A new species of Megalommum Szépligeti (Hymenoptera, Braconidae, Braconinae); a parasitoid of the pistachio longhorn beetle (Calchaenesthes pistacivora Holzschuh; Coleoptera, Cerambycidae) in Iran

Abstract A new species of the genus Megalommum Szépligeti (Hymenoptera: Braconidae: Braconinae), reared from the pistachio longhorn beetle (Calchaenesthes pistacivora Holzschuh; Coleoptera: Cerambycidae), is described and illustrated. The genera Curreia Ashmead, 1900 and Endovipio Turner, 1922 are new synonyms of Megalommum Szépligeti, 1900. Notes on the biology of Megalommum pistacivorae sp. n. and a key to the West Palaearctic and Oriental species are added. The following new combinations are given: Megalommum xanthoceps (Fahringer, 1928), comb. n., Megalommum jacobsoni (Tobias, 1968), comb. n., Megalommum ayyari (Watanabe, 1950), comb. n., Megalommum philippinense (Baker, 1917), comb. n., Megalommum dodecanesi(Ferrière, 1922), comb. n., Megalommum ceresense (Turner, 1922), comb. n., Megalommum inareatum (Granger, 1949), comb. n., Megalommum antefurcale (Szépligeti, 1915) comb. n. and Megalommum tibiale (Ashmead, 1906), comb. n.


Introduction
In 1999 a conspicuous longhorn beetle (Coleoptera: Cerambycidae), was collected from pistachio trees, Pistacia vera Linnaeus and P. atlantica subsp. mutica (Fischer & C.A. Meyer) at Sirjan (South Iran) for the first time. The beetle (Figs 7,8,10) proved to be undescribed and was named as Calchaenesthes pistacivora by Dr C. Holzschuh (Holzschuh 2003). According to Hashemi-Rad (2005) the pistachio longhorn beetle caused very severe damage to weakened pistachio trees. During April, 2007 the second author managed to rear a parasitoid from the longhorn beetle, which may play a role in the biological control of the pest. It proved to be a new species of the genus Megalommum Szépligeti near jacobsoni (Hymenoptera: Braconidae: Braconinae). The new species, M. pistacivorae, is described below. It is the first record of a cerambycid host for the genus, and is the first record of the genus Megalommum from Iran.

Material and methods
The material was partially reared from the larvae of the pistachio longhorn beetle boring in pistachio trees and partially collected at light in the wild pistachio growing areas of Sirjan (South Iran). The material is deposited in the Netherlands Centre for Biodiversity Naturalis at Leiden (RMNH).
For the recognition of the subfamily Braconinae, see van Achterberg (1990Achterberg ( , 1993Achterberg ( , 1997, for a key to the genera of Braconinae, see Quicke (1987), and for the terminology used in this paper, see van Achterberg (1988).
No taxonomic history is presented in this paper; for information, we refer to the Taxapad interactive catalogue (Yu et al. 2007 and later updates).

Key to West Palaearctic and Oriental species of the genus Megalommum Szépligeti
Description. Holotype, ♀, length of body 7.6 mm, of fore wing 7.3 mm. Head. Antenna about as long as fore wing, with 61 segments; apical antennal segment with distinct spine and slender, scapus robust and distinctly protruding apically, its inner aspect with minute double margin apically; third, fourth and penultimate segments 1.2, 0.9 and 1.6 times their maximum width, respectively; length of maxillary palp 0.9 times height of head; eye distinctly emarginate (Fig. 3); face narrow and irregularly rugulose; clypeus flat, partly smooth and with some microsculpture, dorsally with angled carina and ventral margin thin and lamelliform, with 5 long setae ventrally; hypoclypeal depression 0.7 times as wide as minimum width of face (Fig. 3); frons moderately concave behind antennal sockets, smooth, without median carina (Fig. 16); vertex slightly convex, smooth, sparsely setose and stemmaticum protruding and surrounded by a groove; OOL:diameter of posterior ocellus:POL = 5:10:4; in dorsal view length of eye 5.2 times temple; temples directly narrowed behind eyes and smooth (Fig 16); malar suture absent, eye almost touching base of mandible; mandible strongly twisted and unidentate.
Mesosoma. Length of mesosoma 1.6 times its height; side of pronotum and propleuron smooth, except for some indistinct fine crenulae anteriorly and some punctulation posteriorly; pronotum vertical anteriorly and with a shallow groove and no antescutal depression; mesopleuron smooth, setose, except for a medial glabrous area; mesosternal sulcus smooth and narrow; metapleuron punctulate, convex; mesoscutum nearly completely sparsely punctulate and setose; notauli only present anteriorly and shallowly impressed; scutellar sulcus present and with distinct fine crenulae; scutellum weakly convex and sparsely punctulate; side of scutellum smooth; metanotum medioanteriorly with carina, posteriorly evenly convex and smooth; propodeum smooth, setose and evenly convex.
Legs. Tarsal claws simple and with bristly setae ventrally; hind femur slender (Fig. 20) compared to M. jacobsoni; length of femur, tibia and basitarsus of hind leg 3.9, 10.0 and 4.7 times their maximum width, respectively; hind tibia with dense adpressed setae; hind tibial spurs 0.5 and 0.6 times as long as hind basitarsus; inner side of hind tibia and tarsus with dense long whitish setae.
Metasoma. Length of first tergite 1.1 times its apical width, parallel-sided, dorso-lateral carinae strong behind spiracles and medial area longitudinally rugose; second tergite smooth except for crenulae near distinct triangular medio-basal area, area surrounded by crenulate groove and tergite antero-laterally with small triangular smooth areas (Fig. 18); second suture distinct and weakly sinuate and finely crenulate; medial length of second tergite 1.2 times median length of third tergite; third and following tergites smooth; ovipositor depressed, without notch or nodus dorsally and without ventral teeth, apically narrowed (Fig. 76); ovipositor straight, its sheath 0.25 times as long as fore wing.
Colour. Yellowish-brown; antenna, hind femur dorsally, hind tibia and tarsus and ovipositor sheath, black; fore and middle femora, tibiae and tarsi, and remainder of hind leg more or less dark brown; most veins of basal half of wing, sclerome of first subdiscal cell and apical 0.6 of pterostigma largely dark brown (Fig. 2), vein 1-R1 of fore wing yellowish and remainder of veins brown; wing membrane moderately infuscate, below parastigma and patch in first subdiscal cell dark brown.
Etymology. Named after the specific name of its host.

