus ants are made possible by a fungus that grows within a matrix of wood pulp sculpted by the ants.” Alex Wild Image copyright by Alex Wild  A Lasius umbratus queen. Image from bugsandweeds.co.uk |
