Organs of Secretion. ^^^^ 57 



lice, the excrement, as well as the fluid that escapes in some 

 species from special tubes called the nectaries, is very sweet, 

 and in absence of floral nectar will often be appropriated by 

 bees and conveyed to the hives. In those insects that suck 

 their food, as bees, butterflies, moths, two-wing flies and bugs, 

 the feces are liquid, whUe in case of solid food the excrement 

 is nearly solid. 



SECEETORY ORGANS OF INSECTS. 



I have already spoken of the salivary glands, which Kirby 

 gives as distinct from the true silk-secreting tubes, though 

 Newport gives them as one and the same. In many insects 

 these seem absent. I have also spoken of the mucous glands, 

 the urinary tubules, etc. Besides these, there are other secre- 

 tions which serve for purposes of defense. In the queen and 

 workers of bees, and in ants and wasps, the poison intruded 

 with the sting is an example. This is secreted by glands at 

 the posterior of the abdomen, stored in sacks (Fig. 28, e), and 

 extruded through the sting, as occasion requires. I know of 

 no insects that poison whUe they bite, except it be mosquitoes, 

 gnats, etc. , and in these cases no special secreting organ has 

 been discovered. Perhaps the beak itself secretes an irrita- 

 ting substance. A few exceedingly beautiful caterpillars are 

 covered with branching spines, which sting about like a nettle. 

 We have two such species. They are green, and of rare at- 

 traction, so that to capture them is worth the slight incon- 

 venience arising irom their irritating punctures. Some in- 

 sects, like bugs, secrete a disgusting fluid or gas which afibrds 

 protection, as by its stench it renders these filthy bugs so offen- 

 sive that even a hungry bird or half-famished insect passes 

 them by on the other side. Some insects secrete a gas which 

 is stored in a sack at the posterior end of the body, and shot 

 forth with an explosion in case danger threatens; thus by 

 noise and smoke it startles its enemy, which beats a retreat. I 

 have heard the little bombardier beetle at such times, even at 

 considerable distances. The frightful reports about the ter- 

 rible horn of the tomato-worm larva are mere nonsense; a 

 more harmless animal does not exist. My little boy of four 

 years, and girl of only two, used to bring them to me last sum- 

 mer, and regard them as admiringly as would their father up- 

 on receiving them from the delighted children. 



