139 



interesting case of disease due to direct attack is tick paralysis. The 

 a,ttachment of the tick causes progressive paralysis, until all parts of 

 the body are involved. Experiments have shown that the disease is 

 not infectious. Investigation of beriberi has thrown much hght on 

 effects of various toxins on the system. Observations on the larvae 

 of Gastrophilus sp. seem to show that the presence of insects in large 

 numbers in food may result in the formation of toxins, or may produce 

 the destruction or "^ reduction of the so-called vitamines. Among 

 l)acterial pathogenic organisms transmitted by insects are those 

 causing anthrax, bubonic plague and typhoid. In the case of protozoan 

 parasites causing malaria, sleeping sickness, nagana, etc., the insect 

 acts as an intermediate host. Among Nematodes, species of Filaria 

 are transmitted by insects ; there is probably a connection between 

 a Nematode carried by cockroaches and carcinomatous lesions in the 

 internal organs of mice. The disease of dogs caused by the Cestode, 

 Diphhjdium caninum., is transmitted by fleas. Mites, ticks, Diptera, 

 Hemiptera, Siphonaptera, and occasionally Lepidoptera and Coleoptera 

 may be concerned in disease transmission. Various relations exist 

 between disease organisms and the insect host, among them being the 

 mechanical and special or obligatory relations. Methods of infection 

 are the sucking of blood and its regurgitation, the contamination of 

 food, and possibly the secretion of specific toxins. Although the 

 majority of insect-borne diseases are endemic in tropical and sub- 

 tropical regions, exceptions occur in typhus fever, spotted fever of 

 the northern part of the United States, tuberculosis and pneumonia. 

 The study of the diseases is at present hampered by a lack of knowledge 

 of the insects involved. For example, very httle is known of the 

 PsYCHODiDAE, which may transmit pappataci fever. The vital 

 importance of entomological knowledge has recently been shown in 

 the case of an equine disease caused by Trypanosoma hippicum, 

 IseUeved to be transmitted by ants. 



Kramer (S.D.). The Effect of Temperature on the Life Cycle of Mmca 

 domestica and Culex pipiens.— Science, Philadelphia, xli, no. 1067, 

 nth June 1915, pp. 874-877, 2 tables. 



In the series of experiments carried out by the author, an effort 

 was made to eliminate all factors except that of temperature. 

 Individual variations among different batches of eggs were eliminated 

 by dividing the same batch into three parts to be incubated at the 

 thi-ee temperatures. Larvae reared from the batches of eggs compared, 

 were fed on the same food. The light was diffused or absent. By 

 exposing several tumblers of water in each incubator, the atmosphere 

 was kept in a high state of saturation. Incubation was carried out at 

 temperatures of 20°, 30° and 35° C. for M. domeMica and at 20° C, 

 room temperature, and 30° C. for Ctdex. Eecords were made of the 

 •date of appearance of larvae, pupae and adults. In the case of 

 M. domestica, results showed that a rise of 10° (from 20° to 30° C.) 

 practically halved the period between the egg and adult stages, while 

 a further rise of 5° shortened it still further by about two days. 

 .Similar results were obtained in the experiments with C. pipiens. 



