1940: Entomology

Malaria Mosquitoes.

That malaria mosquitoes in the Tennessee Valley spend the winter in hibernation was reported by Drs. E. H. Hinman and H. S. Hurlbut of the Tennessee Valley Authority. The specimens they found in their investigations were all adult females that had mated. Hence, they were ready to lay eggs as soon as warm weather permitted. These workers also report that the hibernating females in caves have survived as long as 69 days without food with the temperature ranging from 51.5° to 59° F.

Protection of Crops by Insects.

Moth Ravages in Orchards Abated by Wasps.

Drs. J. E. Webb, Jr., and C. H. Alden of the Georgia State Department of Entomology, have presented some interesting data on how the wasp Trichogramma minutum has aided in abating the ravages of the codling moth and fruit moth in the Georgia peach and apple orchards. They state that during the past 10 years more than 300 million of these wasps have been raised and released to range the orchards. The wasp eggs are laid within the moth eggs and the wasp larvae then destroy the moth eggs. Upon collection and examination of moth eggs, it was found that more than 50 per cent had been rendered incapable of further development by the wasp larvae.

Bean Beetle Checked by Fly.

The Mexican bean beetle, now a serious crop pest in many eastern and southeastern states, will soon have a natural enemy to keep it in check in the United States just as it is checked in Central Mexico. Drs. B. J. Landis and N. F. Howard report that encouraging results have been obtained with a fly, Paradexodes epilachnae. These flies have been reared at Columbus, Ohio, for the past ten years and some 82,000 have recently been released in 19 states to aid in keeping the bean beetle in check.

Harmful Grubs Destroyed by Greenhead Ants.

Professor H. B. Fell of the University of Edinburgh has reported on studies he has made of a number of colonies of greenhead ants found in Australia. He states that the greenhead ant is of decided value to the farmer. He observed a single colony of a few hundred individuals over an eleven hour period and found them bringing in 125 larvae of beetles, moths and flies and a smaller number of various spiders, termites and red ants. Hence an estimated 45,000 harmful grubs would be destroyed by one colony of ants per year.

Physiological Researches.

Function of Corpora Allata in the Grasshopper.

Dr. I. W. Pfeiffer of Yale University has been carrying out physiological researches for the past ten years on the grasshopper, Melanoplus differentialis. She has recently reported another series of experiments on the function of corpora allata in these insects. These structures are somewhat similar in function to endocrine structures in higher forms known as corpora lutea. It was previously shown that the production of secretion by the oviducts and development of the eggs during the yolk deposition period was controlled by corpora allata, probably through a hormonal agency. Now it has been found by a series of transplantation experiments, that male corpora allata would perform the usual female function when grafted into females but when ovaries of the female were placed into males these ovaries would not develop yolk. This shows that while both males and females possess physiologically similar corpora allata the males no doubt also possess some inhibitory agent or a deficiency of some sort is present in the male which is vital to the egg during the yolk deposition period.

Insect Head Possible Additional Source of Internal Secretion.

Dr. M. F. Day of Harvard University has made a histological study of the heads of a number of species of insects and using the charactic staining reactions, on a number of structures in the heads of these insects, he suggests additional possible sources of internal secretions from the heads of some holometabolous insects.

Wound Healing in Grasshopper.

Mr. Garth Johnson of the State University of Iowa has reported a detailed description of the process of wound healing in the grasshopper. In general the process is more or less similar to that found in vertebrates except the scar tissue in these forms seems to develop from differentiated blood cells which is then followed by an activation of adjacent epidermis.

Life Tables of the Flour Beetle.

Dr. R. Pearl of Johns Hopkins University and Drs. T. Park and J. R. Miner of Chicago and the Mayo Clinic have recently reported life tables for the flour beetle Tribolium confusum Dutal while working on their experimental studies on the duration of life. Life tables were constructed for 400 male and 400 female beetles. The mean duration for males was 177.8 and for females 198.5 days. One male had a maximum life span of 540 days and one female 435 days. The interesting thing about these life tables was their close resemblance in fundamental pattern to human life curves. In fact the resemblance is closer than that of any other organism for which life tables have as yet been computed.

Cytological Experiments.

On Male Reproductive Cells in Grasshoppers.

Drs. H. W. Beams and R. L. King of the State University of Iowa have carried out some interesting cytological experiments on the male reproductive cells in the grasshopper. Mitotic spindles in the metaphase stage were partially or completely separated from the chromosomes by ultracentrifuging. Aside from the details of the experiment the important point was the additional evidence that the mitotic spindle is a body of substantial nature and was not destroyed (liquefied) by ultracentrifuging.

Cell Number and Cell Size in the Growth of Insects.

Interesting observations on the cell number and cell size in the growth of insects have been carried out by B. N. Smallman of McGill University. In general, it was found that tissues which were destined to be histolyzed during metamorphosis tended to grow by increase in size of their cells while tissues which persist to the adult stage tended to grow by an increase in cell number.

Enzymes in Insects.

Work from a number of institutions has been continued on researches concerned with the physiological and histochemical investigation of enzymes in an attempt to more precisely find the origin or source and also the action of these enzymes in insects. Most of the work along these lines has been carried out to date on the dragonfly and the grasshopper. See also BIOLOGY; ZOOLOGY.