EFFECTS ON THE HIGHER INVERTEBRATES 27 



The Orthoptera (grasshoppers) and Lepidoptera (butterflies and moths) endure 

 starvation generally only a few days. The time varies inversely with the 

 temperature and (in general) directly with the age; but in some cases (certain 

 flies and beetles) the normal larval period may be prolonged by underfeeding. 

 In the grasshoppers, the period of endurance is doubled if water is allowed. 

 In all species there are also great individual variations. 



Effects on Body Weight and Size. — As pointed out by Putter ('n) the possi- 

 ble decrease in dimensions during inanition is much less in those forms having 

 a firm skeleton (e.g. Arthropoda). The maximum possible reduction in body 

 weight and size varies greatly among the higher invertebrates, ranging from 15 

 or 20 per cent in some Arthropoda to over 90 per cent in some coelenterates and 

 planarians. Among coelenterates, Hydra is reduced to ^7 or less in length; 

 the jellyfish Amelia to ^ and Cassiopea to ^5 of the original volume. Plan- 

 arians (flatworms) may be reduced to ^{2 m length and to 3^300 i n volume. In 

 the snail Helix, the loss in weight apparently varies from n to 50 per cent or 

 more, according to species and conditions, with much individual variation. 

 Among the Arthropods, a loss of 75 per cent in weight is recorded for the water- 

 flea Daphnia, and of 15 per cent for the crayfish Astacus. Great variation has 

 been found among the insects. 



There are relatively few data on the loss during inanition in larval stages. 

 The larvae of the sea-urchin Strongylocentrotus Hindus may decrease to half the 

 diameter of the original ovum. Chortophaga nymphs lose 20-25 per cent, and 

 the tent-caterpillar (Clisiacampa) 35 per cent. The remarkable reduction (to 

 3^o 0) m the larva of the beetle Trogoderma is apparently exceptional. The loss 

 during the pupal stage in general appears relatively slight. 



Hall ('22) found marked differences in the limits of exsiccation in various 

 invertebrates and vertebrates (see table on p. 116). 



Effects on the Form of the Body. — During inanition the body is not only 

 reduced in size, but also frequently more or less changed in form. Hydra for 

 example, becomes at first abnormally elongated, later greatly contracted and 

 relatively broader. The water-flea Daphnia presents a peculiar modification 

 of body form attributed to malnutrition, and said to be hereditary (Woltereck). 

 In the sponges, the coelenterates (Hydra and Cassiopea) and the planarians the 

 changes are remarkably great, not only in external form, but also in correspond- 

 ing internal structure. The so-called "reduction" process in these forms more 

 or less resembles a reversal of the developmental process, which will be discussed 

 later. In planarians, the involution frequently involves the posterior portion 

 of the body to a greater extent, resulting in a relative enlargement of the head 

 region. This is also true of the nemertin worm Lineus lacteus, but not of 

 Lineus ruber, which illustrates the differences which may occur between species. 



Changes in Various Organs and Tissues. — It is a remarkable fact that the 

 various organs and tissues of the body differ very greatly in their resistance to 

 inanition. Some undergo changes very quickly, others only after longer periods, 

 and still others show a remarkable resistance. There are also differences in the 

 extent of atrophy, as well as the order of sequence. The gonads will be dis- 

 cussed separately later, and also the changes in the developing organism. 



