270 Arthropoda. 



Ichneumons, pavthenogenetio reproduction has been observed ; for the most part, 

 males arise from the fertilised eggs. 



3. Sand-wasps {Crahronidse, Pompilidue). These, like the following 

 groups, have a simple trochanter, a stalked abdomen, and a sting. They are 



' active forms, and are chiefly characterised by their mode of Hfe ; they catch 

 Insects, and their larvae, or Spiders, paralyse them by a sting in the ventral neiTe 

 cord, and store them in buiTows, which they make in the earth or in wood ; they 

 lay one egg in each passage and then close it up ; the larva feeds vipon the stores 

 thus collected. Other forms divide the biuxows up into cells by means of clay 

 partitions, and deposit one egg in each cell ; others again form brandling tunnels, 

 and place one egg, with a supply of food, in each branch. More rarely they 

 bring fresh supplies of food to the larva daily. The allied G o 1 d - w a s p 

 (Chrysis), is a beautiful, metallic-looking insect, with a very hard chitinous 

 exoskeleton. This is especially firm on the abdomen, which is much arched above, 

 but concave below, and appears to be made up of a few large segments, the last 

 being telescoped. The antennae are geniculate. The body may be rolled up, so 

 as to present only the hard exoskeleton to the stings of the Sand-wasps, in 

 whose nests they lay their eggs. The larvae live as ecto-parasites upon the Sand- 

 wasp larvae. 



4. Ants (Formica/rise) are distinguished from other Hymenoptera in that 

 the second (or second and third) abdominal segment is considerably thinner 

 than the foUovrfng, and is provided with an upright scaley, or knob-like 

 outgi'owth ; the antennae are geniculate. Ants form colonies, consisting of 

 males, females, and workers ; the latter being females with imperfectly developed 

 sexual apparatus : both males and females have large wings, but those of the 

 latter are thrown off after copulation : the workers, on the other hand, are quit© 

 apteroiis. In some species two kinds of workers are nVet with, some with 

 large heads (soldiers), others with smaller heads (true workers). Some Ants (of 

 course only females and workers) possess stings, others have only the con-e- 

 sponding poison glands, the secretion fi'om which is squirted into the wound 

 made by the mandibles. The nests, which consist of iiTegular chambers and 

 labyi-inthine passages, are, in most cases, tunnelled in the earth, or gnawed out in 

 stumps of trees; the burrowing forms generally pile up the earth they dig 

 out above the nest, and thus form a hillock, into which the nest is continued ; 

 others (e.g., the Red-forest ant, Formica rufa), construct mounds of pine- 

 needles, leaves, and so on ; others again, build nests in hollow trees, constructing 

 the walls of sawdust, etc., cemented together with saliva. Ants are omnivorous ; 

 the lai-vae are fed by the workers upon comminuted food. The habits of these 

 insects are of the gi'eatest interest, and in many species the most remarkable 

 conditions may be obsei-ved. There are, for example (occmTing in England), 

 species which steal laiwse and pupae from the nests of others, and bring them to their 

 own ; the woi'kers, which develop from these, fonn a necessary contingent of the 

 working staff of the marauders, or may have to do all the work, even to feeding 

 their masters. In a Mexican species the abdomen of some workers is much 

 swollen in conseqvience of the enormous dilation of the crop, which is filled with 

 a honey -like fluid ; these workers remain in the nest whilst others are out seeking 

 for honey ; on their retuiTi the latter give their booty to the inactive fomis, which 

 thus serve as regular reservoirs for the honey supplies of the nest. Besides Ants, 

 an ant-hill harbours (just as in the case of the Termite nests) quite an insect 

 fauna on a small scale, the members of which are known as M y r m e c o p h i 1 o u s 

 Insects, e.g., several small Beetles, many of which are found here exclusively. 

 The relations between Ants and Aphides are well known, the Ants gi-eedily 

 sucking up the sweet excretion of the latter ; many ants even carry Aphides 

 into their nests, and keep them as " domestic animals." 



