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Written by Mondy Ross
lllustroted by Kote ond Liz Pope
vook of oll these wi4onirnols!
NHich ones Qre big and heovy?
Ntrich ones Qlesno tp
5ortre wild animals runfost.
5orrre onimols live whereit,s hot.
\Aow monY honkeys con youspot? +f_
{hase
onimols live whereit,s co\d.
\Nf ttich on es have f ur to keep tharn worrn?
h\ tor the river ' /ots of anirnols corna
o splosh or o cool drink.
Con You snqP o crocodile's Yotrr hqnds ljke tTtouth?
\t{ ere off on c fuip fo spot wild on sols ' c\n You sh ow the jeepwhiCn
NoY to 90 to f ind the elephont s?
\tf hot do th ese onimals eat?
\tlould You like fo eatfhis kind
5orrre onirnols haveshorp teeth
.-d clows" ' or fusks , or beaks.
\Aow monY teeft have you got?
5or$e onimols havepqfi erns to 6a\P tharn hide a or forsh owingoffl $,r
you rnotch the anirnols to r Potterns? "- ", con \hai ri i
ru,t, ll l,lo ,t,l ,'. 'Yt t l', tl ' '-1 "! >. 'l a, r,l '/
'l ? ro .a '"!!,';1i';';\',"1 !" lr or lo t , t -* -*F' | ,j', l. 'l ."" .:.-, ilr is, 3 a)o \f l|r r I t l\f
Con You moke these animol no ise,i?
r:a-J r r-39t.r
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adult Hymenopterous Insect it would appear that the first abdominal ganglion is always joined with the last thoracic.
Sub-Orders.—The distinction in the form of the abdominal articulation, previously alluded to (p. 492, Fig. 336, A, B), divides the Hymenoptera into two great sub-Orders, the members of which are very different in their habits and life-histories. The Sessiliventres are plant-eaters; their larvae (Fig. 343, A) are provided with legs, and are able to procure their vegetable food for themselves. The larvae of the Petiolata are maggot-like and helpless, and are dependent for food on supplies afforded them by their parents or companions. It is said by Dewitz that although the larvae of the Petiolata appear to be legless, there are thoracic legs within the body. The metamorphosis, so far as it is known, and the early life-history of the Sessiliventres are very similar to those of butterflies and moths, except that the pupa is soft and has no hard external skin. A few of these planteating Sessiliventres become carnivorous in the perfect state—a change of habit that is most unusual in Insects, though the reverse occurrence is common. The larvae of the Petiolata exhibit, in the cases that have been examined, the peculiarity that the alimentary canal has not any outlet posteriorly until the termination of the larval stage of existence is approaching. In some cases there is no anal orifice; in others this orifice exists, but there is no communication between the stomach and the posterior intestine.
Packard informs us[415] that in Bombus the larva, after it is full fed, passes into the pupa state (Fig. 331, A, B) by a series of transformations accompanied by moultings of the skin. Packard's statements have been confirmed by others, but details have not been fully given, so that the number of the moults, their intervals and other particulars, are still unknown. We have remarked that the pupal instar is very like the perfect instar, except that it is colourless and soft, and that each of the members is wrapped in a very delicate skin; the colour appears gradually. This metamorphosis exhibits important differences from that of the Lepidoptera. Packard calls the Insect, during the stages of transformation from the full-fed larva to
the pupa, the semi-pupa; the later stages of the pupa, when the colouring has appeared, he terms the subimago. Altogether he considers there is a series of at least ten moultings of the skin. His ideas were apparently derived from examination of a series of specimens after death rather than from observation of the development in living individuals. The parasitic forms of Hymenoptera have apparently extraordinary metamorphoses of very varied kinds.
