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Hemiptera-Truebugs-this is an extremely large order of insects and many are important pests of crops. Only the families Cimicidae and Reduviidae are blood-sucking however and so of any interest here.
C.lectularius does not remain on its host when not feeding. They are negatively phototactic and during the day will remain hidden in any small cracks or crevices. They are able to locate their hosts by temperature and carbon dioxide concentrations although the distance over which these stimuli can be sensed and responded too is not clear at present. Mating in C. lectularius is a rather long process which is divided into three stages. The male bedbug seems to have no other mechanism of distinguishing a female other than by trial and error, although it is able to recognise its own species over a distance of 10-15mm. If a female is found then the first stage called spermalege occurs. This involves penetration by the male into the ectospermalege which is adjacent to the ectospermalege. It takes the sperm approximately 30 minutes before they become mobile. Once mobile they move forward into the haemocoele, a process that takes some three to four hours. This movement into the haemocoele is the second stage. The spermatozoa then penetrate into the seminal receptacle and eventually move up the oviduct wall. The egg is fertilised in the ovariole before the chorionic membrane is formed. This is the third stage called the intragenital phase. This technique of insemination may serve to provide nutrients to the female. This may be important if feeding by the female has been intermittent as egg production will draw on her reserves. Eggs are laid away from the host in the places where the adults reside during the day. They are about 1mm in length and oblong, being laid singularly. When a female is able to take a blood meal twice a week egg laying will be continuous. This means that as a batch of eggs, six to nine usually laid singularly, are oviposited as her first batch she immediately begins to develop another batch. These will be laid the following week and an average of six to seven eggs per week are then laid for around 13 weeks. After 13 weeks fecundity seems to fall rapidly. Development and hatching occurs in around five days at room temperature with a minimum temperature of 130C being needed, although egg laying can vary quite considerably with temperature and relative humidity. The order is a hemimetabola group and so nymphs hatch from the eggs. Within 24 hours of emerging from the egg the first instar will feed and a similar timescale is seen after moulting and the next blood meal. Feeding is quite a lengthy process taking between five and ten minutes. As with many blood feeding insects a anticoagulant is present in the saliva and is injected into the host prior to feeding, this stops the blood from clotting whilst feeding. Also present within the salivary glands are haemolysins which help to digest the blood meal. During feeding the nymphs body weight increases dramatically, and a blood meal of five times their initial body weight is not uncommon. There are five nymphal instars and adulthood can be reached in three weeks at 300C. Adults are able to sustain long periods of not feeding with one report of C.lectularius not taking a blood meal for 550 days. This also shows that the bedbug is long lived and so populations can expand to plague proportions.
Within this family is the subfamily Triatominae. This contains 128 species all of which are obligate blood feeders. Of these
a 102 species are found in the Americas. A variety of vertebrate hosts are fed upon and the bugs live in close association with their
hosts often in nests of birds or the bedding and burrows of mammals. The main species that are of relevance here are Triatoma infestans
and Rhodnius prolixus although this latter species is of lesser importance. The range of T. infestans extends through Argentina,
Bolivia, Brazil, Chile, Paraguay, Peru and Uruguay. This species is still expanding its range, probably with human help from non-intentional
transfer into new areas on belongings and building materials. Adult insects are also capable of flight which is used for dispersal locally.
Other than being important medically to humans, as they are vectors of Trypanosoma cruzi the bugs will feed on chickens, goats, dogs
and guinea-pigs. Some species are day feeders but the majority are nocturnal. In domestic animals such as cats and dogs T. cruzi infection
result in clinical signs but they more usually become hosts without any clinical signs. Although trypanosomes are of huge importance, those that
are most important from a veterinary view point are transmitted by various biting flies and so are dealt with under the Diptera
section at this site.
I wish to thank Prof. Carlos Brisola Marcondes for comments on Triatomines.
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