STUDIES ON PLANT CUTICLE: THE CUTIN COMPONENT OF THE CUTICLES OF LEAVES

Methods are described for the chemical separation from leaf material of the ventral and dorsal surface cuticular membranes and for the determination of cutin in the membranes and leaf tissues.
The cutin contents of the cuticular membranes separated from leaves of laurel, rhododendron, and Euonymus , and of leaf tissues of cauliflower, red beet, banana, tomato, strawberry and blackcurrant are reported. The relationship between the cutin and waxy components of the leaf cuticle is discussed, and earlier work on the development, structure and chemistry of the cuticle is reviewed.     

CUTICLES OF TWO SPECIES OF ALETHOPTERIS

Specimens of Alethopteris sullivanti (Lesquereux) Schimper and Alethopteris lesqueieuxi Wagner were found in Middle Pennsylvanian coal balls from the Lovilia, Iowa and West Mineral, Kansas localities. Light microscopy and scanning electron microscopy (SEM) were used to study macerated cuticles of these two foliage types of the pteridosperm, Medullosa. The lower epidermises of both species of Alethopteris possess sunken stomata, papillae, and evidence of multicellular hairs. The upper epidermises are devoid of these features. Critical point drying and subsequent observation with SEM were used to document the structure of the multicellular hairs of A. lesquereuxi. Replicas of the lower epidermal features of an impression-compression specimen of A. sullivanti were observed with SEM and compared with the petrified specimens.     

THE STRUCTURE OF INSECT VIRUS PARTICLES

Thin sections have been cut of the virus particles from four types of insect virus diseases: cytoplasmic polyhedroses of lepidopterous larvae, a nuclear polyhedrosis of Tipula paludosa (Diptera), a granulosis from Melanchra persicariae (Lepidoptera), and a new virus disease without polyhedra from T. paludosa. The cytoplasmic polyhedral viruses are thought to have composite particles in some cases. The shape and enveloping membranes of the different virus particles are compared. In the new virus disease of T. paludosa some of the virus particles appear to be empty; inclusion bodies surrounded by complicated membranes are also demonstrated.     

昆虫种群的生态适应

体外的自然选择作用是达尔文讨论的自然选择的主体,此种选择是通过生物所处的有机的和无机的外界环境条件起作用。实验证明,外界环境条件不仅起着筛选生物变异的作用,它本身亦是导致生物产生不定变异的外在诱变条件,推动生物适应它所在的环境。     

中国昆虫毒理学、昆虫病理学三十年

化学防治是解决害虫问题最为有效的手段之一,三十年来曾对杀虫药剂和毒理学做了不少的科学研究。据统计,《昆虫学报》发表的有关论文在第一个十年中占总篇数的9％,反映我国对害虫的化学防治在早期已有一定的基础。然而,最早试验用昆虫病原防治害虫开始于五十年代中期,对于昆虫病毒的研究开始于六十年代,所以昆虫病理学在我国的开展较晚。这两门能密切结合生产实践的昆虫学分支学科的内容和在我国发展的过程不同,宜加以分述。     

中国昆虫分类学、昆虫形态学三十年

欣逢中华人民共和国成立三十周年,举国欢腾,同申庆祝！三十年来在中国共产党领导下,科学工作欣欣向荣,做出了不少成绩,与解放前相比,各门学科都有长足进步。我国古代昆虫学知识可以追溯很远,有许多光辉业绩。近代昆虫学则自本世纪第十年代开始,共约七十年历程,前四十年在旧社会艰苦环境中渡过,近三十年才获新生。许多年长的昆虫学者,今还健在,记忆犹新。抚新追昔,精神倍增,今后培养更多的人才,形成一支坚强队伍,向国际昆虫学先进水平进军,必将做出更大更多的成就。我国地大物博,人才辈出,对于这种预期,一定可以实现。     

