1. Plutella maculipennis, Curt., a widespread Lepidopterous pest of Brassica was introduced into New Zealand about sixty years ago. In most countries a high degree of natural control is maintained, but in New Zealand the moth population is permanently maintained at a high level. Investigation showed that in New Zealand there were no natural enemies of importance, while in other areas these are constantly associated with Plutella.

2. The distribution of the moth throughout the world is exceedingly wide, but in England it only occasionally reaches pest proportions.

3. Preliminary work indicated that two Campoplegines, Angitia cerophaga and A. fenestralis, constantly parasitized large numbers of the Plutella larvae. Initial efforts were devoted to collecting and breeding a large supply of these in England for introduction into New Zealand as controlling agents.

4. From several thousand specimens of Plutella, fourteen species of parasites were recovered, of which eight were hyperparasites. The only parasites which were numerically important were the two parasites, Angitia cerophaga and A. fenestralis. Their efficiency is not impaired to any appreciable extent by hyperparasites. A key showing the diagnostic differences of the parasites and hyperparasites of Plutella is given.

5. These two species of Angitia are commonly recorded as parasites of Plutella throughout the world, although under different names. A large quantity was bred in the laboratory and despatched to New Zealand after overcoming certain difficulties connected with transport. It appears that both species of parasite must overwinter in other hosts than Plutella.

6. Certain experiments were performed in an endeavour to assess some of the effects of climate. The upper limiting temperature of Plutella is approximately 40°C. and the lower limit for breeding purposes about 10°C. All stages of the moth can survive short periods of cold greater than 10°C., but it is believed that hibernation is normally accomplished in the adult stage. As the immature stages of the moth live in a specialised microclimate of high humidity, changes in the moisture content of the general atmosphere have little effect. Rain, if appearing at certain critical times in the life-cycle, may be a controlling agent.

7. The most favourable areas for multiplication of the moth appear to be in the sub-tropics and warmer temperate zones. It is suggested that Plutella originated in the Mediteranean region.

8. Even in the cooler temperate countries the climate would allow an indefinite increase in the moth. It is believed that an effective check on this multiplication is supplied by parasites.

9. As the climate of England and New Zealand are essentially similar there is reason to suppose that the introduction of parasites from the former country will lead to eventual control being obtained in New Zealand.

Pineus pini has been introduced by accident into Australia and has become a pest of some importance on Pinus radiata and P. pinaster and also attacks a few other species.

Recent developments of physiology have emphasised the importance of membranes, and in entomology, studies on the permeability of membranes would offer the necessary basis for investigations on the physiological action of insecticides, particularly those applied externally, as well as on the many aspects of insect physiology.

Die folgenden Beschreibungen beziehen sich auf die Tachiniden (s. 1.), welche ich vom Imperial Institute of Entomology in London zum Bestimmen erhielt. Für die Zusendung dieses sehr wertvollen und schönen Materials möchte ich auch an dieser Stelle dem Herrn Direktor Sir Guy A. K. Marshall meinen Dank aussprechen.

This paper is the outcome of an attempt to identify certain species of Braconidae received from the Forest Research Institute, Dehra Dun. The material comprises parasites of various Lepidopterous pests defoliating teak, shisham and deodar. Three of them are dealt with in the following pages ; the others will be discussed in a later paper.

General Growth.

Generally, females have higher rates of growth than males. The phases, however, do not show appreciable differences in the rate. The pronotum has for increase in length the highest values which decrease throughout the instars (whereas the constants for the other parts remain fairly stable up to the fifth instar).

Dyar's rule was applied for the growth in length of the middle femur and the width of the head, and it was found that the rule holds good for these parts.

Przibram's rule, as modified by Bodenheimer, holds true for the growth in length of the different parts and shows the occurrence of latent cell-divisions varying from one (width of head and of pronotum) to four (length of pronotum). The number of latent cell-divisions keeps fairly constant in both phases.

For wet weight Przibram's principle is inapplicable, owing to the large percentage of differences between the actual and calculated values.

Gregarious males are heavier than solitary males up to the third stadium ; gregarious females are heavier than solitary females up to the third stadium ; fourth, fifth and adult stadia being characterized by higher values in wet weight for solitary females than for gregarious females. Females have higher rates of increase in wet weight than males. No significant differences exist in the rates of increase between gregarious and solitary individuals. In the fifth-adult stadium all the rates decrease except in gregarious females, which show a rise.

Gregarious insects have higher values in dry weight than solitary insects, except solitary females in the adult stadium. The coefficients are higher for females than for males.

The rates of increase reach the highest values in the second-third stadium of gregarious insects and solitary females, whereas solitary males have their highest value in the fourth-fifth stadium.

With the exception of solitary females, all the rates of growth in dry weight decline in the fifth-adult stadium.

The rates of growth of the hind legs obtained from the cube-roots of their wet weights are compared with the rates of linear growth of the hind femora. Their variation throughout the instars seems to be in opposite directions. Therefore it is suggested that the rates of growth in wet weight of the hind legs and the rates of growth in length of the respective hind femora are independent of each other.

Growth of the parts.

The application of the exponential allometry formula y=bxα to the data on dimensions of the parts of Locusta shows the existence of negative, positive and almost isometric growth.

The pronotum has the highest value for the growth in length relatively to the growth in length of the middle femur ; the lowest value pertains to the growth in width of the head.

Males have higher values than females ; phase gregaria exhibits higher growth-ratios than phase solitaria.

With the exception of the hind femur the growth-ratios decline throughout the instars. The greatest decline pertains to the growth in length of the pronotum.

A growth-gradient exists in Locusta with the highest value in the pronotum. The middle femur divides the growth-gradient into two parts : an anterior part with values decreasing with the growth of the insect, and a posterior part whose values increase with its growth.

Effects of the amputation of the hind tibiae on crowded locusts.

The effects obtained by mutilating both hind tibiae of three hundred first instar hoppers of Locusta migratoria migratorioides and placing them in a crowded condition are compared with the effects obtained by crowding a batch of the same number of first instar unoperated insects.

The insects with their hind tibiae cut off did not develop as far as those of the control batch ; the differences in dimensions are greater for the hind femur than for the other parts of the body.

In the experimental batch the hind femur, as a consequence of its useless condition, became extremely short as compared with the elytra, bringing the ratio E/F to a high value (over 1·950), thus leading to a false interpretation.

The occurrence of the black-orange coloration in both batches suggested that both developed towards phase gregaria. This coloration was stronger and more uniform in the control batch than it was in the experimental batch. Thus the control animals developed into a better gregarious type.