Concerning the light reactions of the adults, it may be noted that males are photopositive when in a dark-adapted state, but they rapidly become adapted to any light intensity and become extremely sluggish. Females in the dark-adapted state exbihit either photonegative behaviour or compassing behaviour, with no evidence that there is any orderly transition from one type of behaviour to the other. Light-compass orientation of flying females makes it possible to collect some at light traps, despite their normally negative response.

In the first paper of this series (5) the ecologica1 approach to apple orchard insect problems was discussed and it was pointed out that the spray program must be considered as an ecological factor. It is obvious that because of the complex relationships of the plant and animal species in an orchard it is impossible to change the relationships of any single species without, in greatcr or lesser degree, altering the whole community. In some cases the disturbed relationship may show immediately in the repression of one pest and the rise of another, while in other cases the changes are much more obscure and the economic effects nlay not appear for a long time. The cause of these change is that a spray aimed at some particular species also, directly or indirectly, aifects many other species in the orchard environment and thus may be expected to alter the numerical relationship of many predacious and parasitic forms to certain pests or potential pests which are their prey. The oystershell scale, Lepidosaphes ulmi (L.), and the European red mite, Metatetranychus ulmi (Koch) = (Paratetranychus pilosus (C & F)) are examples of species which react quickly to changes in spray treatments owing to the large populations they may build up in a short time and to the rapid increase of their predators and parasites when not hindered by the spray treatments.

Machaerilaemus Harrison: Parasitology, VII, p. 389 (1915).

Machaerilaemus Harrison: Harrison, Parasitology, IX, p. 60 (1916)

Hirundoecus Ewing: Proc. U. S. N. M., LXXVII, Art. 20, p. 12 (1931).

Machaerilaemus Harrison: Bedford, 18th Rept. Dir. Vet. Serv. and Anim. Ind. Un. S. Africa, p. 377 (1932).

Hirundoecus Ewing: Bedford, ibid, p. 380.

It is generally considered that the smaller the particle size of insecticides applied as solids, the greater is their effectiveness. Smith and Goodhue (1) arrived at his conclusion after a review of the literature. Woodruff and Turner (4) showed that decrease in particle size of DDT wettable powders increased the toxicity of the residues against house flies, and that correspondingly better results were obtained from the residues of smallest particle size in a field test against potato leafhopper and fleabeetles. Steiner et al. (2), who have done much work on the effect of DDT particle size on codling moth control, stated that for this purpose the optimum surface mean particle diameter for DDT lies between 2.5 and 5 microns.

The literature dealing with the methods by which the larvae and adults of tachinid parasites escape from sawfly cocoons indicates in certain cases that only circumstantial evidence is available concerning the formation of the exit hole in nature. Among these parasites a large number leave their hosts while the sawflies are in the larval stages. The larvae make their escape as mature maggots through a hole gnawed in the soft host integument. A few species, however, continue to develop within the host after the host cocoon has been formed. Some of these cut through the cocoon as mature larvae and later pupate in a suitable medium, while others form their puparial cases within the host cocoons, the adults later escaping from both the puparial cases and from the sawfly cocoons. The only escape mcchanism possessed by an adult tachinid fly consists ot the alternate expansion and contraction of the ptilinum against the surrounding wall. Since the cocoon is usually quite tough and leathery it is essential that some provision be made in advance to enable the adult to escape. This seemed to occur with adults of Phorocera hamata A. and W. which emerge from their puparia within the host cocoon and then escape from the cocoon proper, leaving a characteristic round cap which appears to have been cut (Fig. 1, C). The method of formation of this cap has been the subject of discussion by several authors.

For some years it has been evident to workers conducting research on grasshopper control methods that those dead grasshoppers which can be found at the scene of application of a control measure do not necessarily represent all the grasshoppers which have succumbed to the treatment. Often, dismembered remains are considerably in evidence and usually only the more resistant parts, such as head capsules, remain to be found. It is reasonable to suppose that many of the dead bodies of grasshoppers may disappear entirely, before sufficient time has elapsed for the final observations on the treatment. It is important, therefore, in relation to the appraisal of the efficiency of control measures in the field, such as baiting, to know to what extent this is true. It is particularly important in the study of baits because, where arsenites are used, at least three days may be required for the poison to take full effect after ingestion and before the appraisal can be made. Meanwhile, a considerable period of time has elapsed during which grasshoppers that died 1 or 2 days after feeding could be removed. Under these circumstances it would obviously be erroneous in appraising the results, to take into consideration only the counts or estimates of numbers of dead on the ground, particularly if compared with the estimated population prior to baiting.

In a previous paper (Simmonds 1946) a curious factor affecting diapause in insects was recorded. In two species of parasitic Hymenoptera the age of the parent female at the time of oviposition has a marked effect on the tendency of the resulting larva to enter a state of diapause when full-grown. The older the female at the time of oviposition the greater is the chance that an egg will produce a larva entering diapause. In a second paper (Simmonds 1948) this maternal influence on the tendencies of her progeny to enter diapause was investigated further. Some general conclusions were drawn as to the nature of diapause, and the experiments were considered in the light of the various theories put forward to explain the phenomenon. In brief it was concluded that the underlying cause of diapause is the occurrence of a physiological disturbance at some stage in the life-history.

This paper presents descriptions of three new species of Ephemeroptera from Illinois, all belonging to the genus Ephemerella. These are forms segregated from material in the Illinois Natural History Survey collection; the types are deposited in that collection. Two of these species are closely related to the genotype, E. excrucians Walsh, and it was thought for some time that one or the other of them would prove to be that species. Study of the lectotype of excrucians showed, however, that both of these species are recognizably distinct from excrucians.

During the summer of 1946 specimens of anobiid beetles were received from G. Stace Smith of Creston, British Columbia, for identification. Mr. Smith believed that the specimens represented a new species and requested that the species be described.

This species resembles the European Xestobium rufovillosum DeGeer so closely that they can only be separated with great difficulty, but the habits of the two species are entirely different.