Parthenogenesis.—One of the most remarkable facts connected with this Order is the prevalence of parthenogenesis in a considerable number of widely separated species. In many of these Hymenoptera it is not a mere occasional occurrence, but plays an important part in the continuity of the species; indeed, it is believed that in some members of the Order the reproduction is entirely parthenogenetic. We shall give particulars as to some of these cases in subsequent chapters, and will here make some remarks on the different forms of parthenogenesis existing in the Order. The three forms of parthenogenesis mentioned on p. 141 all occur in Hymenoptera. In the gall-making Cynipidae parthenogenesis is frequently accompanied with alternation of generations, a generation consisting of the two sexes being followed by another consisting entirely of females, which in its turn gives origin to a bisexual generation. In this case deuterotokous parthenogenesis is established as a part of the normal economy of the species. This same form of parthenogenesis also occurs in other species of Cynipidae unaccompanied by alternation of generations. Thus in Rhodites rosae the generations resemble one another, and the male is very rare, but is still occasionally produced,[416] and the same condition exists in other Cynipidae. According to the observations of Adler, we may assume that the male, in the latter cases, is useless, the continuation of the species being effected by virgin females although males exist. Deuterotokous parthenogenesis also occurs in the sawflies, but as a comparatively rare phenomenon.[417]
Thelyotokous parthenogenesis is common in sawflies, and it also occurs in some Cynipidae. There are several species of this latter family in which no males have ever been found.[418] The phenomena in Rhodites rosae we have mentioned, give rise to the idea that in that species deuterotokous parthenogenesis occurs as an exception, the species being usually thelyotokous. A most remarkable case of thelyotokous parthenogenesis is said to exist in the case of the parasitic ant Tomognathus. This species is said to be monomorphic, only the female existing, and reproducing by uninterrupted parthenogenesis.
Arrhenotokous parthenogenesis—i.e. parthenogenesis in which the progeny is entirely of the male sex—occurs in several species of sawflies. We find it also occurring in the case of the social Hymenoptera; the workers of ants, bees, and wasps occasionally produce eggs parthenogenetically, and the progeny in these cases is always of the male sex. In the honey-bee the queen sometimes produces eggs before she has been fertilised, and the parthenogenetic young are then always of the male sex.
Some species of Hymenoptera exhibit two forms of parthenogenesis. In Nematus curtispina the parthenogenetic generation is generally of the male sex, but a female is occasionally produced;[419] while in Hemichroa rufa parthenogenesis may result in either deuterotokous or thelyotokous progeny. No case is yet known of a species exhibiting the three forms of parthenogenesis. From this review we may conclude that parthenogenesis does not favour the formation of one sex more than another; but it is clear that it decidedly favours the production of a brood that is entirely of one sex, but which sex that is differs according to other circumstances.
Production of Sex.—It is believed that a very peculiar form of parthenogenesis exists in the honey-bee, and it is confidently stated that the drones, or males, of that species are always produced from unfertilised eggs. These views are commonly called the Dzierzon theory, and are widely accepted. They assume that the eggs are
male till fertilised, and then become female. After the queen-bee is fertilised most of the spermatozoa soon find their way into a small chamber, the spermatheca, near the posterior orifice of the body; it is believed that each egg may be fertilised as it passes the door of this chamber, and that the eggs that produce females (i.e. workers or queens) are so fertilised, but that the eggs that produce drones are not fertilised. Hence it is supposed that the sex is determined by this act of fertilisation, and Cheshire has described what he calls an apparatus for differentiating the sexes. It is also confidently stated that no male honey-bee ever has a father
The facts we have stated as to the sexes resulting from parthenogenetic reproduction in Hymenoptera generally, are extremely opposed to the Dzierzon theory, in so far as this relates to the production of sex. There have always been entomologists[420] who have considered this view unsatisfactory, and the observations of several recent French naturalists[421] are unfavourable to the idea that the sex of an egg is determined by its fertilisation.
