CHAPTER 1 NOTES ON TAXONOMY & NATURAL HISTORY. (1990). However no single key to the species level is presently available

Transcription

1 CHAPTER 1 NOTES ON TAXONOMY & NATURAL HISTORY Despite the pioneering taxonomic work on Indian ants by FoJ (1900) and Bingham (1903) during the early part of this century, our knowledge of the biology and natural history of Indian ant species ia rather limited. Species, like leaf nest building Oecophylh stnuragdim has caught the attention of the biologists because of it's interesting nesting and territorial behaviour. But, the natural history and biology of other Indian ants have remained grossly neglected. I will attempt to give a brief account of the natural history of the species that I came across in my study area based on existing literature and my personal observation. The taxonomy of Indian ants has not been properly updated in the recent times. I have attempted to identify species upto the generic level mostly following Bingham (1903) and 8. Bolton's taxonomic key of oriental ants as given in Holldobler and Wi (1990). However no single key to the species level is presently available (personal communication, Dr. B. Bolton. Natural History Museum, London and Dr. J. C. Weulersse, Museum National D' Histoire Naturelle, Paris) and I have followed the species level key by Bingham (1903) wherever possible. Species that could be identified upto the species level, have been brietly described along witb their identifying characters in the appendix (I). Table 1.1 gives a summary of the identifying taxonomic ckters of each of the thirty one species and their geographical distribution, recorded from pitfall trap sampling in the primary forest during the period 1990 through Species for which no species level identification was possible, generic characters have been given.

2

3

4

5

6 Foraging and Recruimnt : All the species recorded in this study are ground foragers. Some of them, like Oecophylla smaragdina, Crematogaster wroughtoni. Camponoms spp. forage both on the ground and on vegetation. The others are obligatory ground foragers. Oecophylla smaragdina forages in a group following a scout. Recruitment at a profitable food source found by a scout usually takes between 5 to 10 minutes. Many individuals cany large food items together. 'Iheir ability to retrieve large food items in a group has also been documented in Holldobler and Wilson (1990). Crematogaster wroughtoni. Pheidole sp. 1, Tetramorium tortuosum. Tetramorium sp. 2, Phedologiton sp. and Aphenogaster beccarii also carried larger food items in a group. Aenictus aitkenii, the only member of the subfamily Dorylinae recorded in the study area is a trail forager. This genus has been described as the 'Asian m y ant' resembling the behaviours of famous neotropical army ants like Eciton spp. (Holdobler and Wilson 1990). This species moves in large trails, almost forming a 'moving sheet of ants' (Wroughton 1892, Bingham 1903). They are known for their predatory behaviour and show group retrieval of large prey items. Leptogenys spp., members of the subfamily Ponerinae were group foragers and foraged in trails. They were also found to retrieve large food items in groups. Group.reuieval behaviow of the species of this genus have been described to be conspicuous (Holldobler and Wilson 1990). Monomorium spp. arrived at the bait in large numbers but group retrieval was not observed. Camponorus sp. 1 and Camponorus compressur recruited at the bait. A. beccarii recruited en masse (10-15 individuals) at baits (occasionally), but most of the times it was found to forage alone. Most of the species of the subfamily Ponerinae were solitary foragers except Leptogenys spp. Tandem (pair of foragers, one individual following the

