216 



aldehydes and acids are positively chemotropic in products of fermen- 

 tation, so far as amyl compounds are concerned. AlcolioLs, aldehydes 

 and acids containing the methyl group CHg are positively chemotropic, 

 except in cases where their molecular weight is about 30 (meihyl 

 alcohol) or below, the chemotropic stimulus being aggravated where the 

 methyl group is augmented by union with (CH^)^.. Compounds 

 containing the benzene ring are unattractive, though not necessarily 

 negative (repellent). These are unsaturated. Amyl compounds 

 are probably increasingly attractive in the order in which they are 

 formed during fermentation and decomposition. It is possible that 

 the aldehyde group, in all compounds containing it, is to a certain 

 extent negatively chemotropic. There is no relation between volatility 

 and chemotropic action. 



It may be pointed out that saturated compounds contained in fer- 

 menting vegetable substances and containing the molecular group 

 CHg (CHo)^, may constitute the source by which the house-fly is guided 

 to its food. 



Experiments with essential oils indicated that in general they are 

 unattractive, certain of them being inactive, while others evoke 

 negatively chemotropic stimuli. During evaporation the repellent 

 action passes ofi. 



A record of other insects observed during the experiments showed 

 that the stimuli are not the same for all insects. 



Ii^NCA(C.). La Flagellose des Euphorbes. [FlageWosis oi Euphorbia.] 

 — Ann. Inst. Pasteur, Paris, xxxiv, no. 7, July 1920, pp. 432-465, 

 2 plates. [Received 4th October 1920.] 



The morphology and development of a flagellate, Leptomonas davidi, 

 in the latex of Euphorbia are discussed. In Portugal the transmitting 

 agent is Stenocephalus agilis. Scop. [R.A.E., B, viii, 17]. 



This Coreid bug was discovered with some difficulty, as it hides under 

 dry leaves during the day and only goes to Euphorbia at night. It 

 is most abundant in July and August ; mating takes place in those 

 months, when the females, which predominate, nearly all have mature 

 eggs. Oviposition does not seem to occur on Euphorbia. The young 

 forms appear in August. Stenocephahis appears to be exclubively 

 phytophagous. In Portugal it feeds on the latex of Euphorbia peplus 

 and E. segetalis and has not been noticed on any other plants. After 

 sucking in one place the bug begias at another, this fact explaining 

 the numerous punctures. 



The evolution of the flagellabe in the insect is also dealt with. The 

 Leptomonads multiply by division. From the fourth day of infection 

 they increase in size, and giant forms occur, such as are not seen in the 

 latex. Between the fourth and eighth days very minute forms, quite 

 different from those previously seen, appear. These parasites occur 

 throughout the digestive apparatus, and later invade the salivary 

 glands. They are evidently the infective forms. It would appear 

 that the developmental cycle of L. davidi is confined to the bug and 

 the plant, and that transmission from one bug to another must be 

 rare. S. agilis is not only a vector, it is the animal and primitive 

 host of L. davidi. 



