_Phryganids_ ‘live in the imago stage for at least a week and probably longer, apparently without taking food’ (letter from Dr. Hagen). According to the latest researches _Phrygane grandis_[10] never contains food in its alimentary canal, but only air, although it contains the latter in such quantities that the anterior end of the chylific ventricle is dilated by it. III. Strepsiptera. The larva requires for its development a rather shorter time than that which is necessary for the grub of the bee into the body of which it has bored. The pupa stage lasts eight to ten days. The male, which flies about in a most impetuous manner, lives only two to three hours, while the female lives for some days. Possibly the pairing does not take place until the female is two to three days old. The viviparous female seems to produce young only once in a lifetime, and then dies: it is at present uncertain whether she also produces young parthenogenetically (cf. Siebold, ‘Ueber Paedogenesis der Strepsipteren,’ Zeitschr. f. Wissensch. Zool., Band. XX, 1870). IV. Hemiptera. _Aphis._ Bonnet (‘Observations sur les Pucerons,’ Paris, 1745) had a parthenogenetic female of _Aphis euonymi_ in his possession for thirty-one days, from its birth, during which time it brought forth ninety-five larvae. Gleichen kept a parthenogenetic female of _Aphis mali_ fifteen to twenty-three days. _Aphis foliorum ulmi._ The mother of a colony which leaves the egg in May is 2‴ long at the end of July: it therefore lives for at least two and a half months (De Geer, ‘Abhandlungen zur Geschichte der Insekten,’ 1783, III. p. 53). _Phylloxera vastatrix._ The males are merely ephemeral sexual organisms, they have no proboscis and no alimentary canal, and die immediately after fertilizing the female. _Pemphigus terebinthi._ The male as well as the female sexual individuals are wingless and without a proboscis; they cannot take food and consequently live but a short time,—far shorter than the parthenogenetic females of the same species (Derbès, ‘Note sur les aphides du pistachier térébinthe,’ Ann. des sci. nat., Tom. XVII, 1872). _Cicada._ In spite of the numerous and laborious descriptions of the Cicadas which have appeared during the last two centuries, I can only find precise statements as to the duration of life in the mature insect in a single species. P. Kalm, writing upon the North American _Cicada septemdecim_, which sometimes appears in countless numbers, states that ‘six weeks after (such a swarm had been first seen) they had all disappeared.’ Hildreth puts the life of the female at from twenty to twenty-five days. This agrees with the fact that the Cicada lays many hundred eggs (Hildreth states a thousand); sixteen to twenty at a time being inserted into a hole which is bored in wood, so that the female takes some time to lay her eggs (Oken, ‘Naturgeschichte,’ 2^{ter} Bd. 3^{te} Abth. p. 1588 et seq.).