Pergidae of the World
An online catalogue of the sawfly family Pergidae (Symphyta).
Biology and food plant data are still lacking for most pergid species. Where known, habits are fascinating and varied. Food plants are extremely diverse and those for the Australasian fauna are much better known than for the Neotropics. Though many of the Australian species feed on various species of Eucalyptus (sensu lato), others have such divergent food plants as dead or dying leaves (Diphamorphos, Polyclonus atratus), (semi-)aquatic ferns (Warra froggatti), and fungi (Decameria rufiventris). Most are external leaf feeders, though some are shoot borers (Enjijus) or leaf miners (Corynophilus and Phylacteophaga). Larvae of some Perreyia species travel in groups on the ground and eat dead or dying vegetation. Some Euryinae are saprophagous, live on or close to the ground, and are crepuscular or nocturnal.
Pergidae exhibit several modes of oviposition and eggs are ofen placed in rows under the epidermis of the leaf or in the midrib. The diversity of oviposition types is similar in extent to the diversity of oviposition behaviours across the northern symphytan families, although in these groups eggs are usually deposited singly and embedded in the tissues of their host plants. A few species have vestigial ovipositors and eggs are placed on the surface of the host plant in sheltered places (Cladomacra). Pterygophorinae (Lophyrotoma and Pterygophorus) place their egg in the leaf margin (see figure below). The young larvae often feed in aggregations and only later instars are solitary. In Perginae the eggpod consists of a row of eggs and is placed along the midrib of the plant leaf. The female stands on the leaf surface and deposits the egg through the midrib and into the leaf. The young larvae assemble into a tight circular position where either the heads or ends of the abdomen are juxtaposed at the periphery, with the remaining larvae at the centre, a behaviour referred to as cycloalexy. Females of Styracotechys dicelysma place a single egg into the midrib of the leaf. The larvae feed solitarily at the leaf margin. Females of the three known Australian species of Philomastix scatter their eggs on the underside of the leaf by cutting a slit through the upper surface of the leaf pushing the egg through the hole, and attaching the stalk of the egg to the leaf. Females of all the three known species then guard their eggs and feeding larvae.
Major oviposition characteristics of Australian pergid sawflies (from left to right): Pterygophorinae (eggpod along leaf margin), b) Perginae (eggpod along midrib of leaf), c) Styracotechyinae
(single egg in midrib), d) Philomastiginae (scattered eggs on leaf underside with guarding female above). (From Schmidt et al. 2006)
Maternal care occurs in several species of Australian Pergidae and South American Pergidae and Argidae. In Australia, females of Pseudoperga species guard their eggs and young larvae producing a buzzing sound with jaws open when disturbed, until they die after several weeks. A similar behaviour show species of Philomastix, and apterous females of Cladomacra which were collected under bark on a log standing over a batch of eggs. In South America, maternal care has been observed in Syzygonia cyanocephala which feeds on foliage of Tibouchina spp.
Mating behaviour has been studied in detail in Lophyrotoma analis and it is similar to most strophandrious sawflies studied in this respect. After long distance attraction by the female the mating is initiated by the male and the subsequent behavioural sequence can be divided into several steps. For some pergids, in particular species of the Perginae, there are only very few observations of mating, which has led authers to suggest that other modes of reproduction predominate within the subfamily. However, there is no clear evidence that amphitokous parthenogenesis occurs within the Perginae (or in any other pergid subfamily) or is even the prevalent mode of reproduction in this subfamily.
Mating of Lophyrotoma analis, left: male aligns to female, middle: male attaches apex of abdomen to the female abdomen, right: mating position. (From Schmidt et al. 2006)
Long distance attraction
At least one species of pergid sawflies (Lophyrotoma analis) uses pheromones as long distance sex attractants. The virgin females (but not mated ones) attract males in the field. The high numbers of sensilla on the greatly enlarged surface area of the male antennae (picture right, from Schmidt et al. 2006) indicate that only nano quantities are used for the long distance communication of L. analis.
Some pergids can be economically important because of their defoliation. Species of Tequus feed on potato in Peru and Bolivia, Cerospastus volupis defoliates Nothofagus in Chile and Argentina, a large number of species defoliate (Perginae) or mine in the leaves (Phylacteophaginae) of various species of Eucalyptus in Australia. In particular the leafminers of the genus Phylacteophaga have been of concern in New Zealand and New Caledonia since being introduced into those countries. Other species of Haplostegus, Enjijus, and Sutwanus feed on the foliage or are shoot borers of guava, Psidium spp., in Central and South America, and Acordulecera species defoliate oaks and hickories in the eastern North American deciduous forests. Some species are of concern to agriculture in Australia (Queensland), Brazil, and Uruguay where larvae are known to be poisonous to livestock if ingested (e.g. Lophyrotoma interrupta, Perreyia lepida). Two species are of potential value as biological control agents of invasive weeds in the United States. Lophyrotoma zonalis from Australia has been considered for release against Melaleuca quinquenervia in Florida, and Heteroperreyia hubrichi against the Brazilian Peppertree, Schinus terebinthifolius.