THE PENETRATION OF THE INSECT CUTICLE BY ISOMERS OF BENZENE HEXACHLORIDE

The penetration of the α-, β-, γ- and δ-isomers of benzene hexachloride through the insect cuticle has been studied by a micro-colorimetric technique.
Grain weevils were exposed for varying periods to deposits of pure isomers of benzene hexachloride on filter-paper. The amounts of each isomer picked up by the insects were determined as two fractions, one 'outside' representing that which could be removed by cold methanol washing, and the other 'inside' recovered after decomposing the insects with nitric acid.
The results show that the amounts of each isomer taken up by the insects are in the approximate ratio of their solubilities in hydrocarbon solvents, and that the y-isomer penetrates through the outer layers of the insect integument much more rapidly than the other three isomers tested.
On the basis of these results it is concluded: (i) that the first stage of pick-up of insecticide by the insects is simple solution of the insecticide in the outer waxy covering of the epicuticle; and (ii) that structural effects play an important part in the penetration through the insect cuticle as well as in toxic effects at the site of action.     

THE RESISTANCE OF INSECT PARASITOIDS TO THE DEFENCE REACTIONS OF THEIR HOSTS

Some of the following propositions are to be read as suggestions or hypotheses, supported by circumstantial or direct evidence, but not yet rigorously demonstrated. An estimate of the significance to be attached to each should be gathered from the body of the paper rather than from the following brief statements. 1.The problem is posed: how do endophagous parasitoids counteract the haemocytic defence reactions of their usual hosts? 2.It has been demonstrated that the egg and young first-instar larva of Nemeritis canescens have a coating on their surface which enables them to escape the attention of the haemocytes of their usual host, and to develop without exciting a defence reaction. The coating is applied to the egg before it is laid, and to the cuticle of the larva before it hatches. A little evidence suggests that some other ichneumon wasps of the subfamily Ophioninae may use this mechanism of resistance. 3.Older first-instar larvae, and the second and later instars, of many parasitoids, both hymenopterous and dipterous, probably overcome the haemocytic reaction of their host by rapid feeding, which depletes its blood both of cells and of nutrients, and so drains its resources that haematopoiesis is prevented and encapsulation becomes impossible. 4.The common habit of parasitoids of lingering in the first instar, before ingesting much food, while the host goes on developing to another stage or undergoes diapause, may enable the larva to retain a protective coating that would have become ineffective if it had grown. When at length the larva does feed and grow, the preceding mechanism (3) comes into play. 5.The teratocytes and pseudogerms formed by many species in several families of Hymenoptera absorb nutrients on a large scale from the blood of the host. They act quickly, as soon as the larva hatches. I suggest that by their attrition of the host's reserves of food, and its consequent debility, they prevent an effective haemocytic reaction to the young parasitoid. 6.Some dipterous and hymenopterous parasitoids first inhabit the intestine of their host, and do not penetrate the body cavity until they are ready to overwhelm the defence reactions by rapid and gross feeding. 7.Parasitoids that live temporarily inside an organ of the host may there acquire a coating which protects them from reaction by the blood cells. 8.Species of parasitoids that occupy an organ of the host for a long period, and develop inside it, escape a defence reaction because they live within the connective tissue covering the organ, to which the blood cells do not react. 9.Eggs of hymenopterous parasitoids laid within the embryos of their hosts may be treated by the embryonic blood cells as a developing organ, and become covered with connective tissue as those organs are. Thereafter they would not be recognized as foreign bodies. 10.Parasitoid eggs laid in the eggs or the young larvae of their host may be coated with host substances, or covered by connective tissue (9), before the blood of the host be comes capable of vigorousdefence reactions. They would there after escape recognition as foreign bodies. This may be the advantage of the habit of the so-called egg-larval parasitoids. 11.Reasons have been given by Schneider (1950) for his belief that the serosa of the ichneumon wasp Diplazon fissorius secretes something that locally inhibits the defence reactions of its hosts. The trophamnion and pseudoserosa of some parasitoid eggs may have this function. 12. Some parasitoids, especially second- and third-instar larvae of Tachinidae, physically repulse the haemocytes of their host, moulding them into a capsule that serves the maggot as a respiratory sheath.