370 



TEXT-BOOK OF ENTOMOLOGY 



distance of 5 and even 10 cm. (4 inches) a yellowish-brown liquid or 

 emulsion with the odor of a mixture of carbolic acid and creosote. 



The large eversible dorsal glands of the Blattidse, since they con- 

 tain numerous hairs, which, when everted, are fan-like or like tufts, 

 serve, as in the spraying or scent apparatus, to disseminate the odor, 

 and might be classified with the alluring unicellular scent-glands or 

 dnftapparat of other insects, as they are by some authors ; but as the 

 glands are large and compound they may prove to be the homologues 

 of the coxal glands rather than of the dermal glands. 



Evaginable organs in the Blattids were first observed by Gerstsecker 

 in both sexes of Corydia; they are yellowish white, covered with 

 hairs, and are thrust out from between the dorsal and ventral plates 

 of the 1st and 2d abdominal segments. 



In the cockroach (P. orientalis) Minchin detected two pouch-like 

 invaginations of the cuticle, lying close on each side of the middle 



FIG. 359. Under side of end of Aphlebia, showing 1 the two eversible sacs ; p-^Y, five last abdomi- 

 nal segments; A, portion showing the hairs; B, showing origin of a hair in its follicle. After 

 Krauss. 



line of the body between the 5th and 6th tergites of the abdomen. 

 They are lined by a continuation of the cuticle, which forms, within 

 the pouches, numerous stiff, branched, finely pointed bristles, beneath 

 which are a number of glandular epithelial cells. In the male nymph 

 of P. decorata he also found beside these glandular pouches " an ad- 

 ditional gland, opening by a tubular duct under the intersegmental 

 membrane between the 5th and 6th terga above the glandular pouch 

 of each side, and extending forward into the body cavity. The gland 

 and its duct are proliferations of the hypodermis, and there is no in- 

 vagination of the cuticle." These eversible glands are most compli- 

 cated in Phyllodromia germani<-<i. While it is absent in the female, 

 in the male it is relatively of enormous size, extending over the 6th 

 and 7th somites, as well as projecting far into the body cavity (Min- 



