RELATIONS OF ANTS TO OTHER INSECTS. 345 



repeating the blunders of Linne and his successors. The actual condi- 

 tions are shown in the figure (Fig. 204) which, for lack of a better one, 

 I reproduce from the recent papers of Mordwilko (1896, 1907). 



What, then, is the function of the siphons? The early writers 

 replied to this question with a variety of more or less fantastic suppo- 

 sitions, although in general they believed these organs to have a secre- 

 tory function. Reaumur was the first to remark that the siphons 

 secrete a liquid of a more yellowish color than that expelled from the 

 anus, and subsequent authors have shown that the siphonal secretion 

 has a sticky and wax-like consistency. Biisgen finally pointed out the 

 usefulness of this liquid. " I was able," he says, " to ascertain the 

 function of the tubules by observing the operations of a lace- wing larva 

 [Chrysopa], the so-called aphis-lion, among a drove of plant-lice. This 

 pale yellow animal, with a dark dorsal stripe and a length of only a 

 few millimeters, hatches from a small egg, which is found during the 

 summer attached by means of a long stalk to the most various plants. 

 The larvae are usually found on the lower surface of the leaves, and 

 are easily captured, notwithstanding their agility. Their food consists 

 in great part of plant-lice which they seize with their sucking mandibles 

 and hold fast till reduced to mere shrivelled bits of chitin. When 

 these larva? are to be used for experiment, they are best left to starve 

 for a night and then placed among a drove of aphids suitable for 

 observation. When attacking they strike their jaws from below into 

 the body of the plant-louse with a sudden blow and at once begin to 

 suck out its juices. When the attack happens to be rather awkward, 

 the aphid has time to smear the secretion, which is at once discharged 

 from the tubules, over the face and forceps of the larva, which is thus, 

 at least temporarily, disconcerted and frightened. To be sure, I never 

 saw a larva free an aphid which it had once succeeded in seizing. The 

 .secretion hardens on the larva immediately and thus forms a most 

 uncomfortable coating, causing the creature to desist from the chase, 

 while it cleanses its forceps and forehead. This consumes time and 

 can only be accomplished by the aphis-lion's seizing some slender object, 

 like the tooth of a leaf, for the purpose of rubbing off the secretion. 

 While in such a helpless condition, it may itself fall a prey to enemies 

 which it need not fear at other times. Its agility and sucking jaws,. 

 capable of being opened to an extraordinary width, make it a formid- 

 able enemy even to the ants, which it may actually overcome in the 

 dark. On two occasions after confining a brown garden ant [Lasius 

 niger], the most frequent guest of our aphid droves, in a small box 

 with an aphis-lion, I found the ant sucked dry in the course of a few 

 hours. In the day-time, however, I have seen the ants drive the larvae 



