Insights to host discrimination and host acceptance behaviour in a parasitoid (Diptera: Asilidae): Implications for fitness

The robber fly Mallophora ruficauda is one of the principal pests of apiculture in the Pampas region of Argentina. As adults they prey on honey bees and other insects, while as larvae they are solitary ectoparasitoids of third instar scarab beetle larvae. Females of M. ruficauda lay eggs away from the host in tall grasses. After being dispersed by the wind, larvae drop to the ground, where they dig in search of their hosts. It is known that second instar larvae of M. ruficauda exhibit active host searching behaviour towards its preferred host, third instar larva of Cyclocephala signaticollis. Although the means by which host location occurs has been studied and since superparasitism is a frequent scenario in the field, no information about host discrimination and host acceptance is available. We carried out studies in the field and behavioural experiments in the laboratory to determine if M. ruficauda is capable of quality host discrimination. We also studied if this parasitoid is capable of conspecific detection in order to avoid superparasitism. Finally, we analyzed the conditions under which superparasitism occurs in the field. We report here that the second instar larva of M. ruficauda is able to discriminate the parasitism status of the host by means of chemical cues, but is not capable of detecting conspecifics prior to attacking a host. We also found that the host cannot detect the presence of the parasitoid by means of chemical cues, so that no counter-defense against parasitism occurs. Furthermore, we determined that superparasitism occurs on the heavier hosts, i.e. those with more abundant resources which could harbor several parasitoid individuals. Finally, we discuss the possible implications of larval host location and host discrimination decisions on the fitness of this parasitoid.     

海南省原毛虫虻属一新种：双翅目：食虫虻科

本文记述食虫虻科原毛虫虻属一新种,尖峰原毛虫虻,新种Archilaphria jianfenglingensis sp.nov.。模式标本均采自海南省尖蜂岭,保存于中山大学昆虫标本室。     

Life‐history traits in a parasitoid dipteran species with free‐living and obligate parasitic immature stages

The robber fly Mallophora ruficauda Weidemann (Diptera: Asilidae) is an important pest of apiculture in the Pampas of Argentina. As adults, they prey on honey bees and other insects, whereas the larvae are ectoparasitoids of Scarabaeidae grubs. Females of M. ruficauda lay eggs in grassland where the larvae drop to the ground after being wind‐dispersed and burrow underground searching for their hosts. A temporal asynchrony exists between the appearance of the parasitoid larvae and the host, with the parasitoid appearing earlier than the host. The present study investigates whether a strategy of synchronization with the host exists in M. ruficauda and determines which of the larval instars are responsible for it. Survival patterns and duration of the immature stages of the parasitoid are investigated to determine whether there is a modulation in the development at any time that could reduce the asynchrony. Experiments are carried out to determine the survival and duration of free‐living larval stadia in the absence of cues associated with the host. It is established that the first instar is capable of moulting to the second instar without feeding and in the absence of any cues related to the host, a unique event for parasitoids. Also, the first instar of M. ruficauda moults to the second stage within a narrow temporal window, and the second instar never moults in the absence of the host. After parasitizing a host, the second instar has the longest lifespan and is the most variable with respect to survival compared with the rest of the instars. All larval instars, except for those in the last (fifth) stadium, have a similar rate of mortality to that of second‐instar larvae. Additionally, it is established that the host is killed during the fourth (parasitoid) stadium and that the first‐ and fifth‐larval instars develop independently of the host. Finally, possible mechanisms that could aid in compensating for the asynchrony between the parasitoid and the host, promoting the host–parasitoid encounter, are discussed.     

Dipteran predators of Simuliid blackflies: a worldwide review

Haematophagous female blackflies (Diptera: Simuliidae) are serious biting pests and obligate vectors of vertebrate pathogens, namely filarial Dirofilaria, Mansonella, Onchocerca and protozoal Leucocytozoon. Immature stages of Simuliidae inhabit lotic waterways, the sessile larvae filter-feeding and often forming a large proportion of the benthic biomass, usually aggregated in well-oxygenated sections of streams, rivers, waterfalls and spillways. Simuliid control practices depend on larvicidal chemicals, biological products (bacteria, nematodes) and environmental modification. The potential use of predators for biological control of Simuliidae has not been exploited. Predators of Simuliidae include examples of at least 12 families of Diptera and other predaceous arthropods (Crustacea and insects: Coleoptera, Odonata, Plecoptera, Trichoptera), invertebrates (notably Turbellaria), as well as browsing fish. Diptera impacting upon simuliid populations comprise mainly Chironomidae, Empididae and Muscidae, although several other families (Asilidae, Dolichopodidae, Phoridae, Drosophilidae, Scathophagidae) play a significant role as predators. Details of predator and prey species and life stages are presented, by zoogeographical region, including the prevalence of cannibalism among Simuliidae.     

