34 WILLIAM MORTON WHEELER. 



study, however, shows, unmistakable ethological similarities be- 

 tween the two families. Both are strongly heliophobic, or dark- 

 loving (negatively heliotactic) animals and hence *also positively 

 contact-loving or thigmotactic. Our wild cockroaches, like the 

 termites live in dead or decomposing wood or in the soil. Fur- 

 thermore, it can be shown that there are adumbrations of social 

 life among the Blattidae. Our domestic species are somewhat 

 gregarious in their adolescent and adult stages. Then, too, the 

 mother cockroach deposits her eggs in a peculiar ootheca which 

 she carries about in a kind of brood chamber formed by an in- 

 folding of the terminal segments of the abdomen. The ootheca 

 is, however, deposited before the young hatch. Entomological 

 treatises repeat the statement that the female " croton bug" 

 (Phyllodromia germanica) assists the young in escaping from the 

 ootheca. This observation is traceable to Hummel ('29) who 

 recorded it in a work which has become rather rare. The perti- 

 nent passage may, however, be found quoted in full in the works 

 of Audouin and Brulle ('35, pp. 36, 37) and Serville ('39, pp. 

 59, 60). The fact that in some of our species of Blattidae the 

 young can escape from the ootheca without maternal assistance, 

 casts doubt on these old observations. The female in these spe- 

 cies exhibits only the first rudiments of a social instinct in the 

 care of the young till they are nearly ready to hatch. 1 



A further extension of maternal care is seen in the beautiful 

 green South American cockroach, Panchlora viridis, which is 

 sometimes imported alive into stores and houses in New York 

 and Brooklyn. Riley, in three short papers ('90, '91 tf, '91^), 

 claimed that this insect is viviparous, but a moment's examination 

 of the very facts he has recorded, shows that it cannot even be 

 regarded as ovoviviparous. In his third paper ('91^) he figures 

 the semi-circular egg-mass of the insect with two rows of em- 

 bryos arranged with their ventral surfaces face to face, just as 

 others and myself have shown them to be arranged in the 

 ootheca of Phyllodromia and Periplaneta. Moreover, a delicate 



1 That the maternal instincts of the " croton bug " are highly variable is proved by 

 an observation communicated to me by Mr. Wm. Beutenmiiller while these pages are 

 going through the press. He found one of these insects surrounded by her young and 

 still retaining in her oothecal chamber the empty ootheca from which they had just 

 escaped. 



