I2l8 INJURIOUS INSECTS AND OTHER LOWER ANIMALS 



These investigations, which are not yet terminated, appear however to 

 have shown that this figure is too low. It is quite possible for a female to 

 lay up to 100 eggs. 



Development of the genital organs — The investigations carried out 

 show that the larvae of Lyda ready for pupation already possess well de- 

 veloped sexual organs while in other insects, e. o. the lepidoptera, the 

 ovaries are still little developed even in the last larval stage. The gen- 

 ital organs form during the summer and autumn, at the same time as the 

 " pupal eyes ", but the Author does not think that there is any relation be- 

 tween the formation of these two organs. The testicles develop more rapidly 

 than the ovaries. A very detailed description is given of the genital organs 

 and the formation of the eggs. 



The freshly emerged female, after mating, lays in the first oviposition 

 about 30 eggs ; later on, when the weather is hot, it lays more. Oviposi- 

 tion is complete at the end of 7 days. If it is rapid and intense the adult 

 dies after 8 days of life. The arrival at maturity and oviposition are closeh' 

 related to the weather ; hot weather promoted them, bad weather hinders 

 them. If bad weather is sufficiently prolonged the females die before ovi- 

 positing, and the consequence frequently is a rapid diminuton of the insects 

 in the forest. 



Colour of the larvae. — Generally green larvae and yellow larvae are 

 distinguished, but there are also all kinds of shades between these two groups. 

 Among the larvae studied in 1913, 88 % were green and 12 °o ^^ellow. The 

 hypothesis that the green larva is male and the yellow female was not 

 confirmed by the present investigations. The colour is not changed until 

 the larva has pupated. 



It is likewise not true that the yellow larvae are individuals covered 

 with parasites. The difference in the colour results from the blood of the 

 larvae. 



Parasites. — L. hypotrophica appears to suffer little from parasites ; 

 no parasites are known to attack the eggs, pupae or adults. On the other 

 hand the larva is attacked by some species of Ichneumonidae and Diptera, 

 but not to a great degree. 



The larva of Ichneumonidae found b}^ the writer in the larva of Lyda 

 in October and spring, were still very small : 3-4 mm. Later, in the month 

 of March, they were 6 mm. On being placed in a hot room they developed 

 more rapidty, and produced adults within a few weeks. 



The larvae of Ichneumonidae completely absorb the larvae of Lyda so 

 that after a time nothing remains but the empt}' skin. They afterwards 

 leave their hosts in order to pupate. 



The Tachinid larvae living in the larvae of Lyda are more developed 

 than the Ichneumonid larvae. They were already' completely developed in 

 October and entirely filled out the Lyda larvae. 



They would remain therein during the winter and would only pupate 

 in the following spring, when the weather is warmer. Thus these pa- 

 rasites are only found in small number in the larvae of Lyda 



The larvae of Ichneumonidae and Tachinidae are only found in those 



