The standing crop of woody litter (317 g m) and its rate of production (30.8 g m a) and disappearance (27.8 g m a) were measured in Tsavo National Park, Kenya, at a site with a mean rainfall of 352 mm a. Dead wood took about 11 years to disappear completely. Almost all of this wood is removed by termites, 90% by the fungus-cultivating subfamily Macrotermitinae.

The foraging activities of termites were measured at nine sites distributed along a rainfall gradient in Tsavo National Park, Kenya. Dead wood disappearance (D, g ma) was mainly attributable to termites and was related to rainfall (R, mm a) by the equation [Formula: see text] Foraging activity was highest during rainy seasons and declined to low levels during the long dry season. The number of species increased with increasing rainfall while the importance of fungus growing Macrotermitinae declined.

No abstract

Pine forests of the Mediterranean area are subject to very serious depredations by the caterpillar of the Pine Processionary Moth. Although there are suitable habitats in other parts of the world, the moth has so far remained within this region because of its poor power of dispersal. Traditional methods of containing it are unsatisfactory and better results are to be expected from measures designed to stabilise the population at an acceptable level rather than to eradicate it entirely.

Differences in the timing of pupation of pine irocessionary caterpillars on a native pine and on an exotic species caused marked differences in t e exposure of the caterpillars to parasitism by the tachinid Ph'hryxe caudatu. This result may help to explain the occurrence of outbreaks of the caterpillar in plantations, especially of exotic line?.The possibility t at, in addition to direct defences, plants may have evolved indirect defences based on manipulation of the plant herbivore relationship, to allow suppression of the herbivore population by its parasites or predators, is discussed. , ,However BILIoTrr (1956) reported that this expectation is not fulfilled, especially in areas prone to severe outbreaks of the caterpillars. In autumn the young caterpillars are all susceptible throughout the time when the flies from the summer generation lay their eggs, but in spring a large proportion of caterpillars pupate, and become unavailable, before the winter generation of P. caudatu emerge as adults.Pinus rudiuta has been introduced to the Mediterranean area from California. Apart from fortuitous effects (JANZEN 1980), we may expect this species to lack the specific defences against Th. pityocumpa which we would expect to have evolved in indigenous /~l~t r , t r i , , r ) p o c . , i -S ! . m p ,~\ i i i n i . TVcii\t.i~lt ,I. Rhs~.. nT.ir Fl.iiiiio\ TI' 5.-7.jul\ 1989. U.S. Copyright Clearance Cenrer Code Statement: 093 1 -2048/90/0903-0302 $ 02.50/0 Influence of host tree species on timing of pupation of Th. pityocumpa 303 species of pine ( RHOADES and CATES 1976). In a mixed plantation of P. radiata and the native Pinus pinaster, the American species was preferred for oviposition, and on it the caterpillars grew larger and pupated earlier than on the indigenous trees (own unpublished data). The earlier pupation meant that the proportion of caterpillars available for parasitism by Phryxe caudata was much lower on P. radiata than on P. pinaster. This is consistent with the hypothesis that P. radiata lacks specific defences and poses the question of whether the defence strategy of P. pinaster has been selected to effect synchrony of the caterpillars with its parasitoid. Fig. 4. The proportions of eclosed Phryxe cuudutu puparia in each nest dissolved (frequency of nestsfor any proportion and day), the aggregate proportion for all nests taken on one day (-) and for comparison, the cumulative percentage of P. cuudutu taken from the net traps (2)

No abstract