IX 



COCKROACHES 



229 



This gland is niucli larger than the testes proper, which, it is 

 said, lose early their functional activity in the species in question, 

 and shrivel. There is another important accessory gland, the 

 conglobate gland of Miall and Denny, opening on a portion of 

 the external copulatory armour. 



Although some species of Blattidae are domesticated in our 

 houses, and their bodies have been dissected by a generation of 

 anatomists, very little is known as to their life histories. The 

 common " black beetle " of the kitchen is said by Cornelius to be 

 several years in attaining the adult state. Observations made at 

 Cambridge by the writer, as well as others now being carried on 

 there by Mr. H. H. Brindley, quite confirm this view, the extent of 

 growth accomplished in several months being surprisingly little, 

 and the amount of food consumed very small. It is therefore not 

 improbable that the life of an individual of this species may 

 extend to five years. Phyllodromia germanica, a species that is 

 abundant in the dwellings of the peoples of north-eastern Eiu:ope, 

 attains its full development in the course of a few months. 



We have already alluded to the fact that in the Blattidae the 

 eggs are laid in a capsule formed in the interior of the mother- 

 Insect. This capsule is a horny case varying much in size and 

 somewhat less in form in the different species ; it is borne about 

 for some time by the mother, who may not 

 infrequently be seen running about with it 

 protruding from the hinder part of the body. 

 Sooner or later the capsule is deposited in a 

 suitable situation, and the young cockroaches 

 emerge ; it is said that they are sometimes 

 liberated by the aid of the mother. Mr. 

 Brindley has found it very difficult to pro- 

 cure the hatching of the young from their 

 capsules. 



It is known that some Blattidae are 

 viviparous. In the case of one such species, 

 Fanclilora viridis, it appears probable that 

 the egg-capsule is either wanting, or is present in only a very 

 imperfect form.^ 



On emerging the young Blatta is in general form very similar 

 to the parent, though usually much paler in colour. After casting 

 1 Riley, Insect Life, iii. 1891, p. 443, and iv. 1891, p. 119. 



Fig. 126. Egg-capsules 

 of European Blat- 

 tidae. A, Ectdbia lap- 

 ponica ; B, Phyllo- 

 dromia gennanica ; 

 C, Heterogamia aegyp- 

 tiaca. (AfterBrunner.) 