Biology
The development of the cerambycid host Calchaenesthes pistacivora Holzschuh lasts two years; the first winter it survives as a larva and during the second autumn it usually develops into an adult (Hashemi-Rad 2005). The adult beetle stays inside the feeding canal (Fig. 10) for about five months, from mid October to late March. In early April, the adult beetles appear on the pistachio trees and usually feed on the fresh pistachio leaves (Fig. 7); the resulting damage is considered to be minimal. The beetles lay their eggs on twigs, branches or stems of weakened pistachio trees, preferably on the pruned sites where the tiny larvae promptly penetrate into the twigs or branches. Changes in the environmental conditions of pistachio growing areas in the collection site are thought to be drought, an increase of salinity in irrigation water, which in turn is caused by a decrease of water resources and mismanagement by pistachio producers. These appear to be the major reasons for the establishment and development of this pest on cultivated pistachio trees (Hashemi-Rad 2005). It is predicted that the contaminated areas will expand as more pistachio trees lose vigor. Our survey in wild pistachio growing areas of Sirjan clearly showed that C. pistacivora had already been living in the wild pistachio trees for a long time, because the beetle canals are clearly visible on both dead and living trunks of very old trees of Pistacia khinjuk Stocks (Figs 4,5) and P. atlantica mutica. It is assumed that the beetle has been a minor phytophagous pest on wild pistachio trees for hundreds of years, however, populations increased due to weakening of these trees. The wild pistachio species have been suffering from the effects of erosion caused by human activities, particularly overgrazing and harvesting for use as firewood or charcoal as well as from severe drought periods for several years. In addition, the cultivated pistachio regions at Sirjan are not far from areas with wild pistachio trees. Therefore, emigration of C. pistacivora to pistachio orchards is likely. At present the pistachio growers experience many serious problems caused by pests and diseases (Mehrnejad 2001) and the longhorn beetle is one of those that can cause considerable tree damage and reduction of yields. The cocoons of the parasitoid were collected inside the tunnels of the beetle (Fig. 6). The cocoons are 12-15 mm long, brownish and consist of thin paper-like silk. The beetle usually pupates inside the tunnel about 2-3 cm from the emergence hole, where the cocoons of M. pistacivorae are also found. Field studies showed that the parasitoid enters the tunnel of the beetle through the hole made by the last instar beetle larva before pupation. The parasitoid attacks the last instar beetle larva in September and October and the parasitoid larva is solitary. Members of Braconinae are all thought to be ectoparasitoids. Surprisingly, the second author did not see any parasitoid larva or egg when he collected a fully developed beetle larva from the feeding tunnel. The beetle larva (still in the tunnel) was transferred to the laboratory where it was kept under controlled conditions. After a week a naked pupa of the wasp (that did not construct the usual cocoon) was present and the pupa developed into an adult M. pistacivorae. Further investigations are necessary to rule out the possibility that a minute wasp larva was present on the non-exposed side of the beetle larva.
M. pistacivorae overwinters in the prepupal stage and it has an obligatory diapause to pass the winter. The parasitoid cocoons containing the prepupa were kept under controlled conditions (27.5°C, 16L:8D photoperiod and 55±5 RH), but they did not pupate until early March. In the field, pupation takes place from mid to late March and the adults of M. pistacivorae appear in the orchards from early April onwards. The rate of parasitism was estimated to be about 23% (n = 110) in experimental orchards. Alternative hosts for this parasitoid remain undetermined, also it is not clear if the adult wasps attack another host after emergence in early April or they pass the hot summer period and attack the larvae of C. pistacivora the following September.
In the same tunnels several other insects were found; the most common was a bee belonging to the genus Hylaeus. It uses the tunnels as shelter for its brood cells. Several small cells of bees are usually found at the same site where M. pistacivorae makes its cocoons (Fig. 15). From late September till late October the female bee makes 3-5 small cells (4 mm length and 3 mm diameter each) in each tunnel, and fills them with a yellowish jelly mixed with pollen. In each cell an egg or a young larva was found (Fig. 12). The female bees cover the emergence hole (tunnel cup) with a very thin and delicate grayish waxy layer (Fig. 14). The cover protects the offspring of the bee as well as that of the wasp, M. pistacivorae, against predation or parasitism during the overwintering period. The bee larvae overwinter in these cells at the prepupal stage and pupate from late March on. The tunnels are also used as a nest site (Fig. 13) by a Crabronid wasp.