Some functional aspects of phoresy in mites 573 5 74 E. S. BINNS I have previously suggested that, where little is known of the biology of either phoretic or host, the discovery of a phoretic relationship adds to our understanding of the ecology of each species (Binns, 1972). The wealth of data available for such studies may be gauged from a published compilation of over 800 mite species carried by over 1,300 hosts (Farish, 1965). Nonetheless, only a one-line reference to phoresy in the Acarina is made in a work on The Evolutionary Ecology of Animal Migration of over I ,000 pages (Baker, 1978). T h e problem, however, is to give form to the mass of information. The present study seeks to discover in what sense the assumptions about the role of phoresy inherent in the above definition are consistent with recent theories of migration, particularly those derived from largely independent studies on insects. BEHAVIOUR AND PHORETIC MIGRATION ( I ) Biological necessity for phoresyThe restriction imposed by the biology of mites on the ecology of their dispersal were well summarized for the Tyroglyphoidea (Zakhvatkin, I 959). Thus, the majority are restricted in activity, being clumsy and slow and incapable of covering large distances; their speed varies from 5'2 mm/min in Caloglyphus rodionovi Zakhvatkin to 150 mm/min in Glycyphagus michaeli Oud.; they seldom move in a straight line so that their dispersal is limited. The possibility of active dispersal is further reduced by their narrow ecological limits (mainly in relation to humidity, e.g. Behura, I 956) which permit habitation of only limited micro-climates, which are not constant with distance. Dispersal is vital because of the requirements of the immature and adult stages, and movement is of prime importance as their habitats are scattered or separated by what are for them insurpassable distances. The fluctuating humidity of many habitats necessitates a constant migration of mites between micro-climates in the different regions of the habitat (e.g. in the different layers of plant debris). T h e anomaly of their weak capacity for active dispersal and their urgent biological need for it is solved by employing various means of dispersal: by wind (anemohoria) or by animals (zoohoria), both of which have been described as 'passive' (Zakhvatkin, 1959 and Section I1 (2)). My concern in this review will, therefore, be with the central role of phoresy and its relationship to dispersal or migration. the New York Entomological Socity 65, 51-78. 52, 323-360. University of Kansas Science Bulletin 45, 29-275. by season and host sex. Journal of the Kansas Entomological Society 42. 195-219. Caloglyphus boharti. Journal of Insect Physiology 15, zo45-zo57.

S U M M A R YObservations in mushroom houses showed that the number of larvae of L . auripila in the casing was higher than in the compost throughout the post-casing phase of culture. The intestines of larvae from casing contained both peat and fungal material. Choice of oviposition site was accordingly non-specific. Females from cropping houses appeared to consist of a mixture of monogenic (predominantly unsexual) and digenic (bisexual) strains. Males matured c. 2 days before females at 20 O C ; such protandry appeared to be related to sexual differences in the extent of migration undertaken by the dimorphic sexes.Sciarids were reared from egg to adult equally effectively on (a) detached sporophores or on portions of (b) pileus, (c) stipe or (d) gills, all placed on moist peat, or on detached sporophores placed on a variety of inert substrates. Development was completed where sporophore material was the only food source and also occurred on peat to which only protein, particularly egg albumin, had been added. Hence, assuming no protein metabolism by a third organism, for development in the casing layer to occur, the mushroom need contribute only such proteins. However, their replacement by amino acids was not successful in limited tests.Addition of increasing amounts of the fungal metabolites mannitol and calcium oxalate to compost delayed development, and the accumulation of these materials during fungal growth may be responsible for the antagonism between mycelial and sciarid development which results in subsequent migration of emerging adults.

SUMMARYThe development of sciarids was reduced in old casing and in casing to which a commercial composting additive was added in large amounts. In laboratory tests, adding water, soya bean, cotton seed or oatmeal to finished mushroom composts reduced the mean development time of the larvae of Lycoriella auripila. Soya bean meal significantly increased the number of adult sciarids which matured. While the presence of mushroom mycelium in large quantities inhibited the development of sciarids, smaller amounts increased either the number of larvae maturing or their rate of development in different tests. Larvae were seen to feed on mycelium. The addition of sucrose solution either reduced or prolonged development time in different tests. Nitrogenous additives encouraged the growth of ‘weed moulds’. Both these and the number of sciarids which developed were reduced by adding a solution of calcium nitrate. The results suggested that more selective composts, favouring rapid mycelial colonization, would provide ‘cultural’ control of mushroom sciarids.

ABSTRACT. In the transition from walking to flight in free and tethered aphids, forward progression was more or less abruptly checked and the walking pattern of leg movements gave way to a stationary, treading phase. This was followed by leg extension and wing‐spreading, kicking of the mesothoracic legs, wing‐beating and final lift‐off. Removal of the wings, but not of the middle legs, inhibited this pre‐take‐off behaviour. Jumping appeared to play no part in takeoff, nor did loss of tarsal contact stimulate flight in tethered aphids but resulted only in wing‐raising. However, restoration of tarsal contact often resulted in immediate take‐off, as well as stimulating post‐flight wing‐folding, Wing‐beating, but not wing‐raising, was apparently inhibited during walking.

S U M M A R YThe mushroom sciarid was found to develop on a plant-derived diet of oat or soya meal. Details of simple rearing techniques and insecticidal assays of treated casing are given. I n laboratory tests using ten chemicals, chlorfenvinphos and pirimiphos-ethyl showed persistent activity against larvae when used