Ants. M. V. Brian

Ants - M. V. Brian


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sensitive response to social conditions.

      Males are either the same size or smaller than the females and they are usually darker. Their antennae are straighter and clumsier and cannot be folded back against the head. They have well-developed compound eyes and ocelli. Their thorax, like that of the sexual females, carries two pairs of wings linked by hooks and it is composed of plates separated by sutures but their petiole is not quite so well-developed. There is no sting at the end of the abdomen; in its place are appendages for locking on to the female during copulation. They do not possess large body reserves like the sexual females.

       TYPES OF BRITISH ANT

      IDENTIFICATION

      Three keys are given here: the first to sub-families, the second to genera and the third to species. These are based on characteristics shown by workers and, in those species which lack them, queens; males help a great deal but for simplicity have been left out. To identify ants as far as the species is difficult; indeed, experts are often not in agreement about some very similar forms. Nevertheless the four main genera, Myrmica, Leptothorax, Lasius and Formica, have been here divided into their most common and easily identified species. The key is not based solely on structural features but includes in a few places reference to habitat, nest site and shape and other aspects of natural history. A low-powered stereoscopic microscope is best for assessing many characteristics but a hand lens may sometimes be adequate. Many distinctions are comparative, e.g., hairy or not hairy, and it is obvious that in these cases experience and reference to a reliable, modern collection is essential.

       Key to sub-families

1Waist of 2 small segments (fig. 1)Myrmicinae
Waist of 1 segment2
2Gaster constricted between segments 1 and 2, with a well-developed stingPonerinae
No constriction, no sting3
3Five segments of the gaster visible from above, a circular orifice for ejecting venom fringed by guide hairs (fig. 7)Formicinae
Four segments of gaster visible from above, no circular orifice but a slit through which viscous defensive fluid is passed, no hairsDolichoderinae

       Key to genera

APonerinae
Only one certain British species, Ponera coarcta, exists; it is a slow, timid ant with small colonies
BMyrmicinae
1Queens black, with shallow, longitudinal trough on gaster, no workers; in Tetramorium caespitum nestsAnergates
Otherwise2
2No spines on the rear of the mesosoma, antennae of 10 segments, the last 2 forming a clubSolenopsis
Mesosoma toothed or spined at the rear3
3Second waist segment with a forwards-directed spine underneath4
No such spine5
4Antennae 11-segmented, tibial spurs on legs 2 and 3, in Formica rufa nestsFormicoxenus
Antennae 12-segmented, no tibial spurs on legs 2 and 3, no workers; in Myrmica nestsSifolinia
5Jaw sickle-shaped; in nests of Tetramorium caespitumStrongylognathus
Jaw with teeth6
6First waist segment elongate, eyes minuteStenamma
First waist segment not elongate, eyes normal7
7First waist segment oblong from side with 2 tubercles aboveMyrmecina
Segment not so8
8Front of first thoracic segment squared dorsally, small black antsTetramorium
Front of first thoracic segment rounded dorsally, reddish-brown ants9
9Last 3 antennal segments shorter than the rest of the funiculusMyrmica
Last 3 antennal segments about as long as the rest of the funiculusLeptothorax
CFormicinae
IOcelli large and distinct, legs long, segments 2–5 of the funiculus longer than all the rest togetherFormica
2Ocelli very small and indistinct, legs short, segments 2–5 of the funiculus shorter than all the rest togetherLasius
DDolichoderinae
Only one British species, Tapinoma erraticum, exists; it has small, black, agile workers which run about with their gaster raised

       Key to species

AMyrmica
OScape of antenna near point of attachment to head bent gradually and smoothly without ridges; head relatively shiny, especially the frontal area (fig. 6c)1
Scape bent sharply through a right angle, with or without ridges, head dull, matt (fig. 6d)2
1Epinotal spines long in relation to body size; either workers large, queens larger than workers, fewer than 10 in a colony (macrogyna)
or
queens same size as workers, more than 10 in a colony (microgyna)ruginodis
Epinotal spines short in relation to body size; workers small, queens much larger, up to 100 in a colonyrubra
2Antennal scape without ridge or teeth; frontal area with marked striations; a dark ant in moorlandsulcinodis
Antennal scape with ridges or teeth at the bend3
3Scape with very characteristic transverse ridge or plate at bend, almost tooth-like from some aspects; a small, dark specieslobicornis
Scape with lateral ridge at bend, reddish-brownscabrinodis
(fig. 6d) andsabuleti
image

      FIG. 6. Worker of Myrmica rubra: a. head, b. foreleg, c. scape of antenna, d. Myrmica scabrinodis: scape of antenna. c. and d. are viewed from behind. Hairs are abundant on the head which is strongly corrugated.

scabrinodis is a smaller ant and has a less pronounced lateral ridge than sabuleti; it also has more queens in each colony
BLeptothorax
OAntennae with 11 segments; a relatively large speciesacervorum
Antennae with 12 segments; a relatively small species1
IClub of funiculus no darker than the rest of the antenna; a distinct dorsal groove or depression across the middle of the mesosoma; nests in tree stumps and woodnylanderi
Club of funiculus darker than the rest of the antenna; no transverse groove on the mesosoma; rare speciestuberum
andinterruptus
image

      FIG. 7. Worker of Lasius niger: a. head; b. scale on petiole from behind; c. side view of tail segments to show ring of hairs around the circular orifice. The whole body is covered with a light pubescence and there are short, erect hairs on the scape of the antenna but none of these have been shown.

CLasius
OColour jet black, shiny, head heart-shapedfuliginosus
Colour otherwise, head normal1
1Colour brown to dull black2
Colour yellow4
2Scape of antenna
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