EFFECTS ON THE HIGHER INVERTEBRATES 6 1 



to endure starvation is one factor explaining the long periods in which deserted 

 houses and camps may remain infected. 



Among the plant-lice (Aphidiidae), as in the case of the rotifers and daphnids, 

 the effects of inanition have been studied chiefly in their relation to sexual repro- 

 duction. Kyber (1813) noted that male forms result from underfeeding, a 

 result apparently confirmed by Leydig and others. Goldi ('85) found that with- 

 drawal of food results in the appearance of the winged forms in Pemphigus 

 xylostei, Pemphigus bumeliae and Lachnus. Thus even in June the winged 

 forms of Schizoneura lanigera are obtainable, leading directly to the sexual 

 generation. Keller ('87) and Behr ('92) observed that also in the grape-louse, 

 Phylloxera vastatrix, deficiency of food causes cessation of parthenogenesis and 

 the appearance of the sexual, winged forms, containing males as well as females. 

 According to Keller ('87), this confirms the theory of Landois and Dusing as 

 to the relation of nutrition to sex, the males appearing only under unfavorable 

 conditions. 



Diptera. — Cuenot ('99) found that in the maggots of flies the sex-ratio is 

 not materially affected by the quality or quantity of food. Tangl ('09) 

 found that in fasting larvae of Ophyra cadaverium, the metabolism is chiefly 

 at the expense of the fat. Starvation of the larvae retards the process of 

 metamorphosis. In connection with a study of the chromidia, Popoff ('10) 

 noted changes in the fat cells, "oenocytes" and pericardial cells of the housefly 

 during feeding and inanition. Guyenot ('13, '13a, '13b, '13c) made a series of 

 studies upon the relations of nutrition and reproduction in the fruitfly, Droso- 

 phila ampelophila. If the larvae are reared on sterilized potato, instead of 

 yeast, they undergo metamorphosis but with atrophic gonads, sexual maturity 

 being markedly retarded. The eggs laid by such abnormal forms are few in 

 number and give rise to weak and short-lived larvae. In the second article 

 ('13a), it was shown that the fecundity depends upon the environment, not 

 only of the larvae, but also of the pupae and the adult fly. Drosophila is thus 

 intermediate between these insects (certain butterflies) whose sexual maturity 

 is determined entirely by larval nutrition, and those (Calliphora) where the 

 sexual maturity is not so affected and depends almost entirely upon adult nutri- 

 tion. Later ('13b) it was shown that when adult females are placed on poor 

 nutriment (potato or carrots) the eggs become abnormal and greatly reduced in 

 number. " Apres avoir pondus quelques oeufs, donnant des larves, les femelles 

 pondent quelques oeufs dans lesquels se forme un embryon, generalement 

 anormal, qui meurt a un stade plus ou moins avance." Later the malnourished 

 females lay unfertilized ova, even when conjugation with the male occurs, the 

 spermatozoa apparently being resorbed in the seminal receptacle of the female. 

 Finally, Guyenot ('13c) demonstrated that the process of egg deposition is, 

 in part, determined by the nutritional conditions. 



Further studies on the nutritional relations of the fruitfly (banana-fly) 

 Drosophila were made by J. Loeb ('15, '15a) who grew five successive generations 

 on a solution of glucose, cane sugar, ammonium tartrate, citric acid, dipotas- 

 sium phosphate and magnesium sulphate. Bacteria and yeast were not 

 excluded, however. Loeb and Northrop ('16), by special precautions, reared 



