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An account is given of an investigation made of the life-histories of Oscinella frit and its parasites in Ontario, Canada, with a view to the possible introduction of suitable parasites into England. The various Chloropid species associated with O. frit in North America are discussed.The life-history of the frit-fly in Ontario is similar to that in England except wheat, not oats, is attacked, and that there appears to be no regular grain-infesting generation, but the insect is never a major pest in Canada.The life-histories of the following six species of parasites are described : Hexacola sp. n., Polyscelis sp. n., Loxotropa sp., Cyrtogaster sp., Callitula bicolor and Spalangia drosophilae. Other hosts from which these parasites have been reared include Chloropids associated with O. frit in wheat, namely O. carbonaria, O. soror, O. minor and Meromyza americana.A brief account is given of the control exerted by these parasites on the population of frit-fly in Ontario and a comparison is made between the Canadian and English parasite complexes. From this it is concluded that S. drosophilae might exert some control of frit-fly if introduced into England.

In a previous paper (Simmonds 1946*) the biology of Phytodietus pulcherrimus (Cress.), a parasite of Loxostege sticticalis, L., the sugar-beet web-worm, has been described. This paper will be devoted to the habits and life-history of another important parasite of Loxostege in North America, Bracon vulgaris (Cress.). This species appears to be confined to the American continent, all of the records being from Canada and the U.S.A. It has been reared only from Loxostege sticticalis, L., and L. commixtalis, Wlk. From the former species it has been recorded by Paddock (1912), Swenk (1918), Jones, Hoerner and Corkins (1921), Pepper and Hastings (1941), and Simmonds (1946); from the latter species by Hoerner (1933). During the present work it has been reared from L. sticticalis, material from both Montana and Alberta.

Experiments were designed to determine the criteria by which an ovipositing female of Spalangia drosophilae Ashm. is attracted to an environment where suitable hosts may be found, and by which these hosts are selected.The results obtained indicate that ovipositing female Spalangia are attracted to and maintained in areas where suitable host puparia may occur by their reaction to sensory impressions. Thus females tend to be attracted to dampness and to soil level where, in grasses, host material is likely to be found. In such an area searching for hosts appears to be at random, but once an object that is a possible host is located there follows a careful examination and, if the object is “ considered ” a suitable host, oviposition follows. It appears that there are several definite criteria by which an object is accepted as a host suitable for oviposition. In general the hosts selected by the parasite are those which are suitable for the development of her progeny.

When an insect parasite successfully attacks a host in the natural environment, the criterion of success being the development of the parasite progeny to maturity, the species attacked is described as a “natural host.” Parasites are used in biological control work with respect to their natural hosts. However, when the mass breeding of parasites for field distribution has to be carried out, the provision of natural hosts in sufficient quantity is in many cases difficult or impossible, unless they can be easily obtained in large numbers from the field. But some of these hosts have only a single generation a year. Others live in the larval stage in parts of growing plants which cannot be satisfactorily handled so as to produce mass infestations; on the other hand, attempts to rear such insects on detached fragments of plant tissue often result in heavy mortality. Other hosts which are very satisfactory for parasite propagation in some respects, become very susceptible to epidemics of disease when kept in large numbers in confinement. Even without these difficulties, the propagation in the laboratory of large numbers of natural hosts is often tedious and expensive.

A description is given of a technique for breeding the parasite Spalangia drosophilae Ashm. (Spalangiidae). Various biological “constants” such as fecundity and longevity were studied at 70°, 75° and 83°F., and the variation in the figures for these is given. The oviposition rate, efficacy of single matings, sex ratio, percentage in diapause, developmental period of both male and female at the different temperatures are also give.

In an intensive study, begun in 1955, on the biological control of Pseudaulacaspis pentagona (Targ.) and Pulvinaria psidii Mask. on oleander (Nerium oleander) in Bermuda, several species of COCCINELLIDAE were successfully established, but none developed a population sufficient to control either scale. The failure of these apparently suitable species of Coccinellids was therefore investigated. It seemed possible that insectivorous lizards, which are very abundant everywhere, might be responsible.Dissection of a number of lizards, Anolis grahami, and A. leachi, in the autumn and winter indicated that at both these times their effect on the natural enemies of scale insects in general and of Pseudaulacaspis pentagona and Pulvinaria psidii in particular, was considerable. Both Coccinellids and Hymenopterous parasites were eaten in large numbers. A surprising number of very small insects including ants, was eaten, and although a number of the insects eaten are harmful, on balance it would appear that, particularly with regard to the biological control of scale insects, the elimination from Bermuda of these lizards, which are introduced species, would be beneficial.Experiments are being carried out to test this, and the introduction of predacious birds, particularly that of the Trinidad kiskadee, Pitangus sulphuratus, is planned.