There can be no doubt that the queen honey-bee frequently produces males parthenogenetically, and the error of the views we are alluding to consists in taking the parthenogenesis to be the cause of the sex of the individual. It must be recollected that the laying of an unfertilised egg by a fertilised female may be different physiologically from the laying of an egg by an unfertilised female; for, though both have as result an unfertilised egg, it is possible that the fertilisation of the female may initiate processes that modify the sex of the eggs produced by the ovaries, so that though these may produce previous to fertilisation only male eggs, yet after fertilisation they may produce eggs of the opposite sex or of both sexes. In other words, the act of fertilisation may initiate a different condition of nutrition of the ovaries, and this may determine the sex of the eggs produced.
Polymorphism, or Castes.—The question of the causes of the modified individuals forming the various castes of the social
Hymenoptera has been much discussed. These individuals are many of them very different in size and structure from either of their parents, and are also different in their habits and instincts. This difficult subject is far from being completely elucidated. In the case of the honey-bee it is well established that an egg of the female sex can, after deposition, be made either into a queen or a worker-bee by the mode of nutrition—using that word in the largest sense. On the other hand, Dewitz thought that in the case of the ant Formica rufa, the caste—whether worker or winged female—is already determined in the Insect before leaving the egg.[422] Weismann and others associate the caste with some hypothetic rudiments they consider to exist at the very earliest stage of the embryonic, or oogenetic process.
Herbert Spencer says:[423] "Among these social Insects the sex is determined by degree of nutrition while the egg is being formed," and "after an egg, predetermined as a female, has been laid, the character of the produced Insect as a perfect female or imperfect female is determined by the nutrition of the larva. That is, one set of differences in structure and instincts is determined by nutrition before the egg is laid, and a further set of differences in structures and instincts is determined by nutrition after the egg is laid."
Spencer's generalisation is not inconsistent with the facts hitherto brought to light, though it is possible that the progress of knowledge may show some variety as to the periods of the development at which the commencements of the modifications occur
Fig. 339 represents the chief castes, or adult forms, existing in a community of one of the most highly developed of the species of social Hymenoptera, the leaf-cutting ant, Atta cephalotes. We shall, when dealing with Formicidae, enter into some details as to these and other cases of polymorphism.
F 339 Adult forms of Atta (Oecodoma) cephalotes, taken from a nest in Trinidad by Mr J H Hart, 25th June 1895 A, male; B, winged female; C-F, various forms unwinged; C, so-called soldier; D, large worker; E, smaller worker; F, smallest worker or nurse All equally magnified (one and half times)
Our object at present is to bring to the eye of the reader the great diversity of outer form that is believed, rightly or wrongly, to result from the mode of treatment of the young. And we will also take this opportunity of more fully illustrating the remark we made on p. 85 as to the profound distinctions that exist between ants and white ants, or Termites, notwithstanding the remarkable analogies that we shall find to exist in many of their social arrangements.
The analogies we allude to, coupled with the fact that there is a certain general resemblance in outer form between the workers of Termites and ants, and even between the extraordinary castes called soldiers in the two groups, have given rise to the idea that there is a zoological relationship between the social forms of Neuroptera and Hymenoptera. The two are, however, zoologically amongst the most
different of Insects. The external skeleton in Termites is remarkable for its imperfect development, the sclerites being small and isolated, while the segmental differentiation of the body is low (Fig. 225, etc.), so that there is no difficulty in counting the segments. In ants the reverse is the case as regards both these facts, the various segments being most unequal, so that their homologies have only been detected after prolonged studies, while the chitinisation and articulation of the various parts is so complete that the ant may be described as cased in armour, fitting together so exactly that it is difficult anywhere to introduce the point of a needle into its chinks. The wings of the two kinds of Insects are also extremely different. The differences between the modes of growth and development of the two sets of Insects are as profound as the distinctions in their anatomy. Termitidae belong to the division of Insects in which the wings are developed outside the body; Hymenoptera to the division in which they are developed inside the body. In Termites the growth of the individual is slow, and the final form is reached gradually. In the ants the growth is carried on with great rapidity, and during it the Insect is a helpless maggot absolutely dependent on the attentions of its seniors, while the difference in form and structure between the ant-larva and the ant are enormous. Both anatomy and ontogeny are profoundly different in ants and Termites. To these distinctions must be added, as of much importance, the fact that in Hymenoptera only the female sex is modified for the division of labour, while in Termites both sexes undergo this change. Hence it is impossible to suppose that the remarkable analogies that exist between the societies of ants and those of Termites are due to any common origin. It is probably to some similar physiological susceptibilities in the ancestors, at an extremely remote epoch, of both groups that we must look for an explanation of the interesting resemblances in the social lives of ants and Termites.
