Métamorphose de l'intestin antérieur et de l'intestin moyen chez Tenebrio molitor L. (Insecte, Coléoptère)

The foregut and midgut of male and female Tenebrio molitor were studied just before and during metamorphosis. Three successive stages can be recognized by characteristic features of the cuticle and epithelium of the foregut, and of the peritrophic sheath, epithelium, basal lamina, and muscular connective sheath of the midgut. In the external integument, changes occur during two periods, implying two reprogramming phases. Overall, periods of change for the gut are concomitant with first the pupal molt and then the imaginal molt. However, in the foregut, cuticular secretion begins later than in the integument and is completed at the time of ecdysis. For the midgut, imaginal differentiation is slow and ends a few days after ecdysis.

Effects of juvenoids on the Mediterranean fruit fly, Ceratitis capitata (Wied.) (Diptera, Tephritidae)

Screening of 38 selected juvenoids on Ceratitis capitata (Wied.) revealed that several aromatic compounds, mostly ethers of 6,7-epoxygeraniol and of 6,7-epoxycitronellol, inhibited hatching when administered to freshly laid eggs as 0·1% acetone solution. Application of juvenoids within 24 h before and after puparium formation caused disturbances in imaginal differentiation. Treated insects developed either into pupa-adult intermediates failing to emerge or into defective adults whose fecundity was severely decreased. Both earlier and later applications of juvenoids were less effective. The most active compound in topical assay on fully grown larvae was ethyl 10,11-epoxy-5-oxa-3,7,11-trimethyl-2-dodecenoate, which inhibited emergence of 50% of treated insects at 0·01 μg/specimen and caused external deformities in 50% of emerged adults at 0·00001 μ/g/specimen. Four other aliphatic compounds (methyl 11-methoxy-3,7,11-trimethyl-2,6-dodecadienoate; ethyl 11-methoxy-3,7,11-trimethyl-2-dodecenoate; isopropyl 3,7,11-trimethyl-2,4-dodecadienoate; and isopropyl 11-methoxy-3,7,11-trimethyl-2, 4-dodecadienoate) and l-ethyl-4[(6,7-epoxy-3,7-dimethyloctyl)oxy] benzene were about five times less active. A concentration of 33 parts /106 of ethyl 10,ll-epoxy-5-oxa-3,7,11-trimethyl-2-dodecenoate in larval food caused deformities in 60% of emerged adults.

Natural and synthetic materials with insect hormone activity

The juvenile hormone of insects is known to inhibit the process of insect metamorphosis. It is also known to stimulate ovarian growth in adult females of some species. It has been found recently that some substances with juvenile hormone activity also influence embryonic development. In the bug Pyrrhocoris apterus such substances, which prevent imaginal differentiation in metamorphosis, also affect the differentiation process of embryos at a certain stage of egg development (Sláma & Williams, 1966). This has been confirmed with other juvenile hormone analogues on embryonic development of silkworm eggs (Riddiford & Williams, 1967) and grasshoppers (Novák, 1967). According to the above observations eggs treated with the substances show abnormal development of the embryos, which may pass successfully through the early stages of embryogenesis but are unable to complete differentiation. Usually the embryos do not develop beyond the stage of blastokinesis and die within the egg shells.