larvae on drugs??!

[ROBERT BUTCHER]

Sally,
 ive seen one of these postings before yours but missed the first 
(originating thread). So if the below point is of-track / 
irrrelevant to the thread then i apologise now, sorry! 

> I've heard stories about spraying foliage with antibiotics intended for 
> fish and obtained from pet shops.

Fair enough, but im not sure why this would be done, unless this is 
aimed at a rather crude, and probably ineffectial, biological control 
of aphids (Homoptera) rather than leps, because most of these 
antiobiotics are not stable at ambient temperature in water or light 
(i.e. when sprayed onto the tree!!), and so the time window for 
erradicating microbes associated with the phytophagous insect 
(plant eating) is too short.

 However, if this thread started about growing insects with 
antibiotics (see above disclaimer / apology), then certainly the 
growth on articial diets of many leps involves the (optional) 
addition of antibiotics, such as tetracycline hydrochloride (possibly 
one of the fish antibiotics you mention, which is sold in veterinary 
preparations under various other names), propionic acid and 
fungicides such as methyl-4-hydroxy benzoate (nipogin), as indeed 
does artificial media for diptera (including the good old friut fly, 
Drosophila melanogaster). The purpose of such is not to rid the 
insect larvae of microbes, or to provide pathogen free imago (adult) 
insects (as opposed to antibiotic administration to cows for beef or 
milk production), but to prevent these microbes 'outcompeting' the 
insect larvae in the artificial diet substrate. In a similar manner, 
where appropriate, many lep culturers who are not using one of the 
above homogenised and autoclavable (sterilisable) media but whole 
plant leaves, will often blanch the leaves in boiling water, or 
immerse them in hypochlorite solution (bleach, domestos, chloros etc) 
first in order to prevent / reduce the risk of introducing pathogenic 
viruses like GV, or bacteria like BT,  to the cultures.

Thus the aim is not to "cleanse" the insect larvae or imago of 
microbes, and indeed the concentration of antiobiotics etc used in 
the larvael food is often too low for erradication of gut or 
intracellular microbes, or they are comprised of bacteriostatic 
agents (prevent growth of  the microbe so the infection level remains 
the same), rather than bacteriocides (kills the bacteria, and so 
erradicates the "infection"). Indeed, "curing" insects of natural 
parasites can be risky in that you may reduce the fitness of the 
"cured" host since such microbes may be needed as "symbionts" in food 
digestion or assimiliation (famous example is of course the 
intracellular bacteria genus Buchneria in Aphids), semiochemical 
production etc etc, and in one known (so far) case of leps, the Asian 
corn borer moth, (Ostrinia furnacalis), and many parasitic wasps 
(Hymenoptera), they may be involved in  sex determination  via 
feminising genetic males (so infected males actually develop as 
females, and all females develop as females, leading to a female 
biased sex ratio and males only exist from uninfected male zygotes 
(laid eggs), or those at an infection level below a threshold 
value), or inducing thelytokous parthenogenesis (no males, females 
lay fertile progeny without mating which all develop as females that 
do the same, and so on), respectively.
 just my two pence worth
 Cheers
 Rob
Robert Butcher,
Evolutionary and Ecological Entomology Unit,
Department of Biological Sciences,
Dundee University,
Dundee, DD1 4HN,
Tayside, Scotland,
UK.
Work Phone:- 01382-344291 (Office), 01382-344756 (Lab).
Fax:- 01382-344864
e-mail:- r.d.j.butcher at dundee.ac.uk