7 scout) foraging was observed in Camponorus compresssus. This has also been reported by Holldobler and Wilson (1990). Among the solitary foragers, the foraging techniques of two species are wonh mentioning in this context A. beccarii uses tools to cany liquid food items lie honey. An individual forager would drop soil panicles in the honey given as bait and then would carry the soil particle soaked with the liquid to it's nest Harpegnathos saltntor, the largest (15-17 mm) ant in the community showed a remarkable feature of catching live prey items by making a jump at the prey (covering at least a distance of 2 to 3 feet), They also showed this behaviour when disturbed. Soans and Soans (1972) reported similar phenomena. Stealthy and camouflaged foraging has been described to be the foraging mode for Strumigenys sp. The 'stealthy' hunting method of this species has been described by Holldobler and Wilson (1990) Food : Most of the species in the study area were generalist scavengers. A few food specialist species were however also present. Species like Borhroponera sp., Odontoponcra sp. are termite specialists. Harpegnathos saltator is also a specialist predator. This species fonges solitarily and has a pair of remarkably long and bent mandible and has large widely separated eyes (vide diagram) which are useful tools for them to catch prey. Their prey items range from cocktoaches and spiders to cicadas and beetles (Maschwia 1981). This species is also known to paralyse the prey by stinging it immediately after catching. Another specialist predator in the study atea is Strumigenys sp. This species also has a long mandible specialized for catching pny. Holldobler and Wilson (1990) has described their mandible as operating like a 'miniature spring tmp'. They are specialized hunters for the collembolans. Species of the ponerine ant genus Phthyrea have been described to show predatory behaviour (Holldobler and Wilson 1990) and on one occasion I have obsewed it to carry a live moth. Most of the ants wen generalists who scavenged on insect carcasses. termites, broods of other insects including social insects, seed coats, floral

8 pans, am floral neccaries or whatever they find palatable. Amciation of Crematogmr sp. with the exwrdloral nectaries of the understorey shrub and tees, especially with blooming Humboldtia brunonis a common understmy species in this forest, is common. Camponotus spp. pnfsr sugar rich food items lii ncctaries and are commonly seen to be returning to their nests with distended gaster. hf~~tn~ri~m spp. were observed to tend coccids for their sugar secretion. As observed in Bingham (1903), Crcmastogaster spp. are known to keep 'ant cante'. Nesting : Most of the myrmicine ants like Pheidole sp.1, Tetramorium rortuosum Tctramorium sp. 2, Phedologiton sp., Monomorium spp. make deeply excavated nests in the ground with multiple chambers and tunnels. Pheidok sp. 1 decorated their nest entrance with seed or floral parts. Another deep wund nesting ant species is the ponerine ant Harpegnathos saltawr. This species also decorates their nest entrance with small pebbles. Aphenogastcr beccarii was the only member of the subfamily Mynnicinae that construct superficial ground nests. This species usually made nests at the base of a tree and below stones or small mks with a horizontal and &ular tunnel shaped nest entrance. They construct the tunnel entrance by making a mat like material with seed and floral parts. The nest has a maximum of two to three chambers. Bigger ants of the subfamily Ponerinae like Odontoponera sp., Bothroponera sp. Odontomnchus sp.. Ectatommn sp., Pseudoponera sp.. Amblyopone belli made superficially excavated nests in soil, mostly below stow or logs. Crematogaster wroughtoni and Crematogaster sp. 2 makes both arboreal nests as well as nests within fallen logs and twigs. The arboreal nests of this species are a carton l ie structure made up of mud and plant tissues. This species also commonly colonized fallen logs and twigs. Interestingly, many of the twig nests did not have a queen but had broods. 'Ihese colonies inside the twigs appear to be satellite nests of a lprger colony. Satellite nesting has been observed commonly in a number of genera

9 (Holldobler and Wilson 1990). 0. smaragdina, was anther species in the study area that makes satellite nest. TbL species, commonly known as weaver ants, arc known 10 make arboreal nests made of joined hves. Leaves are joined by secretions from larval 'silk glands'. Their mode of nest construction has often amacted the amtion of natural historians and has been described a number of times since eighteenth century (Holldobler and W i 1990). Catuhcus rapiobanoc, another Myrmicine ant had colonies in the folded leaves of understorey plants. Camponorus compressus, was found to make nests in the crevices or holes of a uet. On few occasions I had discovered nests within the holes of large roots. Campowha sp. 1 (near im'tanr) were found to make nests under large stone8 or fallen logs. I have also discovered nests of chis species within rotting logs. Colony size : Colony size varies widely among different species of ants. I wil give an approximate account of the colony size of different species based on my personal 0bse~ation and existing literature (Table 1.2). State of colony level study of Indian ants is poor and most of the secondary infonuation provided here are from the existing literature of the equivalent species of the same genus in gographid areas out side India

10 L M ~ P L ulua A01 'UTM A81 'WWM as1 'WWM A61 'UOQM