In 1910 in a paper on the parasites of the Gypsy and Brown-tail moths, W. F. Fiske calculated the mortality necessary to stabilize the gypsy moth population and stressed the importance of a sequence of parasites and predators attacking successive stages of the insect host, in the establishment and maintenance of satisfactory control. In 1912, in the bulletin entitled “The Importation into the United States of the Parasites of the Gypsy Moth and Brown-tail Moth”, L. O. Howard and W. F. Fiske studied the problem of a sequence of parasites much more fully. They then made the very important point that aggregate percentage of kill necessary for the control of an insect pest could not be secured by simply adding together the figures representing the kills resulting through attack by each of two or more species. It was going to be necessary, they said, to combine these several aggregates in a different manner. Thus a 50% parasitism of the eggs if it could possibly be secured, followed by another 50% parasitism of the caterpillars, could not by any possibility be considered as resulting in 100% parasitism or complete extinction but only in 50% parasitism added to 50% of what remained which amounted in effectto 25% of the whole. In this manner an aggregate of 75% only is secured. They said further that any specific amount of parasitism as 20% of the eggs, was neither more nor less, but exactly as effective as 20% parasitism of the caterpillars and pupae, in so far as its value in constructing the final aggregate was concerned. The principle they thus established, though it may seem obvious enough, had not apparently been previously recognized by workers on biological control and it is of the very greatest importance.

We have had some good illusuations of different approaches to the study of forest insects. The subject has by no means been exhausted-the physiological approach, for instance, has been barely touched on—but I think the point has been brought out that there is no essential difference between the problems and methods of forest entomology and, say, agricultural entomology. There may be some differences in emphasis–the nature of the forest crop encourages the long-term ecological approach–but even this difference seems to be disappearing, as may he illustrated by Dr. Glen's recent paper on factors governing the abundance of insects.

In the come of the study of parasites of mealybugs for introduction into West Africa for the control of mealybug vectors of cocoa virus a number of undescribed Encyrtids have been discovered in Trinidad, B.W.I. Descriptions of these and new Encyrtids reared from other hosts will be published in a series of papers.

The present paper records three species of Pseudaphycus from Trinidad, two of which are described as new. I am indebted to Mr. H. Compere who stated (in litt.) that the species herein described were probably new and pointed out the characters that separated them from related species. Dr. B. D. Burks kindly compared specimens of these species with types of related species deposited in the United States National Museum and suggested slight alterations in the manuscript which have been duly made.

The following records of Canadian Siphonaptera are supplementary to those detailed in Fox (1940), Ewing and Fox (1943), and Holland (1949, 1952). Records of fleas from the Maritime Provinces are particularly lacking in the literature, being limited to the following species:

NEW BRUNSWICK: Ceratophyllus gallinae (Schrank); Epitedia wenmanni wenmanni (Rothschild); Hoplopsyllus glacialis lynx (Baker); Nearctopsylla genalis laurentina Jordan and Rothschild; Orchopeas caedens durus (Jordan); Oropsylla arctomys (Baker); Stenoponia americana (Baker).

During the period April 13 to November 10, 1953 the writer conducted a survey of calyptrate flies of medical importance at London, Ontario, and its vicinity. The flies were trapped in twelve traps baited wit11 malt extract and set out in twelve localities such as garbage dumps, the border of swamps and the premises of meat packing plants, sewage disposal plants, dairies, restaurants and industrial properties. During the course of the survey 142,975 flies in the families Anthomyiidae, Muscidae, Calliphoridae and Sarcophagidae were collected. From these were chosen twenty species for counting. The daily catch of these flies from each of the twelve traps was kept separate and the flies were sorted according to species and sex and a record was kept of the numbers of each species captured in each trap. Tn making the identifications it was necessary to examine each specimen under a binocular microscope and during this process the specimen was also examined for the presence on it of parasites or other organisms clinging to it. Three such organisms mere found on several flies: mites, pollinia of milkweed and fungi of the genus Empusa.

In Vol. 87, p. 256, captions for Figs. 13 and 15 should be reversed, p. 261, line 5, (Fig. 30) should be (Fig. 16), line 6 (Figs. 11, 12) should be (Figs. 19, 20), line 7, (Fig. 3) should be (Fig. 26).

Difficulties experienced in rearing Feralia spp. beyond the pupal stage, and inability to distinguish species in the immature forms, has led to a study of their larvae and pupae. So far no specific differences have been observed in the larvae but progress has been made in the identification of Feralia in the pupal stage.

Attempts to rear plants and animals under aseptic conditions have led to the development of special cabinets in which the atmosphere can be sterilized and the experimental materials manipulated without fear of contamination. The mechanical design, instrumentation, and principles upon which the development of such equipment is based have been admirably discussed by Reyniers (1943). House and Patton (1949) made an ingenious modification of Reyniers' cabinet whereby it can be used to anaesthetize, handle, and weigh cockroaches aseptically.

In line 4 of first paragraph, p. 210, Vol. 87, for “New England” read “New Zealand”.

The mailing date of the July 1955 number was erroneously given as July 15, 1955. This should be changed to August 26, 1955.