**7. Biological control agents and sterile insect technique**

Addressing the needs of the increasing human population will require a 60% increase in global food production by 2050 [174]. Insects could aid in achieving this objective by providing food production [19, 164] as well as pollination service (see Section 4) and biological control of pests [175].

Biological control is a method of controlling pests such as arthropods, weeds, and plant diseases using predator (e.g., ladybugs to control aphids [176], herbivorous, or parasite species [175]). Parasitoids are among the most widely used biological control agents (e.g., [177, 178]). In these species, female deposits its egg inside or outside a host where emerged parasitoid larva continues to feed resulting in the host death [178–180]. This parasitic way of life is used by humans to target hosts that are pests. Whiteflies parasitoids (Hymenoptera, Aphelinidae, Encyrtidae, Eulophidae, Platygastridae, Pteromalidae, and Signiphoridae) are an example of insects used in greenhouses to control major crop pests (i.e., the whiteflies; Hemiptera: Aleyrodidae) [177, 180]. As many other parasitoids (e.g., fly *Eucelatoria*, the beetle *Chrysolina*, and the wasp *Aphytis*), they are massively produced in captive conditions by humans before being shipped across the world [180]. The full control of their life cycle by humans is needed in order to ensure that the production (i) matches with the appropriate release dates when susceptible host species is at a suitable phase of development [181] and (ii) is available on a yearlong basis to response to demand across the world [178, 182].

The sterile insect technique (SIT) is an alternative approach to control main pests (e.g., [183–185]) or disease vectors (e.g., [186–188]). This method implies to massively release sterile males (sterilized through the effects of irradiation on the reproductive cells) of an insect species into a target environment to compete with wild males for reproduction [183–185]. Ultimately, mass releases allow limiting offspring production of a particular pest and promoting its eradication (e.g., [184]). Mass-rearing production with a life cycle fully controlled by humans is needed to produce the large quantity of insect required by SIT [183].

The required full control of life cycle of pest insects for SIT or biological control agents means that an advanced domestication process is reached (up to 5 since some patented strains are available [189]). In the context of SIT, several studies have investigated the differences between wild and mass-produced males in order to ensure that released sterile males are able to compete with wild males (e.g., [183, 190]). These studies show that the domestication process has triggered several ecological and behavioral divergences between produced and wild populations as well as a decreased fitness of produced populations in the wild (e.g., [183, 190]).

### **8. Insects as pets**

[160, 161]. *Kerria lacca* (Hemiptera, Kerriidae) is one of the main species used for lac production [160, 161]. Its life cycle is similar to *D. coccus* with winged males and wingless sessile females that parasite several hundred host plants [161, 162]. For several centuries, lac yields were collected from the wild on infested host plants by local human populations [161]. During the nineteenth century, the increase of exportation from Asia triggered the development of artificial inoculation and mass production [161] through a domestication history that can be interpreted as a prey pathway (i.e., human control on the species was triggered by the need of increasing lac supply). Similarly to *D. coccus*, the domestication process of *K. lacca* is at an early stage (level 3, **Figure 1**) since the current production involved only host plant, lac crop,

Humans have been eating insects for millennia [58, 163]. However, human entomophagy is a long-standing taboo in westernized societies [19, 58, 164]. This can explain why insect farming for human food supply has been largely absent from the main agricultural innovations and domestications with few exceptions such as honey bees, silkworms (i.e., pupae is a by-product of silk production), and scale insects [19, 73]. Yet, more than 2 billion of people eat insect regularly since there are a source of protein, fat, vitamins, and minerals frequently stored and sold in developing countries (review in [73, 164]). Across the world, more than 2000 insect species are considered as edible for human food or animal feed [19, 58, 164, 165]. Beside food,

insects provide many natural products for drugs to treat human diseases [166, 167].

Overall, the most commonly consumed insects by humans or livestock/pets are beetles (Coleoptera) (31%), caterpillars (Lepidoptera) (18%), bees/wasps/ants (Hymenoptera) (14%) as well as crickets (Orthoptera) (13%) [19, 58, 73, 163–165]. Most of these insects, as well as those used as entomoceuticals, are harvested in the wild [163] but some of these species are farmed for sale and profit [19, 73]. Currently, commercially farmed insects include (i) the house cricket (*Acheta domesticus*), the palm weevil (*Rhynchophorus ferrugineus*), the giant water bug (*Lethocerus indicus*), and water beetles (various species of Coleoptera) for human consumption [58, 168, 169] and (ii) bees, wasps, flies, butterflies, moths, and cockroaches for drug production [167]. Even in small-scale production in developing countries [19], their production implies that their life cycle is controlled by human in captive conditions isolated from their wild counterparts in order to meet regulations about human food production (i.e., hygienic standards, sterile conditions) as well as limiting pathogen spillover from/to the wild [19, 164, 169–171]. Such conditions are conductive for an advanced domestication process (Level 4, **Figure 1**) through a directed pathway. Conversely, other species are produced through an increasing human manipulation of their environment to increase insect yields and to ensure their long-term availability as food [172]. For instance, edible social wasps (Hymenoptera, Vespidae, *Vespula flaviceps,* and *V. shidai* in Japan) are traditionally managed by keeping wasp nests collected in the wild in hive boxes during one season to improve yields [173]. However, current attempts to improve the practice involves efforts to maintain new queens in captive condition over several generations [173], paving the ways to a prey domestication pathway.

and lac pest management.