Behavioural plasticity induced by intraspecific competition in host orientation in a parasitoid

1. Accurate measurement of external conditions is fundamental for survival. For parasitoids, in particular, sensing the environmental conditions is key because they are short‐lived animals that must acquire information shortly after emergence. 2. This study investigated whether conspecifics during larval growth can influence and modify the decision to orient to different quality hosts in a parasitoid with an active host‐seeking larva. How the density of conspecifics during growth modifies these decisions was also studied. 3. When larvae were submitted to increases in the intensity of pre‐parasitism competition and then offered different host odours, they increased the orientation to poor‐quality hosts likewise. It was also found that this behaviour is general to orientation to hosts in different physiological states. 4. These results show that pre‐parasitism competition can influence and modulate orientation to poor‐quality hosts when high‐quality hosts are not available.     

Review of the species of Michotamia from China with a description of a new species (Diptera, Asilidae)

Three species of Michotamia are recorded from China. Of these Michotamia aurata (Fabricius, 1794) was previously reported from Hainan and Taiwan. Michotamia assamensis Joseph & Parui, 1995 is recorded from China and Laos for the first time, and Michotamia yunnanensissp. n., is described and figured. A key to the known species from China is provided. A new name, Michotamia subnigra, is given to Michotamia nigra Scarbrough & Hill, 2000, which is preoccupied by Michotamia nigra (Meijere, 1911).     

The ontogeny of host-seeking behaviour in a parasitoid dipteran

The robber fly Mallophora ruficauda is one of the principal apiculture pests in the Pampas region of Argentina. As adults, they prey on honeybees and other insects, while as larvae they are ectoparasitoids of third-instar scarab larvae. Females of M. ruficauda lay eggs in tall grasses. After being dispersed by the wind, larvae drop to the ground, where they dig in search of their hosts. It is known that M. ruficauda larvae exhibit active host-searching behaviour; however, it is unknown which instars are involved in this search. We carried out experiments in the laboratory to determine which larval stages are involved in host location. We report here that the second instar of M. ruficauda orientates specifically toward a source of Cyclocephala signaticollis odour, while first larval instar is indifferent to the host cues. Furthermore, we have determined that second instar larvae are more motivated to initiate exploratory movements than larva of the first stage. So far as we know, this is the first case among parasitoids, where the second instar is responsible for host location. Here we provide relevant information of this parasitoid's host-searching strategy, increasing the available knowledge of this significant apiculture pest.     

Host-seeking behavior in larvae of the robber fly Mallophora ruficauda (Diptera: Asilidae)

The robber fly Mallophora ruficauda is the most important pest of apiculture in the Pampas region of Argentina. Adults prey on honeybees and other insects, while larvae parasitize larvae of scarab beetles, which live underground. Females of M. ruficauda do not search for hosts but instead lay eggs in tall pastures. Once hatched, larvae drop to the ground and burrow underground to search for their hosts. We tested in the laboratory whether larvae of M. ruficauda actively search for their hosts using host and/or host-related chemical cues. We report that M. ruficauda detects its host using chemical cues that originate in the posterior half of the host's body, most likely from an abdominal exocrine structure. This particular host-searching strategy is described for the first time in Asilidae.     

中国三叉食虫虻属的记述：（双翅目：食虫虻科）

本文记述三叉食虫虻属Trichomachimus Engel 11个新种。管三叉食虫虻 Tr.tubus sp. nov.,粉斑三叉食虫虻 Tr.maculatus sp.nov.,红三叉食虫虻 Tr.rufus sp.nov.,黑跗三叉食虫虻Tr.nigritarsus sp.nov.,缘毛三叉食虫虻 Tr.marginis sp.nov.,狭三叉食虫虻 Tr.angustus sp. nov.,斜三叉食虫虻 Tr.obliquus sp.nov.,大三叉食虫虻 Tr.grandis sp.nov.,黑角三叉食虫虻Tr.nigricornis sp.nov.,细三叉食虫虻 Tr.tenuis sp.nov.,长三叉食虫虻 Tr.elongatus sp. nov.,分布于我国四川、云南、西藏横断山地区。