Phylogeny and Classification

Hymenoptera appear to be relatively isolated from other endopterygotes, and speculations on the origin of the group have been widely divergent. In certain of their features, for example, the large number of Malpighian tubules, they resemble orthopteroid insects, and more than one author has suggested that the order evolved from Protorthoptera, implying a diphyletic origin of the endopterygotes. More frequently, on the basis of many common morphological features and habits possessed by Mecoptera and primitive Hymenoptera, it has been concluded that Hymenoptera form the sister group to the panorpoid complex. Separation of the two probably took place in the Upper Carboniferous period because the earliest fossil Hymenoptera, from the Middle Triassic, are already well developed and clearly assignable to the recent family Xyelidae. Fossils belonging to other symphytan families were present in the Upper Triassic and Jurassic periods, by which time the phytophagous Symphyta had undergone a wide radiation associated with the evolution of pteridophytes, gymnosperms, and other non-flowering vascular plants (Gauld and Bolton, 1988). A few Apocrita (Proctotrupoidea) have also been identified in Middle Jurassic deposits, but the great expansion of this suborder did not occur until the Cretaceous, in which period representatives of all extant superfamilies of Aculeata and Parasitica were present.

It is generally accepted that Apocrita evolvedfrom Symphyta. However, most Symphyta feed on plant materials of various kinds (Jervis and Vilhelmsen, 2000), and the evolution of the primitive Parasitica from such a group has been the subject of much discussion (reviewed by Malyshev, 1968). On different occasions all the major symphytan superfamilies have been suggested as being ancestral to Apocrita. Both morphological cladistic analyses (Ronquist et al., 1999; Vilhelmsen, 2001) and molecular studies (Dowton and Austin, 1994, 1999) indicate that the sister group is to be found in the Siricoidea, either the Orussidae or the Siricidae. Perhaps the former is more likely, as the larvae of modern orussids prey on the burrowing larvae of horntails and beetles (see under Siricoidea). What remains speculative, however, is how the endophagous habit of the ancestral orussid larva evolved toward facultative, then obligate zoophagy, that is, the development of the parasitoid life style. Equally fascinating is how females evolved the ability to seek out the eggs and/or larvae of their hosts. It is evident that the parasitoid habit has evolved on several separate occasions because the Parasitica is clearly a paraphyletic group (Ronquist, 1999; Ronquist et al., 1999). Though members of the majority of Parasitica are parasitoids, in the Cynipoidea and Chalcidoidea many species have reverted to a phyophagous habit, becoming gall formers.

The majority of Hymenoptera have proceeded beyond this stage. In these forms (the Aculeata) the ovipositor took on a new function as a sting for paralyzing (though not killing) the prey. The advantage of this was twofold. First, the prey remained "fresh" while the larva consumed it, and second, the immobile prey could not carry the parasitoid into a different, perhaps inhospitable habitat. This phase in hymenopteran evolution is seen in the extant Chrysidoidea.

From such an ancestral group of paralyzers, the recent groups of higher Aculeata evolved. Two major lines of evolution can be distinguished. In the line that led to the solitary and social wasps (Vespoidea), the insects began to construct special cells in which to place the prey and lay their eggs, presumably to increase the chances of the offspring's survival. However, in one family of vespoids, the ants (Formicidae), an important change occurred. Primitive ants are carnivorous or feed on animal products, especially honeydew, but higher forms are secondarily phytophagous and live on plant tissue, seeds, or fungi. This dietary change was perhaps a response to the increased difficulty of obtaining sufficient animal food as the size of a colony grew. In the second major line, leading to the bees (Apoidea), there was again a trend toward a change in diet from a carnivorous one to one in which plant products, namely, pollen and nectar, were stored, also in special cells, to provide food for the developing larvae. A possible phylogeny of the Hymenoptera is shown in Figure 10.22.

The Hymenoptera have traditionally been arranged in two suborders, Symphyta (Cha-lastogastra) and Apocrita (Clistogastra), and while this arrangement is continued here, it

FIGURE 10.22. A possible phylogeny of the Hymenoptera.

should be noted that the Symphyta is a paraphyletic group (Ronquist, 1999; Vilhelmsen, 2001). In contrast, the monophyletic nature of the Apocrita is widely accepted. Further, the long-standing division of the Apocrita into the infraorders Parasitica and Aculeata can no longer be retained because, as noted above, the former group is paraphyletic. Within the monophyletic Aculeata, there is still disagreement as to the major taxa, some authors splitting the group into as many as seven superfamilies, while others recognize only three (see Gauld and Bolton, 1988).

Suborder Symphyta

In adults of the suborder Symphyta the abdomen is broadly attached to the thorax, and there is no marked constriction between the first and second abdominal segments. Larvae have a well-developed head, as well as thoracic, and, in most species, abdominal legs.

Superfamily Xyeloidea

Xyeloidea form a small (50 species) and extremely primitive superfamily containing the single family XYELIDAE. Adults feed on flowers and have a generalized wing venation. Larvae are found in flowers and have prolegs on all abdominal segments. The family has a holarctic distribution, with most species in North America.

Superfamily Megalodontoidea

The primitive superfamily Megalodontoidea includes two small families, the PAM-PHILIIDAE (170 species, holarctic) and MEGALODONTIDAE (45 species, palearctic). Adults feed on flowers, while larvae, which lack prolegs, live gregariously in webs or rolled leaves.

Superfamily Tenthredinoidea

Tenthredinoidea form a very large and likely paraphyletic group with diverse habits. Females have a sawlike rather than a boring ovipositor and are commonly called sawflies. More than 3000 species belong to the cosmopolitan (except Australia) family TENTHREDINIDAE. Adults are often carnivorous. Parthenogenesis is common, and larvae are usually caterpillarlike in form and habits. A few are leaf miners and apodous. Some species are economically important, for example, Nematus ribesii, the imported currant worm (Figure 10.23A), and Pristiphora erichsonii, the larch sawfly. Some 800 species of the primarily tropical and warm temperate family ARGIDAE have been described. Larvae of some species are gregarious, living under a silken cover; others are leaf miners. Females of some species protect their offspring. The PERGIDAE (400 species) are primarily found in Australia and Central and South America. Larvae are usually gregarious feeders on foliage, rarely leaf miners. Some eucalypt-feeding Australian species accumulate eucalyptus oils in a special gut diverticulum and regurgitate these when disturbed. Other families, which are not large but contain economically important species, are the mainly holarctic and oriental CIMBICIDAE (130 species, including Cimbex americana) (Figure 10.23B), which defoliate various broad-leaved trees, and the holarctic DIPRIONIDAE (conifer sawflies) (90 species) (Figure 10.23C), which include several of North America's most important forest pests (Neodiprion spp. and Diprion spp.).

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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