﻿112 Journal New York Ent. Soc. [Voi. hi. 



acting specially to retract the gland. The creature can squirt to a dis- 

 tance of five and even ten centimeters (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 Blattidae, since they contain 

 numerous hairs, which, when everted, are fan-like or like tufts, serve, as in 

 the spraying or scent apparatus, to disseminate the odor, might be classi- 

 fied with the alluring unicellular scent glands or duftapparat 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 Gerst?ecker 

 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 

 first and second abdominal segments. 



In the cockroach {P. orientalist Minchin detected two pouch-like 

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

 of the body between the fifth and sixth 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 additional 

 gland, opening by a tubular duct under the intersegmental membrane 

 between the fifth and sixth 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 invagination 

 of the cuticle." These eversible glands are most complicated in Phyl- 

 lodromia gennanica. While it is absent in the female, in the male it is 

 relatively of enormous size, extending over the sixth and seventh somites, 

 as well as projecting far into the body cavity (Minchin). Haase states 

 that these glands become everted by blood-pressure and give out the 

 well-known disagreeable smell of these insects. He states that in the 

 male of P. germanica the dorsal glands in the sixth and seventh ab- 

 dominal segments are without hairs and produce an oily secretion ; 

 they function as odoriferous organs in sexual union. 



In the male of another Blattid {Aph/ebia bivitlata) of the Canary 

 Islands, Krauss has detected two yellowish dorsal sacs 1.5 mm. in 

 length, opening out on the seventh abdominal segment, and filled full of 

 long yellowish hairs, the ends directed towards the opening, where they 

 form a thick tuft. These eversible glands lined with hairs appear to be 