46 Animal Domestication

**6. Farmed edible and medicinal insects**

Archeological pieces of evidence show that insects have been used as pets for centuries [191]. Nowadays, crickets, grasshoppers, beetles, cockroaches, silkworms, ants, honey bees, bumble bees, mantises, and stick/leaf insects are bred by humans as a pleasing activity or for teaching purpose [192–194]. Conversely to vertebrates [8, 195–197], there is no, to my knowledge, scientific literature addressing the domestication of pet insects. However, some of these pet insects are produced for other purpose such as honey bees, silkworms, and house crickets for which a domestication process is acknowledged (see previous sections). For other species, such as hissing cockroach (*Gromphadorhina portentosa*), mass/small-scale, and/or amateur production are practiced [198–202]. As for other "exotic" pets (e.g., [18]), these productions involve (i) a full control by humans on the life cycle in captive conditions since a large part of the production is completed out of the species native range and (ii), thus, an advanced domestication process (level 4, **Figure 1**).

is that insect domestication for human food supply has been largely absent from the agricultural development with few exceptions [19, 73]. Moreover, it is likely that insect domestication study has been hindered by the complexity and the subjectivity of the definition of domesticated species (e.g., for *A. mellifera* [10, 16, 47, 117–119, 58, 89, 102, 110, 114–116]). The difficulty of defining a threshold along a continuous process is a common problem in biology (see similar debate about the status and the process for the species status *versus* speciation in [231–233]). Consequently, the study of the process is often set aside or eluded due to debates on a particular threshold. In insects, many scientific articles or books (e.g., [234]) have analyzed or reviewed the breeding/productions of various insect species without explicitly describing these processes as domestication. Yet, the human control on the life cycle (i.e., on individuals' life cycle in noneusocial species or on superorganism's life cycle in honey bees) of most produced insect species is congruent with a domestication process (**Figure 1**; *sensu* [12]). Since a large number of insect populations are produced in captive conditions isolated from their wild counterparts (**Figure 1**), many species can be considered as undergoing a domestication process. Moreover, new domestication processes can be expected in the near future due to current challenges to increase human food/sanitary security (e.g., [19, 164, 175, 186–188]) or to address new demands for pets (i.e., similar development to the ornamental

Insects: The Disregarded Domestication Histories http://dx.doi.org/10.5772/intechopen.81834 49

Domestication events in insects are no less complex than in crops and vertebrates. Domestication histories can involve (i) one (e.g., silkworms [61]) or several (e.g., in honey bees and bumble bees [113, 139]) domestication events and (ii) one (e.g., bumble bees [139]) or potentially several domestication pathways (e.g., honey bees). In most insect species (i.e., except for few extreme cases such as silkworms), different populations of a particular taxon can reach different degrees of progress in the domestication process (e.g., from wild status to an advanced domestication level in *B. terrestris*). Gene flow between populations at different domestication degrees is commonly observed in insects [59, 65, 119] but they do not hinder development of

Some insect species undergo domestication processes for several centuries (e.g., *B. mori* and *A. mellifera*; [57, 59, 60, 63, 89, 104, 105]), while domestications of most insects produced as biological control agents, pets, and laboratory organisms, or for SIT strategies and entomoceuticals' production have been recently initiated. These recent domestications have been made possible thanks to the advances in technology of captive environment control and animal food production since the nineteenth century [1]. Indeed, most insect domestications are thought to follow a directed pathway, which requires rapidly a full control of life cycle by humans in man-controlled environments. This implies the use of efficient environment and food control technologies. Technological advances have made possible or easier the domestication of species, which could not be domesticated in the past, paving the way to a new wave

As for vertebrate species (see review in [1, 12]), some intrinsic features can hinder the development of domestication processes: (i) a diet that cannot be easily supplied by humans (e.g., oligolectic bee species feeding only on few plant species), (ii) long life-cycle (e.g., periodical cicadas that spend most of their 13- and 17-year lives underground at larval stage), (iii) bad

fish trade (e.g., [18, 235–237])).

**10.2. Domestication patterns in insects**

domestication syndrome (see next section).

of domestication (similarly to aquatic species [28]).

#### **9. Insects for laboratory research**

Animals are widely used as model species in biology and biomedical sciences. Some insect species have been used for laboratory experiments for several decades (e.g., silkworms, honey bees, and other species [54, 203, 204]), especially the fruit flies (*Drosophila* spp.) [205–207].

*Drosophila* species first entered laboratories about 1900 and are now standard laboratory animals [208, 209]. As they become an instrument for scientific production, *Drosophila* have been massively produced in laboratory conditions in which life cycle, feeding, and mating are highly controlled by humans [208, 210–212]. This human control along with the strain development and artificial selection for particular purposes [208, 213–216] reflect an advanced domestication process of some populations (level 5, **Figure 1**), while there are many wild populations (e.g., [206, 217, 218]).

Conversely to most other insect species, domestication of *Drosophila* populations has been the focus of several studies since it has been considered as a model system to understand the consequences of the domestication process on genomes and phenotypes [219]. Indeed, fruit flies are easy and cheaply to bred and have a rapid generation time (i.e., at least a dozen generations per year) [206, 220]. This allows comparing several populations that have or not been subject to different domestication histories (e.g., [221–223]) or even monitoring evolutionary trajectories of population undergoing a domestication process since their foundation from the wild [219, 224–226]. This has allowed studying domestication process in well-defined laboratory experiments with replication and specific environmental controls for several *Drosophila* species. An overview of these experiments allows highlighting the domestication consequences for *Drosophila* taxa. Different studies highlight that "domesticated" populations display genetic specificity and accumulation of deleterious mutations, inbreeding depression as well as increasing of fertility, tameness, and manageability due to selection for humanaccommodating phenotypes and/or the relaxation of selection on traits adapted in nature [219, 220, 222, 227–230]. Moreover, the evolutionary convergence is observed between longestablished laboratory populations [219, 220, 222, 227–230].
