FREE AMINO ACIDS IN INSECTS 125 
presence of methionine sulfoxide, taurine and ethanolaminophosphoric acid in the 
silkworm egg has been reported (NARUMI ef al.4°; SASAKI et al.'®). 
SHAw!63 detected in the egg of the grasshopper Chortophaga viridifascrata, in addition 
to other amino acids, methionine sulfoxide, citrulline and ethanolaminophosphoric 
acid. The author considered that methionine sulfoxide was an oxidation product of 
methionine formed during the preparation of extracts. Ethanolaminophosphoric acid 
is probably related to the intermediary metabolism of serine and glycine. Other amino 
acids of general occurrence such as aminobutyric acid, cystine, taurine and hydroxy- 
proline were not found. There is no qualitative difference of the amino compounds in 
eggs of different ages, but the concentration appears in general higher in later develop- 
ment. 
A detailed study on the S-containing amino acids in developing eggs of the grass- 
hopper Melanoplus differentialis has been carried out by Fu. The total content of 
sulfur remained unchanged during embryogenesis. In pre- and post-diapause, me- 
thionine and cystine-cysteine showed distinct fluctuations, which obviously reflect 
metabolic changes between these amino acids and between yolk and embryonic 
proteins. However, during the period of diapause the values remained strikingly con- 
stant. In the late post-diapause a definite drop in the contents of these amino acids was 
observed, indicating their degradation or destruction through oxidation, and their 
conversion into —SH or —S-S-containing compounds like coenzymes. The relation 
between growth and changes in free -SH groups in the grasshopper embryo has been 
analyzed by NorMAn™®, 
In the Moroccan locust Dociostaurus maroccanus, LICHTENSTEIN et al.!4 demonstrated 
that glycerine extracts from eggs at diapause were active in hydrolyzing peptone, 
leucylglycine, leucylglycylglycine, and chloroacetyltyrosine, but neither casein nor 
gelatine were attacked by such extracts. However, using extracts from eggs in active 
development and shortly before hatching, digestion of casein was observed. There is 
thus a distinct difference in the proteolytic enzyme system between eggs at diapause 
and those at post-diapause. 
Larval and pupal development 
Growth is no doubt the dominant phenomenon during larval development, while 
histolysis and histogenesis are the main changes at metamorphosis. The large fluctua- 
tions of free amino acids during these developmental periods are apparently related 
to the morphogenetic processes. In general, the larvae have comparatively higher 
amino acid concentrations than the pupae or adults. Metabolic changes in free 
amino acids during post-embryonic development have been reported for Drosophila 
melanogaster (HADORN AND MITCHELL®; CHEN AND HADORN*®; CHEN%®; BENz?9), 
Culex pipiens (CHEN®®), Culex quinquefasciatus and Aedes aegypti (MICKS AND ELtts!¥°), 
Calliphora augur (HAcKMAN®*), Calliphora erythrocephala and Phalera bucephala 
(AGRELL!), Ephestia kiihniella (CHEN AND Ktun"; Bombyx mort (SARLET et al,.1®9, 191; 
AMANIEU et al.3), Galleria mellonella (AUCLAIR ET DUBREUIL®), Saturnia pyri (STAMM 
AND AGulIssE!”!), Macrothylacea rubi (DRILHON*!) and Tenebrio molitor (PATTERSON™?). 
In D. melanogaster the total amount of free ninhydrin-positive substances for 
larvae increases rapidly up to 72 h after egg-laying, remains more or less constant for 
the next 24 h, and then drops steadily at the time of pupation (HADORN AND STUMM- 
References p. 132/135 
