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.

Much confusion has arisen in the past with regard to the correct application of the names of certain Pyralid rice borers; I hope the following notes and illustrations will clarify the position.

The Onion Fly (Delia antiqua (Mg.)) was bred at Wye, Kent, under insectary and laboratory conditions to obtain further information on its biology and reactions to various temperatures.

A comparison of the times of emergence of overwintering generations of Onion Fly and Cabbage Root Fly (Erioischia brassicae (Bch.)) in an insectary showed that the former emerged consistently about a month later than the latter. This supported the observations of previous workers that the Onion Fly was not active in the field until late May.

A diet containing protein was necessary for oviposition. The length of the preoviposition period was affected by temperature. Flies maintained at 25°C. laid eggs in 10–24 days, with an average of 15 days. At spring and summer laboratory temperatures (12–29°C.) the preoviposition period was 10–25 days, with an average of 15 days; and in autumn and winter (11–20°) it was 11–46 days with an average of 21 days. Flies maintained at 6–8° did not lay eggs.

Flies in captivity laid up to 123 eggs at the rate of 1–45 per day. Intervals between batches of eggs varied from 1–9 days, and the oviposition period was 7–25 days. Flies lived up to 6 days after oviposition.

The incubation period depended on the temperature. Eggs at 25°C. hatched in 2 days; at 20° in 3–4 days; at 15° in 4–6 days; and at 7–10° in 9–14 days.

The temperature also affected the duration of larval and pupal stages. At 25°C. the successive larval stadia required 2, 2 and 5–9 days, respectively. Lowering the temperature increased the time for development until at 9–11° the three larval stadia required 8–12, 8–18 and 24–37 days, respectively. At 25° the pupal stage lasted 12–17 days; at 20° it was 16–25 days, and at 15° it was from 35 days to over a year. At 25–30° the development from egg to adult was completed in 25 days; at 25° it required 28 days; at 22–27°, 30 days; at 19–24°, 33 days.

At 25°C. the Onion Fly bred continuously without diapause. When larvae were reared at temperatures below about 18° pupal development was often retarded. Pupae formed from larvae reared at 12–18° and maintained at approximately that temperature, required 94–442 days to complete their development. By raising the temperature of pupae formed from larvae reared below 18°, it was demonstrated that a true diapause had been induced. Of 54 pupae raised to 25°, 8 (15%) completed their development in the expected time (13–16 days) and 46 (85%) required 94–208 days. Of 322 pupae formed from larvae reared in an insectary in May and June at 10–18° and exposed to July temperatures of 13–20°, 37 (11%) emerged in 25–35 days and 252 (78%) required 234–294 days. Similarly, of 283 pupae formed from larvae reared at 12–21° and exposed to a temperature of 15–23°, 30 (11%) completed their development in 21–31 days while 253 (89%) required 118–341 days. Exposure to low temperatures was not necessary to terminate pupal diapause.

An examination was made of the movements of Pscudococcus njalensis Laing, the dominant vector of swollen-shoot disease, on cacao in Ghana. The mobile population is composed almost entirely of first-instar nymphs (92%). Movement is initiated at about 23·5°C. and activity becomes more pronounced at higher temperatures. Movement is maximal during mid-afternoon when many hundreds of insects become mobile on heavily infested trees. The density of mobile mealybugs increases from the base of the trunk and reaches a maximum at a few feet below the top of the canopy. Under experimental conditions, nymphs walked at least 28 ft. in search of favourable feeding sites and their dispersion increased proportionately with the number of canopy bridges. On cacao, adults are occasionally carried by the ant, Crematogaster striatula, Emery.

Using insects labelled with radioactive phosphorus, the assumption was confirmed that P. njalensis is capable of walking from tree to tree via the canopies of farmers' cacao. In a plantation of 8-year-old Amelonado cacao, 40 per cent, of the branches were in contact at 4-ft. spacing and about 20 per cent, at spacings between 5 and 7½ ft. No branches were in contact where the trees were spaced more than 12 ft. apart. At the closest spacing, the ratio between the number of mobile mealybugs that reached adjacent contact trees and those that did not was about 9:100, this ratio being reduced to 1 or 2:100 amongst trees growing 5 to 7½ ft. apart.

The significance of the movement of mealybugs in the canopy in relation to virus spread is emphasised. Methods of preventing vector dispersal by pruning, wide spacing and interplanting with a secondary tree crop are discussed. The importance of a closed canopy in preventing attack on the trees by Miridae is stressed.

An experiment was designed to ascertain the maximum yield of adults of the Cigarette Beetle, Lasioderma serricorne (F.) that could be reared from a given quantity of foodstuff. Equal numbers of eggs of this species were added to batches of tubes containing different weights of wheatfeed, and the resulting adults were removed, counted and weighed.

The weights of wheatfeed had been chosen so that in some of the batches of tubes it would not be completely exploited. When emergence of adults was complete, further numbers of eggs, which were calculated to produce approximately the number of larvae necessary to complete the process in each batch of tubes, were then added, and the resulting adults again removed, counted and weighed.

The maximum biomass (wet weight) of adults of L. serricorne which could be reared from egg to adult per gramme of wheatfeed at 25°C. and 70 per cent. relative humidity was found to be 0.214 g. (108 to 129 specimens, all more or less undersized, and many with a retarded rate of development, compared with insects given ample food). In addition to the 21 per cent, of the food converted into adult insects, another 27 per cent. by weight of the original foodstuff was lost, presumably as water and carbon dioxide, leaving just over 50 per cent. undigested residue, most of which was faecal matter that would have passed through the insects at least once.

The yield of insects per g. loss of weight of the foodstuff was 0.46 g. (wet weights), which is very close to the corresponding figures calculated from the results of Fraenkel & Blewett for Dermestes maculatus Deg., Tribolium confusum Duv. and Ephestia Kuehniella Zell. on various foods, but three times as great as the corresponding figure calculated from Richards' results for Calandra granaria (L.) in wheat.

There was evidence suggesting that a truly maximal yield (slightly greater than in these experiments) might be attained by adding an optimal number of eggs to the food at the start, instead of adding a second population to an incompletely exploited food supply.