The Hymenoptera are no doubt one of the largest Orders of Insects, the species of the parasitic tribes being apparently innumerable. No doubt 250,000 species of the Order exist, and possibly the number may prove to be very much larger. Up to the present time 25,000 or 30,000 have been discovered. No remains of Insects of this Order, of
older age than the Lias, have been brought to light; it is indeed doubtful whether the fossils considered to be Hymenopterous of the period referred to are really such.
The Order, as already mentioned, consists of two very distinct subOrders, viz.:—
1. Hymenoptera Sessiliventres.—Insects with the abdomen broad at the base, its first segment not completely amalgamated with the thorax.
2. Hymenoptera Petioliventres or Petiolata.—The abdomen connected with what appears to be the thorax by a slender joint, the posterior part of the apparent thorax consisting of an abdominal segment.
Hymenoptera Sessiliventres.—This group has been variously called Hymenoptera phytophaga, H. securifera, H. sessiliventres, H. serrifera, H. symphyta. We prefer an old term, taken from a character that enables us to recognise at a glance which group a species belongs to. The division or sub-Order may be formally defined as follows:—
Abdomen nearly continuous in outline with the thorax, the two parts having a broad connexion instead of a small highly mobile articulation. Anal lobe of hind wings usually of considerable size. Trochanters ditrochous (transversely divided into two, Fig. 345). Extremity of body of female furnished with saws or boring instruments, usually concealed, in some cases visible in part. Larvae with complex mouth-parts; three pairs of thoracic legs (imperfect in Cephidae and Siricidae), and frequently with numerous abdominal legs, which are destitute of hooks. Food vegetable.
The Insects of this sub-Order never exhibit the highly specialised habits and activity of the better known petiolate Hymenoptera. Though the food in the larval stages is always vegetable, there is considerable variety in the larvae and their habits; some feed in galls, some in the twigs of plants, some in the hard wood of trees and shrubs. The majority, however, live on the leaves of plants. Those that live in wood (Fig. 342, C) resemble in appearance Coleopterous larvae that have similar habits, and those that live on leaves (Fig. 343, A) resemble Lepidopterous larvae that do likewise. There are four families included in the sub-Order, viz. Cephidae, Oryssidae, Siricidae, Tenthredinidae.
The British Sessiliventres—under the name Phytophagous Hymenoptera—have recently been monographed by Mr. Peter Cameron in a series of vols. published by the Ray Society.[424] These contain many figures and many details relating to natural history, in addition to the descriptions of genera and species.
Fam. I. Cephidae—Stem Sawflies.
Slender Insects, with weak integument; free, more or less elongate pronotum; one spine on the front tibia. Larvae living in the stems of plants or in the tender shoots of trees and shrubs.
The obscure little Insects composing this family have slender antennae of peculiar form, composed of eighteen to thirty joints, two of which are short and stout; then come several long joints, with more or less power of movement, the terminal portion consisting of an elongate club of many joints with little power of movement. The pronotum is longer than is usual in the Hymenoptera, and instead of being very closely connected with the mesonotum, it is free and mobile, although its base overwraps the front of the mesonotum. The median plate (i.e. the dorsal plate connecting the thorax and abdomen) is divided to the base along the middle, the divisions being separated by a membranous piece broader behind; the anal
