Insecta. 259 



of two germ cells, a comparative study nf the variability of these structures 

 was inade. 



It was found tliat inside a given biotype — or inside a Single colony — 

 there is great variability in the number of these hooks. The study suggests that 

 the difference in average number of hooks in mid and late sunimer is due not 

 merely to differences of age, temperature and food conditions in these two 

 seasons, but probably also the biotype that forms inany hooks develops later in 

 the season. The advantage of this structure for further study is emphasized. 



Gates. 



Insecta. 



679) Swingle, L. D., The Life-History of the Sheep-Tick Melophagiis 



ovinus. In: Univ. of Wyoming Agr. Exp. Sta. Bul., Nr. 99, S. 1—24, 1913. 



The egg is fertilized and develoi)s through the embryonic and most of the 

 larval stage within the body of the female tick. It is laid as a larva which 

 changes into the pupa stage about 12 hours later. (For convenience the term 

 pupa is used to designate the offspring from the time it was born until it was 

 hatched). 



Pupae require during the summer months from 19 to 23 days to hatch. In 

 the winter from 19 to 36 days are required in case the sheep are kept in the 

 barn. Were they turned out of doors in the cold wind, the probability is that 

 in some cases the period niight increase to 40 or 45 days. The period of in- 

 cubation is greatly affected by the temperature, and therefore, by the distance 

 the pupae are laid from the skin of the sheep, especially in the winter. 



The time required for females to reach sexual maturity is variable. Gene- 

 rally it is from 14 to 30 days. Males and females are capable of copulating 

 within three or four days after hatching. The whole life of the tick is spent on 

 the sheep. They will not live more than a few days off their host. Female ticks 

 were followed for five and one-half months. Some probably live much longer. 

 Many die earlier. There is a great mortality among the young before they take 

 their first meal. 



The number of pupae laid by a female depends upon the length of her life. 

 For a female living four months the number is about 10 to 12 pupae. For one 

 living six months, the number is 15 or more. The rate of pupa laying, counting 

 from the time the first one is laid, is about oue pupa every 7 or 8 days. 



PearL 



080) Scymanski, J. S., Zur Analyse der sozialen Instinkte. In: Biolog. 

 Centralbh, Bd. 33, Heft 11, S. 649—658, 1913. 



Der Verf. fragt sich, wie die Erscheinungen des sozialen Zusammenlebens 

 und gemeinsamer Arbeiten bei Insekten zustande kommen. Lassen sie sich aus 

 der Eigenart der „primären" Reaktionen herleiten, welche jedem einzelnen Indi- 

 viduum der betreffenden Art als solchem zukommen, oder sind infolge des Zu- 

 sammenlebens diese primären Reaktionen zu „sekundären" abgewandelt worden, 

 derart daß sie nur bei gemeinsamer Lebensweise einen Sinn haben? 



Die Bildung des gemeinsamen Gespinstes der Raupen der Baumspindelmotte 

 {Hyponomeuta evonymella), ebenso wie das Entstehen der Freßgesellschaften bei 

 den Afterraupen von Arye (Hylotoma) ustulata L., ließen sich beide restlos auf 

 primäre Reaktionen zurückführen: Jedes Individuum reagiert, einzeln betrachtet, 

 genau so wie im Verbände mit den Artgenossen. — Nur eine Beobachtung 



17* 



