68 Zoologica: N. Y. Zoological Society [HI; 3 



they are at once immobilized or impeded in their movements 

 when they happen to run or fall into a minute drop of water, and 

 if the Ps. hromelise were at all hostile to the beetles or their 

 larvae in the manner described by sulc, their presence would 

 not only be a nuisance but a serious menace to the colonies. The 

 further fact that the coccids in a petiole are frequently decimated 

 or even exterminated by several small predatory insects {vide 

 infra p. 78) is also unfavorable to sulc's contention. 



I am, of course, willing to admit that the ostioles may be 

 glands or exudate organs which secrete substances that may be 

 ingested by the beetles and their larvae, but the closest observa- 

 tion of which I was capable showed that the only liquid visibly 

 imbibed by the Coccidotrophits was the saccharine excrement, or 

 honey-dew. If the secretion of the ostioles is a liquid, it must 

 be emitted in droplets too minute to be visible under a Zeiss lens 

 magnifying 20 diameters, or it must be a volatile substance like 

 that secreted by the peculiar tubular organs which occur on 

 the eighth abdominal segment of many ant-attended Lycaenid 

 caterpillars and have been described by de Niceville (1890). 

 Thomann (1901) and others.^ That the ostioles of P.s. hrovielise 

 may actually emit some substance attractive to the beetles and 

 their larvse is indicated by their often very prolonged stroking 

 of the dorsal, lateral or anterior portion of a coccid. That they 

 prefer to stroke its terminal abdominal segments may be due 

 to the fact that that region bears both the anus and the poster- 

 ior pair of ostioles. 



The attraction of the mealy-bugs, whether due solely to their 

 ability to excrete honey-dew or because they can also secrete some 

 delicious exudate or fascinating aroma, is so great, that in popu- 

 lous colonies a single coccid may often become the center of a 

 circle of actively competing beetles and larvae of various sizes. 

 This is not so apparent in colonies that have just been collected 

 and placed in glass tubes, because the petiole still contains a cer- 

 tain amount of sap and the coccids are able to excrete normally, 

 but after the colonies have been kept for several days or a 



' Conf. also the paper of Newcomer (1912), who figures a section of one 

 of these oi'gans in Lycaena piasus (PI. 2, Fig. 3). Although he believes 

 that the tubular organs are not glandular, the structural details certainly 

 seem to support Thomann's contention. 



