The following is a summary of our studies on population of head lice, adults and nits.1. Out of a total of 8702 adult lice, the male population comprised 2031. The gross infestation rate per head was 129.9 and the maximum number found on a single head was 1434. A disproportion in the distribution of the two sexes was a marked feature.2. Patients below the age of 11 showed a lower infestation rate than those above this age, and short-haired individuals were more heavily infested than long-haired ones.3. Frequent combing of the hair and the use of oil did not seem to dislodge the adults or to prevent the females from laying eggs.4. The maximum larval count on a single head was found to be 4260, the average number of larvae per single head was 418·8, and 9 to 1 was the maximum proportion of larvae to females.5. The maximum number of nits on a single hair was found to be 17 and 5·06 was calculated as the average number per hair.6. Treatment with kerosene and pyrethrum killed all the lice and nits, and reinfestation did not occur.7. The infestation did not spread to healthy patients in the hospital ward; it is thought that the poor migratory habits of lice are responsible for this.8. From studies on the reinfestation of an individual after treatment it is concluded that head-lice cannot establish themselves on any part of the body except the head, and if their access to the head is prevented, the lice will not survive for more than 24 hr.

p m a~ crop. 11. Aphis survey; its beating upon the selechoo of districts for 6&d potato production; A m -(1935"). Studies on aphides infesting the potato Bid crop. 111. Efiect of variation in rektive b h d i t y on the flight of M y w pm;oC (Sulz.). Am. oppl. Bid. LAPIG, F. (199). A new tphid pert of VIdetS. EiU. 22.106. M a Mw. 6 9 . 9 . -(19356). Studies on aphides infesting the potato LOUGHN-J. B. (1939). M r p u a vector of crop. IV. Notes on the *tion md condition of llste potpto vlrusca N -, 4 November. M y w S T -, L. N. (1932). .Notes oo a n e~ -hid pea -(1936). Studies on aphides infesting tk p"" of viokrs. 9th An Rcp. -2. PIant Path. seolccrop. V. Laboratory experiments on tbc dfcd of wmd Hqvm? A&. CoUqe.

Pediobius imbreus (Walker), a hyperparasite of Opisina arenosella, is distributed throughout Kerala. The biology of this hyperparasite was studied in the laboratory. The mating process took, on an average, 43 sec. The female started to lay eggs on the same day of emergence and laid upto 30 eggs in her life time.The eggs hatch after 36 to 40 h. of incubation. There were three larval stages. The duration of the immature stages from egg to adult emergence was completed in 412 to 420 h, and was dependent on temperature.

In order to determine the method of entry of a contact insecticide such as pyrethrum into the body of an insect, studies were undertaken which showed that:—(a) The rapid penetration of the insecticide into the body cannot be effected through the cuticle.(b) When a mosquito has been sprayed with a mixture of pyrethrum extract and oleic acid, the deposition of fat globules around the tracheal trunks is a characteristic feature; this suggests that rapid diffusion of the insecticide takes place through the tracheal wall.(c) Experiments on flies with their spiracles closed indicate that the absorption of pyrethrum, either in the liquid and powdered states, was very slow. This fact indicates that normally pyrethrum enters the body through the spiracle.

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